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Program JPLCLOCK NASA/JPL Multimission Computer Control Center Clock (C) Copyright David H. Ransom, Jr., 1991 All rights reserved. Version 9128 July 05, 1991 by David H. Ransom, Jr. Rancho Palos Verdes, CA RPV ASTRONOMY BBS (213) 541-7299 (310) 541-7299 [November, 1991] Program JPLCLOCK Multimission Control Center Clock Page i TABLE OF CONTENTS ----------------- INTRODUCTION ......................................................1 JPLCLOCK FEATURES ............................................1 PROGRAM DESCRIPTION ...............................................5 JPLCLOCK HARDWARE AND SOFTWARE REQUIREMENTS .......................7 JPLCLOCK FILES ....................................................7 STARTING PROGRAM JPLCLOCK .........................................9 JPLCLOCK Command Line Options ................................9 Setting UTC Zone and Daylight Flag ...........................9 JPLCLOCK MAIN CLOCK DISPLAY .......................................12 JPLCLOCK MAIN MENU ................................................16 F1 Program Information .....................................17 F2 Set LOCATION CLOCKS .....................................18 F3 Set EVENT/MISSION TIMERS ................................20 Set MISSION/EVENT TIMERS ................................21 Set SELECTED EVENTS .....................................27 F4 Set DAYLIGHT and Defaults ...............................28 F5 Read or Save INI Files ..................................29 INI Files from Other Locations ..........................30 Editing INI Files .......................................30 F6 Self-Calibration using TIMESET ..........................32 F7 Switch TEXT Mode ........................................34 F8 Switch PAGE Mode ........................................34 F9 DOS SHELL (DOS 3.3+ ONLY) ...............................34 F10 TIME SYNCHRONIZATION ....................................35 Configuring Program TIMESET .............................35 Time Synchronization Menu ...............................37 VIEW or SET Time Sync Data ..............................37 TIMESET Time Synchronization ............................38 DOS CLOCK CALIBRATION .............................................39 Setting DOS Time .............................................40 Maintaining DOS Time .........................................41 Calibrating DOS Time .........................................43 Manual Hardware Clock Calibration .......................45 Manual Software Clock Calibration .......................46 USING TEXT MODE ...................................................48 Preparing TEXT Files .........................................49 COMMENTS AND KNOWN PROBLEMS .......................................50 Computer BIOS Problems .......................................50 Monitor Type and Video Adapter Cards .........................50 Computer Processor and Math Coprocessor ......................50 DOS Version and the Shell Feature ............................50 Unstable Hardware or Software Clocks .........................51 Typical Calibration Results ..................................51 Color Variations .............................................52 FUTURE IMPROVEMENTS AND FEATURES ..................................53 UTC AND TIME ZONES ................................................54 JPLCLOCK REVISION HISTORY .........................................56 Program JPLCLOCK Multimission Control Center Clock Page ii JPLCLOCK (NORMAL MAIN CLOCK SCREEN) ║ JPLCLOCK by David H. Ransom, Jr. Version 9126 ║ JD2448422.63779 14 JUN 1991 ■■■■■■■■■■ ╔[ NASA Jet Propulsion Laboratory ]══════════════╗ ┌[ Magellan ]─────────────┐ ║ ║ │ 604 12:18:25 │ ║ ╒═══╗ ╔═══╗ ╒╗ ╔═══╗ ╒═══╗ ╔═══╕ ║ └─────────────────────────┘ ║ ║ ║ ║ ■ ║ ║ ║ ■ ║ ║ ║ ║ ╔═══╝ ║ ║ ║ ╠═══╣ ╔═══╝ ╚═══╗ PDT ║ ┌[ Ulysses ]──────────────┐ ║ ║ ║ ║ ■ ║ ║ ║ ■ ║ ║ ║ │ 251 15:31:10 │ ║ ╚═══╛ ╚═══╝ ╘═╩═╛ ╚═══╝ ╚═══╛ ╘═══╝ ║ └─────────────────────────┘ ║ ║ ║ ╔═══╗ ╒═══╗ ╒╗ ╔═══╗ ╒═══╗ ╔═══╕ ║ ┌[ Galileo ]──────────────┐ ║ ║ ║ ║ ■ ║ ║ ║ ■ ║ ║ ║ │ 616 14:18:25 │ ║ ║ ║ ╞══╣ ║ ╠═══╣ ╔═══╝ ╚═══╗ UTC ║ └─────────────────────────┘ ║ ║ ║ ║ ■ ║ ║ ║ ■ ║ ║ ║ ║ ╚═══╝ ╘═══╝ ╘═╩═╛ ╚═══╝ ╚═══╛ ╘═══╝ ║ ┌[Hubble Space Telescope]─┐ ║ ║ │ 403 14:44:33 │ ╚════════════════════════════════════════════════╝ └─────────────────────────┘ ┌[ GDX Goldstone ]────┐ ┌[ CAN Canberra ]─────┐ ┌[ Gamma Ray Observatory]─┐ │ 165 20:18:25 PDT │ │ 166 14:18:25 │ │ 70 11:55:40 │ └──────────────────────┘ └──────────────────────┘ └─────────────────────────┘ ┌[ JSC Houston ]──────┐ ┌[ MAX Madrid ]───────┐ ┌[ ROSAT Observatory ]────┐ │ 165 22:18:25 CDT │ │ 166 04:18:25 CES │ │ 378 05:30:26 │ └──────────────────────┘ └──────────────────────┘ └─────────────────────────┘ NOTE: Pages ii and iii use the IBM "line drawing" characters as they appear on the display screen. If your printer cannot print these characters, these pages may appear garbled. These line drawing characters are not used elsewhere in this documentation; instead, I substitute similar characters from the normal character set. Program JPLCLOCK Multimission Control Center Clock Page iii JPLCLOCK (SMALL MAIN CLOCK SCREEN) ║ JPLCLOCK by David H. Ransom, Jr. Version 9127 ║ JD2448436.59025 28 JUN 1991 ■■■■■■■■■■ ╔[ NASA Jet Propulsion Laboratory ]══════════════╗ ┌[ Galileo ]──────────────┐ ║ ║ │ 522 15:09:58 │ ║ 179 19:09:58 PDT 180 02:09:58 UTC ║ └─────────────────────────┘ ║ ║ ╚════════════════════════════════════════════════╝ ┌[ Magellan ]─────────────┐ │ 780 18:09:58 │ ┌── SELECTED EVENTS ───┐ ┌── PRIORITY EVENTS ───┐ └─────────────────────────┘ │ │ │ │ ┌[Hubble Space Telesc]─┐ ┌[ Test 6 ]────────────┐ ┌[ Ulysses ]──────────────┐ │ 417 13:36:06 │ │ 0 00:24:08 │ │ 265 08:23:58 │ └──────────────────────┘ └──────────────────────┘ └─────────────────────────┘ │ │ │ │ ┌[Gamma Ray Observato]─┐ ┌[ Test 5 ]────────────┐ │ 84 10:47:13 │ │ 0 00:24:18 │ └──────────────────────┘ └──────────────────────┘ └──────────────────────┘ └──────────────────────┘ ┌[ GDX Goldstone ]────┐ ┌[ CAN Canberra ]─────┐ ┌[ Gamma Ray Observatory]─┐ │ 179 19:09:58 MST │ │ 180 13:09:58 │ │ 84 10:47:13 │ └──────────────────────┘ └──────────────────────┘ └─────────────────────────┘ ┌[ JSC Houston ]──────┐ ┌[ MAX Madrid ]───────┐ ┌[ ROSAT Observatory ]────┐ │ 179 21:09:58 EST │ │ 180 03:09:58 CES │ │ 392 04:21:59 │ └──────────────────────┘ └──────────────────────┘ └─────────────────────────┘ NOTE: Pages ii and iii use the IBM "line drawing" characters as they appear on the display screen. If your printer cannot print these characters, these pages may appear garbled. These line drawing characters are not used elsewhere in this documentation; instead, I substitute similar characters from the normal character set. Program JPLCLOCK Multimission Control Center Clock Page 1 INTRODUCTION ------------ JPLCLOCK is a clock and event timer program written especially for use in the NASA Jet Propulsion Laboratory's Multimission Computer Control Center (MCCC) in Pasadena, California. JPLCLOCK provides mission controllers in the MCCC with current JPL time (Pacific Standard or Daylight Time), UTC (Coordinated Universal Time), and DSN (Deep Space Tracking Network) times as well as up to 60 selected mission or event timers. A text presentation mode allows the display of supplementary text and other messages when the program is used for more general applications. JPLCLOCK is copyrighted software; you are hereby granted a non- exclusive license for non-commercial or educational use only. Agencies of the U. S. Government are hereby also granted a non-exclusive license for the use of this program. Use it if you like it, discard it if you don't. There are no warranties of any kind. If you wish to use JPLCLOCK commercially, write for license information. JPLCLOCK FEATURES ----------------- - JPLCLOCK can turn an "ordinary" IBM-compatible personal computer into a precision clock, synchronized to the National Institute of Standards and Technology in Boulder, Colorado or to the U.S. Naval Observatory in Washington, DC. - When used with the NIST or USNO Telephone Time Service, JPLCLOCK can maintain its displayed time to an accuracy of 0.2 seconds or better over extended periods of time. - JPLCLOCK automatically and continuously compensates for the drift of the DOS software clock. - JPLCLOCK can display your local time and Universal Coordinated Time in large, easy to read characters in its Main Window. - JPLCLOCK can display the local time at four additional locations around the world. - JPLCLOCK tracks as many as 60 different missions or events, displaying the Mission Elapsed Time or a countdown to Time Zero for each event. Mission/event times may range from -27 years to +274 years! - JPLCLOCK can display up to four special PRIORITY EVENT timers that automatically select events whose Time Zero is closest to the current time. - All features and events are set by the user so that JPLCLOCK may be easily configured for each installation. - JPLCLOCK can present supplementary text information on as many as 10 successive display screens for news and public information. Program JPLCLOCK Multimission Control Center Clock Page 2 JPLCLOCK Version 9126 was the first limited public release of the program, after a number of beta versions tested by Charles White at the NASA Jet Propulsion Laboratory. Thanks to Charles, a number of interesting features have been added to the early versions, bugs have been squashed, and the program has been tested in the MCCC and elsewhere. Other interested individuals at JPL have also evaluated the program, offered criticism and suggestions, and researched some of the older mission times. Mike Gardner in Sunnyvale has reviewed an early version of my documentation apart and offered his usual constructive criticism. To all of these people, my thanks! Although my initial discussions at JPL envisioned a "simple" program, JPLCLOCK is definitely NOT simple. The original idea was to adapt my program ASTROCLK to the task required in the MCCC. I have indeed borrowed freely from ASTROCLK (as well as from another of my programs, STSORBIT) and this helped get the first versions up and running relatively quickly. As usually happens, the project quickly grew in scope and complexity. Everyone involved, myself included, had new ideas or suggestions. Equally significant, the personal computer is hardly the ideal precision clock, yet JPLCLOCK is intended for the JPL MCCC where accuracy is critical. Making sure that JPLCLOCK will maintain the required accuracy has consumed considerable time and thought. It wasn't long before the source included thousands of lines of code and the documentation grew to over 40 pages. All this in the space of a couple of weeks of my "spare time"! Given the clock drift and accuracy problems inherent in the design of the typical IBM-compatible personal computer, JPLCLOCK would not have been practical without the various time services provided by the National Institute of Standards and Technology (NIST) and the U.S. Naval Observatory (USNO). The NIST radio stations WWV and WWVH provide an inexpensive and convenient means for "ordinary folks" to synchronize clocks and other equipment. The NIST and USNO Telephone Time Services offer a high precision standard time calibration source when such accuracy is required. Every effort has been made to assure that program JPLCLOCK performs its task accurately and reliably. However, while no known errors of any consequence remain, JPLCLOCK is still a young program and it is almost certain that some bugs are yet to be discovered. In addition, there is still much that can be done to further enhance JPLCLOCK, so new versions can be expected from time to time. User comments, suggestions, and bug or problem reports will be appreciated! Programs such as JPLCLOCK take many hours to develop and maintain. While it is not required, I would appreciate your registration of the program; the cost is very nominal and it will encourage me to continue supporting the program. The only other request I make of users is that they take the time to complete and return the confidential questionnaire in file README. The questionnaire gives users a chance to offer comments and suggestions, and lets me know that people use and appreciate JPLCLOCK. For those who are interested in our space program and who have access to a modem, I recommend NASA's SpaceLink Bulletin Board System in Huntsville, Alabama, (205) 895-0028, available twenty four hours per day. NASA SpaceLink, supervised by Bill Anderson of the NASA Marshall Space Flight Center, provides a wealth of information on NASA and its projects. Orbital elements for a Space Shuttle mission are usually available while a mission is in progress. In addition to educational materials, general information on NASA programs and plans, news releases, and graphics images from current and prior spacecraft missions such as Voyager and Magellan, SpaceLink also provides current news and information on missions in Program JPLCLOCK Multimission Control Center Clock Page 3 progress. Mission status reports for all active missions are generated periodically. I regularly call SpaceLink and post files of interest on my own bulletin board system (BBS). Special thanks to Charles White of the NASA Jet Propulsion Laboratory for his comments and suggestions during the development and testing of this program, as well as a fascinating visit to the JPL Multimission Computer Control Center. Like many others, I consider the Jet Propulsion Laboratory to be a unique national resource, unequaled anywhere else in the world. JPLCLOCK is entirely "a labor of love", to repeat a well-worn phrase; to see my software operating in the MCCC where amazing projects such as Voyager and Magellan are controlled is sufficient reward. A brief biographical note: I am a retired physicist and engineer who spent all of his professional life in the world of electronics, data communications and, more recently, computers. As a young man I was actively involved in the early American space program as a contractor for the Jet Propulsion Laboratory, working on projects such as Ranger and Mariner. Perhaps as a consequence of these and the many other remarkable NASA projects directed by JPL, my respect and admiration for The Lab and its people practically knows no bounds. I was also involved with the Mercury, Gemini, and Apollo projects and my interest in space has continued to this day. My experience includes both hardware and software, and I designed and implemented software professionally for many years with considerable success. I have been writing software for IBM-compatible personal computers, usually oriented toward space and astronomy, for a number of years. Since 1987 I have also maintained the RPV ASTRONOMY BBS, a free access bulletin board system with an emphasis on space and astronomy. So successful has my latest "hobby" become that it is threatening to overwhelm my bulletin board system and consume all of my available time just answering the mail! All of my programs are free although I do encourage users to register them for a modest fee. If my software also serves to help spark the interest of young people in science and technology or can be a learning tool at any level, I will have more than achieved my purposes. Two of my programs, ASTROCLK and STSORBIT, have become widely known throughout United States, Canada, and Europe. ASTROCLK is an attempt to consolidate a multiplicity of astronomy and time related programs into a single useful computer tool. My desire to "keep in touch" with our Space Shuttle missions led to the development of STSORBIT, a simulation of the large wall map in Mission Control at the Johnson Space Center in Houston, Texas. STSORBIT eventually found its way (several times) to JPL where it is now often projected in the MCCC during Space Shuttle missions and for other Earth orbiting missions, and was the catalyst for JPLCLOCK. The initial versions of JPLCLOCK were written over a period of several weeks in June of 1991 with close coordination with JPL. Even before the program was "finished" (if such programs are EVER really finished!), JPLCLOCK was being used during a planned power outage as the primary time standard in the Mission Control Center. JPL is also considering use of the program outside the Mission Control Center to help inform Lab personnel and visitors. How useful it may be to others remains to be seen. For current space and astronomy programs and data, as well as the most recent version of this program, call my bulletin board system (BBS). If the BBS has not answered after the fourth ring, hang up, wait TWO MINUTES, then call back; the system has a power controller and if the system is off it takes that long for the computer to start up and do its housekeeping chores. The system now has almost 1000 users and is often busy, so be Program JPLCLOCK Multimission Control Center Clock Page 4 patient. RPV ASTRONOMY BBS (213) 541-7299 IMPORTANT NOTE -------------- The area code for my BBS telephone number is scheduled to change in November, 1991 as the Los Angeles 213 area code is once again split to accommodate Southern California's continuing growth. The new number will be (310) 541-7299. If you do not have access to a modem, you may send US$10.00 to cover materials, postage and handling for a copy of the latest version on disk; please specify 5-1/4" 360K or 3-1/2" 720K disks. JPLCLOCK can be a complex program when all of its features used, perhaps more complex than was originally anticipated. This documentation attempts to completely describe the program and its operation. There may be errors in this documentation, but please read it BEFORE you drop me a nasty note or give up! David H. Ransom, Jr. 7130 Avenida Altisima Rancho Palos Verdes, CA 90274 Program JPLCLOCK Multimission Control Center Clock Page 5 PROGRAM DESCRIPTION ------------------- The NASA/JPL Multimission Computer Control Center (MCCC), located at the Jet Propulsion Laboratory in Pasadena, California, is the "nerve center" where all NASA planetary missions and some Earth orbiting missions are controlled. Other NASA and ESA (European Space Agency) missions may also be supported by MCCC from time to time. The Control Center resembles other similar installations with consoles for each of the controllers and other responsible individuals directing the progress of a mission and coordinating the operation of the NASA Deep Space Network and other critical resources. Operations continue around the clock with a number of missions typically active. Missions active at this time include Voyager 1 and 2, Magellan, Ulysses, and Galileo. Above the main floor of the Control Center and in plain view of all controllers and individuals in the visitors gallery are seven projection screens, five large and two slightly smaller. These screens display television or computer generated images related to missions in progress. For example, NASA Select Television is frequently displayed when it is broadcasting. JPLCLOCK is normally displayed on one of the screens as selected by Control Center personnel. JPLCLOCK displays various time information for the convenience of Control Center personnel. The current local time (Pacific Standard/Daylight Time) and Coordinated Universal Time (UTC, or GMT as it was formerly designated) are displayed in large characters in the program's main window. Below that window are four smaller windows displaying local time at the DSN locations or other selected installations. On the right side of the screen are six smaller windows which display the Mission Elapsed Time for selected missions in progress (green background) or Countdown Time for missions or events due to occur (red background). The background color switches from red to green when the countdown reaches zero or the event occurs. As many as 60 different missions or events may be monitored with these timers. IMPORTANT NOTE -------------- Before using program JPLCLOCK in applications requiring high accuracy, read the section DOS TIME CALIBRATION in this documentation! JPLCLOCK may be operated in two modes: NORMAL and PAGE. The NORMAL mode displays the main window, four location time windows, and from one to six timer windows continuously. The PAGE mode displays the same main window and four location windows but sequences through up to 60 different timer windows using ten different timer "pages". The timer page is normally switched every thirty seconds; however, when any timer on a particular page is within one hour of of "Time Zero", the display will "freeze" on that timer page. As long as events which occur within several hours of one another are arranged on the same screen page, JPLCLOCK will automatically ensure that the timer for each event is displayed from one hour before to one hour after Time Zero. In addition, up to ten screen pages of supplementary text information or messages may be displayed in conjunction with the PAGE mode. When the TEXT mode is active, the program cycles through all of the active timers then switches and presents the text pages in sequence. This real time to Program JPLCLOCK Multimission Control Center Clock Page 6 text to real time sequence repeats indefinitely unless an active timer reaches the plus or minus one hour period around its Time Zero, in which case that timer page freezes as described above. The default JPLCLOCK configuration is arranged for the convenience of the Jet Propulsion Laboratory MCCC. One or more initialization files, files with a file type ".INI" and containing alternate or supplementary time and location data, may also be included from time to time. Manual configuration features are included for setup at other locations. Window titles, mission or event names, and window times are easily configured for the desired location or event. Inactive location or timer windows may be removed from the screen. The current configuration is saved each time JPLCLOCK is run so that the program may be resumed at any time. While the program is running, all keyboard operations are timed so that inattention on the part of the user for more than ten to thirty seconds (depending upon the operation being performed) will result in automatic restarting of the program. JPLCLOCK is intended for a dedicated IBM-compatible computer running MS-DOS version 3.3 or higher. Best performance will be achieved using a 286 or better processor equipped with a math coprocessor chip. However, the program should execute correctly (but perhaps with perceptible delays) using any IBM-compatible computer with or without a math coprocessor chip. For normal use, the program should started from the computer's AUTOEXEC.BAT file so that it is restarted in the event of a power failure. As of June 1991, JPLCLOCK is still a relatively new program. Although all known problems have been corrected, there are doubtless a few minor bugs yet to be discovered. User comments and suggestions are welcome. Future versions are anticipated at periodic intervals as new features are added and/or problems are corrected. Planned features include optional automatic synchronization with compatible external time signals. Program JPLCLOCK Multimission Control Center Clock Page 7 JPLCLOCK HARDWARE AND SOFTWARE REQUIREMENTS ------------------------------------------- JPLCLOCK is written for use on IBM-compatible computers and has only been tested on computers equipped with an 80286 or higher processor. Most of the features should operate correctly on older computers but those features which use the clock/calendar chip, introduced with the AT-class computer and subsequently retrofitted to older computers as an add-on chip or circuit card, may not operate correctly. Several different clock chips have been used on PC and XT machines which are NOT compatible with the AT chip and may not be compatible with program TIMESET. JPLCLOCK requires a modest amount of the computer's memory. The program has not been tested on a machine with less than 640K of main RAM. Although most JPLCLOCK operations are entirely memory resident, program startup, use of program TIMESET, and the DOS shell all require disk accesses. Because of the excessive time delays associated with floppy disk drives, a hard disk is strongly recommended. Even with a hard disk, delays and system software vary considerably and performance may differ from drive to drive. JPLCLOCK assumes DOS Version 3.3 or higher; MS-DOS and PC-DOS are considered equivalent although testing has been performed only on systems using MS-DOS. Limited testing has been performed using a beta version of DOS 5.0 with no problems encountered. The DOS shell feature of DOS, required for use of program TIMESET, is considered unreliable for versions of DOS prior to DOS 3.1. If you have not upgraded to at least DOS 3.3, consider doing so! As discussed in more detail elsewhere, the DOS software clock varies considerably from computer to computer and from one version of DOS to another. Avoid using your favorite TSR (Terminate and Stay Resident) programs when running JPLCLOCK. Several hours of operation with JPLCLOCK will establish whether or not your computer and DOS software clock are suitable for use with the program. If the DOS software clock varies too much with time or temperature it cannot be used with JPLCLOCK and there is no remedy in most cases except to use a different computer. Because JPLCLOCK is a new program (as of Version 9128), user feedback on both problems and successes will be appreciated! The variety and range of quality of hardware and software "out there" is almost unbelievable and it is helpful if I know which brands of hardware and software work or fail. Please take the time to fill out the questionnaire in file README, whether or not you wish to register the program. JPLCLOCK FILES -------------- JPLCLOCK is normally distributed in archived format using either the PAK or ZIP format. The following files are usually included: JPLCLOCK.EXE Main program (required) JPLCLOCK.DOC Documentation (not required) JPLCLOCK.INI Initialization data (optional) JPLCLOCK.MTD Mission Timer Data (optional) JPLCLOCK.MSG Sample TEXT file (optional) JPLFONT.COM Experimental EGA font (optional) README Program Registration (not required) Program JPLCLOCK Multimission Control Center Clock Page 8 Files noted as "(required)" must be in the current default directory for program operation. Files noted as "(optional)" do not need to be in the default directory when JPLCLOCK is operated but may provide additional features or information if present. File JPLCLOCK.MTD contains data for selected missions. If file JPLCLOCK.INI is not present, it will automatically be created the first time the program is executed. Additional MTD files (files with filetype ".MTD", standing for "Mission Timer Data") may be included from time to time with interesting or upcoming events pre-programmed. Other MTD files may be posted periodically on my bulletin board system for upcoming events. Registration of program JPLCLOCK is not required but certainly will be appreciated! See the file README for registration information. JPLCLOCK has required considerable effort to develop and test and your response will encourage me to continue enhancing and supporting the program. As an additional "bonus" for registration, I will send the latest version of JPLCLOCK to you on disk; please specify the disk size desired: 5-1/4" 360K or 3-1/2" 720K (supplied if no disk size specified). Program JPLCLOCK Multimission Control Center Clock Page 9 STARTING PROGRAM JPLCLOCK ------------------------- Before starting program JPLCLOCK for the first time, make sure that all required files are in the current drive and directory (see below). Delete the file JPLCLOCK.INI if it has been created by a previous version of JPLCLOCK or you are using the program at a different location from the one which prepared the file. The format of the INI file may change with new versions and, although the program may read prior versions of .INI files, it is safer to "start from scratch". The INI file also includes specific information related to the local time zone. To start program JPLCLOCK for operation in the NORMAL mode, enter the following command at the DOS prompt: JPLCLOCK As described in the summary of command line options below, you may add the "/M" command line option to the examples above to force monochrome operation on CGA, EGA, and VGA systems. JPLCLOCK Command Line Options ----------------------------- All JPLCLOCK program features (except monochrome operation) may be enabled or disabled from within the program. However, to facilitate use with batch files, certain features may be enabled using "command line options", specific words preceded by the slash ("/"), used when the program is started from the DOS prompt. A command line consists of the program name followed by the desired command line option(s): "JPLCLOCK [option] ... [option]". The following command line options are available: ? (Special option) Displays brief help information to remind users of the principal command line options and then returns to DOS. /M Force monochrome operation. On color monitors, this usually forces white or light white on black background. /SMALL Enables the SMALL main clock window and the additional four SELECTED/PRIORITY timer windows. /PAGE Enables PAGE mode operation with up to 60 Mission/Event Timers displayed in "pages" of six timers each. Default is the non-page mode with only 6 Mission/Event Timers. /TEXT Enables TEXT (and PAGE) mode operation if file JPLCLOCK.MSG is found. Up to ten screen pages of prepared text may be sequentially displayed. Setting UTC Zone and Daylight Flag ---------------------------------- JPLCLOCK must know the correct time and time zone in order to operate Program JPLCLOCK Multimission Control Center Clock Page 10 accurately. The first time JPLCLOCK is executed (or any time the program cannot find the file JPLCLOCK.INI), the program prompts you for your UTC Offset and asks if you are now on Daylight or Summer time: Set UTC TIME ZONE OFFSET and DAYLIGHT FLAG JPLCLOCK must know the difference between your local time zone and Universal Coordinated Time (UTC), also sometimes known as Greenwich Mean Time (GMT). With this information, JPLCLOCK can automatically adjust launch times and dates for your local time zone. In addition, JPLCLOCK must know if you are now on STANDARD or DAYLIGHT (SUMMER) time. First, enter the difference between your STANDARD time zone and UTC in hours. Do NOT include the hour for daylight time if you are now on DAYLIGHT time; it will be entered separately. For most time zones in the United States and Canada, the entries required are: Eastern Standard Time EST -5.00 Central Standard Time CST -6.00 Mountain Standard Time MST -7.00 Pacific Standard Time PST -8.00 Enter UTC Offset (hours) [not set]: -8 Enter Daylight Flag (0=OFF, 1=ON) [0]: 1 The example entries shown above illustrate the required information for Pacific Daylight Time: "-8" for the standard time zone offset from UTC and "1" to signify that Daylight Time is in effect. Enter the information that is appropriate for your time zone. Once the UTC Offset and Daylight Flag information have been entered, these data are saved in file JPLCLOCK.INI and will not be requested again. Not surprisingly, JPLCLOCK relies upon the internal clock in your computer to maintain accurate time. However, not all computer clocks are created equal; some are much more accurate than others and it is difficult to predict that performance in advance. The computer clock was simply not designed as a high precision timekeeping instrument. Further, recent versions of DOS (3.3 and higher) can reset an otherwise relatively accurate hardware clock if the software clock loses time. Just as your quartz watch will keep time most consistently (as opposed to accurately) when you leave it always on your wrist, so too your computer clock will keep time best if it is left on continuously. Time and temperature changes are a quartz oscillator's worst enemy, along with a long term crystal aging effect. Taken together, these effects can cause your clock to lose or gain up to several seconds per day. For reasonably accurate operation, your computer clock should be synchronized against a time standard from time to time. See the sections DOS CLOCK CALIBRATION and TIME SYNCHRONIZATION for additional discussion, especially for installations where high precision is desired or required. Other factors may also affect the accuracy of the computer's clock. One of the most common and severe offenders is Local Area Network (LAN) software; while this can vary depending upon the LAN BIOS and network hardware being used, the networking software in many systems may completely or partially ignore the clock's "time ticks" during network operations. Another frequent offender is high speed communication (usually about 50Kb Program JPLCLOCK Multimission Control Center Clock Page 11 per second or higher) via the serial communications ports, CON1 through COM4; in this case too, time ticks may be lost and the clock will fall behind. Clock problems related to networking or other software can result in time losses up to tens of seconds or even minutes per day! There is no remedy for this situation except to avoid using the software which causes the problem. Once the UTC Offset and Daylight Flag are set, JPLCLOCK continues with its normal startup and displays the title screen (see below). Verify that the current local and UTC time and date (including your local time zone abbreviation if you are located in the United States) are correct before proceeding. JPLCLOCK will start automatically in 10 seconds and the message on the screen will count down during the wait time. No operator action is required if you wish JPLCLOCK to start; you may also press ENTER twice to immediately start the program, bypassing the 10 second delay. JPLCLOCK's full name and the current version are shown on the title screen, followed by the current time and date. At this point the program is awaiting user input; if no keyboard input is detected within 10 seconds, the program will automatically begin operation. Press ENTER to display the Main Menu or ESC to quit the program and return to DOS. All other keys are ignored except that a timed message is displayed at the upper right of the screen reminding the user to press ENTER for the Main Menu. Program JPLCLOCK Multimission Control Center Clock Page 12 Program JPLCLOCK NASA/JPL Multimission Computer Control Center Clock Version 9128 Current time: 20:18:02 PDT 03:18:02 UTC Current date: 06/30/1991 07/01/1991 JPLCLOCK will start automatically in 10 seconds OR Press ENTER for MENU, ESC to QUIT (C) Copyright David H. Ransom, Jr., 1991 All rights reserved. Note both the local time and date (Pacific Daylight Time in the example) and UTC time and date (Coordinated Universal Time). Be sure that ALL time and date items are correct. If not, press ENTER to go to JPLCLOCK's Main Menu and then press F4 to correct the information. IMPORTANT NOTE -------------- If you are using a JPLCLOCK.INI file (or any other INI file) prepared at some other location, your local time and date may not be correct. If all else fails, quit program JPLCLOCK, delete file JPLCLOCK.INI, and restart the program. JPLCLOCK will assist you in setting up the program for your time zone and will create a new JPLCLOCK.INI file for subsequent use. JPLCLOCK MAIN CLOCK DISPLAY --------------------------- The Main Clock display for JPLCLOCK is illustrated on Pages ii and iii above. Two screen layouts are available, selectable either by a command line option or by a Function Key, NORMAL or SMALL. The NORMAL screen provides a large window with special large characters for Local and UTC Times and is recommended when the program will be used on a normal monitor which may have to be viewed from some distance. The SMALL screen provides a smaller window for Local and UTC Times along with up to four additional timers and may be preferred when JPLCLOCK is projected on a large screen. The remaining windows are the same for both screen layouts. The four Location Clocks are below the main window, and the six Mission/Event Timers Program JPLCLOCK Multimission Control Center Clock Page 13 are on the right side of the screen. The Location Clocks and the Mission/Event Timers are separately described in following sections. In addition to these data, the main clock display also includes the program name and version, as well as the current Julian Date (a standard method of day numbering used by scientists and astronomers) and local date (day- month-year) at the upper right corner of the display. The following keys are active while JPLCLOCK is running and the clocks and timers are displayed on the screen: ENTER Stop the main clock display and go to JPLCLOCK's Title Screen. Press ENTER again to go to the Main Menu. See the section below for a description of the available commands at the Main Menu. ESC Quit JPLCLOCK and return to DOS. You will be asked to press ESC again to confirm that you wish to quit the program. If not, press ENTER to resume operation. ALT-F1 Freeze the display. Updating the screen stops EXCEPT that Local and UTC Time will be updated above the Main Window and the word "FREEZE" will flash in yellow above the Mission Timer Windows while the freeze is in effect. The freeze will be automatically released in five minutes, or press ENTER to release the freeze immediately. (Actually, pressing any key except keys which do not generate a character, such as SHIFT, ALT, or CTRL, will release the freeze.) ALT-F5 Change SELECTED/PRIORITY EVENTS display. This key is active ONLY when the SMALL Main Window is active. The choices are: four SELECTED Mission Timers; two SELECTED Mission Timers and two PRIORITY Mission Timers; or, four PRIORITY Mission Timers. Press again for the next arrangement. ALT-F6 Switch between the LARGE Main Window and the SMALL Main Window. Enabling the SMALL Main Window also displays the four SELECTED/PRIORITY Event Timers (as currently selected). ALT-F7 Enable or disable the TEXT mode if the file JPLCLOCK.MSG is present; otherwise, this command has no effect. See the section USING TEXT MODE for further information on this mode of program operation. This command is the same as the F7 command on the Main Menu. ALT-F8 Enable or disable the PAGE mode. If the TEXT mode is enabled when the PAGE mode is disabled, the TEXT mode will also be disabled. This command is the same as the F8 command on the Main Menu. ALT-F9 EXPERIMENTAL COMMAND to enable a special screen font, similar to "Helvetica", for EGA and VGA monitors ONLY. The special font is designed primarily for EGA systems and may not operate correctly on VGA systems. (On one Program JPLCLOCK Multimission Control Center Clock Page 14 VGA system, for example, the last few lines of the screen show a variety of text and graphics symbols when program TIMESET is executed, and these symbols remain on the screen when JPLCLOCK resumes operation.) ALT-F10 Immediately perform TIME SYNCHRONIZATION using the external program TIMESET to call either the National Institute of Standards and Technology (NIST) or the U.S. Naval Observatory (USNO). See the section TIME SYNCHRONIZATION for further information on this command and program TIMESET. This command is the same as the F10+F1 commands on the Main Menu. Four additional timer windows appear on the screen below the Main Clock window when the SMALL Main Window is selected. These are divided into two classes: SELECTED EVENTS and PRIORITY EVENTS. SELECTED EVENTS are just like regular Mission/Event Timers except that they are always displayed; they may be selected from the current Mission/Event Timers by pressing F3+F2 from the Main Menu. PRIORITY EVENTS are those events which have a Time Zero which is within 24 hours of the current time. Three different arrangements of SELECTED EVENTS and PRIORITY EVENTS may be selected by pressing ALT-F5 when the SMALL Main Clock is displayed. These two classes of events are always selected from the available 60 Mission/Event Timers; note that the titles have been truncated because the window width is shorter than the normal Mission/Event Window. The default arrangement displays four SELECTED EVENTS: +--------------- SELECTED EVENTS ----------------+ | | +[Hubble Space Telesc]-+ +[ Voyager 1 ]---------+ #1 | 424 01:38:02 | | 5,051 01:13:54 | #3 +----------------------- +----------------------+ | | #2 +[Gamma Ray Observato]D+ +[ Voyager 2 ]---------+ | 90 22:49:09 3 3 5,066 23:47:54 | #4 +----------------------+ +----------------------+ +------------------------------------------------+ Pressing ALT-F5 once will change the arrangement to two SELECTED EVENTS and two PRIORITY EVENTS: +-- SELECTED EVENTS ---+ +-- PRIORITY EVENTS ---+ | | | | #1 +[Hubble Space Telesc]D+ | | #1 | 424 01:37:27 | | | +----------------------+ | | | | | | #2 +[Gamma Ray Observato]-+ | | #2 | 90 22:48:34 | | | +----------------------+ | | +----------------------+ +----------------------+ Note that only the first two SELECTED EVENTS are now displayed. In this example, there are no active PRIORITY EVENTS and therefore that window area is blank. JPLCLOCK continuously scans all 60 Mission/Event Timers to Program JPLCLOCK Multimission Control Center Clock Page 15 determine if any are less than 24 hours (plus or minus) from the current time. Events which have not yet occurred are shown with a RED background, and events yet to occur are shown with a GREEN background. If any events are found within the 24 hour range, they are sorted in such a way that #1 is that event now closest to Time Zero and #2 is the next closest to Time Zero. The ordering of PRIORITY EVENTS is set dynamically and will change as the time difference between the Time Zero set in the Mission/Event Timers changes with respect to current time. Pressing ALT-F5 again will change the arrangement to four PRIORITY EVENTS: +--------------- PRIORITY EVENTS ----------------+ | | +[ Test Event ]--------+ | #1 | 0 01:38:02 | | #3 +----------------------- | | | #2 | | | | #4 | | +------------------------------------------------+ As described above, the PRIORITY EVENTS are continuously scanned and sorted. With this display arrangement, from zero to four PRIORITY EVENTS may be displayed. In the example shown, the Mission/Event Timer called "Test Event" has been detected as within 24 hours of Time Zero (1 hour and 38 minutes past Time Zero in this case) and is therefore displayed. Program JPLCLOCK Multimission Control Center Clock Page 16 JPLCLOCK MAIN MENU ------------------ Program JPLCLOCK NASA/JPL Multimission Computer Control Center Clock Version 9128 Current time: 20:18:50 PDT 03:18:50 UTC Current date: 06/30/1991 07/01/1991 JPLCLOCK will start automatically in 10 seconds F1 Program Information F6 CLOCK Calibration [OFF] F2 Set LOCATION CLOCKS F7 Switch TEXT Mode [OFF] F3 Set EVENT/MISSION TIMERS F8 Switch PAGE Mode [ON] F4 Set DAYLIGHT and Defaults F9 DOS Shell (3.3+ ONLY!) F5 Read/Save INI & MTD Files F10 Time Synchronization ENTER Resume Program JPLCLOCK ESC Quit Program JPLCLOCK Enter selection: As with the title screen, JPLCLOCK is awaiting user input; if no keyboard input is detected within 10 seconds, the program will automatically resume operation. Note that the Main Menu displays the current status of CLOCK Calibration, TEXT Mode, and PAGE Mode. Press ENTER to immediately resume program operation. Press ESC to quit and return to DOS; the program will request that you press ESC a second time to confirm that you wish to return to DOS. (To resume JPLCLOCK when this message appears, press ENTER.) To go to one of the sub-menus, press the indicated Function Key. The purpose and operation of each menu item is described on the following pages. Program JPLCLOCK Multimission Control Center Clock Page 17 F1 Program Information ------------------------ Function Key F1 displays a brief description of the program and gives the telephone number of my bulletin board system (BBS), RPV ASTRONOMY BBS, in Rancho Palos Verdes, California near Los Angeles. This is a free access BBS which I maintain as a public service. There are nearly 1,000 more or less regular callers, and the system is frequently busy, so please be patient! The BBS computer has a power controller; if the BBS has not answered by the fourth ring, hang up and call back in approximately two minutes. RPV ASTRONOMY BBS (213) 541-7299 (310) 541-7299 [November, 1991] IMPORTANT NOTE -------------- The BBS area code number will change in November, 1991 as the telephone company again splits the Los Angeles 213 area code into two areas. The new number will be (310) 541-7299. Program JPLCLOCK was written especially for the NASA/JPL Multimission Computer Control Center. It provides a main window with local and UTC time, four location clocks usually displaying local time at the NASA Deep Space Network sites in Goldstone, Canberra, and Madrid, and six event timers used to display mission elapsed time or the time for an upcoming event of interest. The current version of JPLCLOCK is always available on my BBS. David H. Ransom, Jr. Program JPLCLOCK Multimission Control Center Clock Page 18 F2 Set LOCATION CLOCKS ------------------------ JPLCLOCK displays from one to four LOCATION CLOCKS. When the program is used in the JPL Mission Control Center, three of the clocks normally display the time for the DSN (Deep Space Network) antenna locations; the fourth location clock may be used for another location of interest or may be left blanked out. The location clocks are numbered #1 through #4 and are located in the lower left portion of the display screen below the main window in the following relative positions: | Main Window | | +------------------------+ +--- +----------+ +----------+ +--- | #1 | | #3 | | +----------+ +----------+ +--- +----------+ +----------+ +--- | #2 | | #4 | | +----------+ +----------+ +--- Each Location Clock displays the local time at the location using the following format (all times in 24-hour notation, HH:MM:SS): 147 13:24:16 PDT --+ -+ -+ -+ --+ | | | | | | | | | +--- Time Zone Abbreviation (if present) | | | | | | | +------- Local Seconds | | +---------- Local Minutes | +------------- Local Hours | +------------------ Local Day of the Year Function Key F2 allows the user to change the name and time zone information for the four location clocks displayed below the main window. If a location name is PRESENT for a given location clock, that clock will be displayed on the screen; if the location name is ERASED (the "Location Name" column for the clock is blank in the display), the clock will NOT be displayed on the screen. The default location clocks are shown below: Uses # Location Name UTC Offset DST ----------------------------------------- 1 GDX Goldstone -8.00 YES 2 JSC Houston -6.00 YES 3 CAN Canberra 11.00 NO 4 MAX Madrid 1.00 NO Enter LOCATION # to change: JPLCLOCK will automatically resume operation if no keyboard input is detected within 30 seconds. Each keystroke resets the 30 second timer. Program JPLCLOCK Multimission Control Center Clock Page 19 Press ENTER to cancel this function and return to the Main Menu making no changes. To continue, enter the number of the location clock to change and press ENTER. Then enter the new location name for that clock: Enter new LOCATION NAME: Press the TAB key to leave the name unchanged for this clock and skip to the time information. Press ENTER to erase the name and remove the clock from the display screen. To enter a new or corrected location name, type the new name and then press ENTER. JPLCLOCK will automatically capitalize the first letter of each word if it is lower case. In order to show the local time correctly for each location, JPLCLOCK must know the UTC Offset for the location; this is the number of hours which must be ADDED to UTC (Universal Coordinated Time) in order to obtain the local STANDARD time for the location. Do NOT include the additional hour if the location is on U.S. Daylight Savings Time; DO include the additional hour if the location is on daylight or summer time but the time changes do not correspond to those used in the United States. See the additional discussion below. Enter New UTC Offset (hours): Press the TAB key to leave the current UTC Offset value unchanged. Press the ESC key to cancel all changes to this location clock. Otherwise, type the new UTC Offset in hours (and decimal parts of an hour if necessary) and then press ENTER. JPLCLOCK will independently adjust each location clock time for U.S. Daylight Savings Time if the special flag in the column "Uses DST" is marked "YES". As a general rule, therefore, respond "YES" if the location is within the United States (including Alaska and Hawaii); respond "NO" if the location is outside the United States. Uses US Daylight (N=NO, Y=YES): IMPORTANT NOTE: When the main Daylight Flag is changed (using F4+F3 from the Main Menu), the appropriate correction will be automatically made for all locations which indicate "YES" in the "Uses DST" column. Locations outside the United States which use daylight or summer time but which change at different times from the United States should indicate "NO" in the "Uses DST" column and must be manually adjusted for each time change. When all of these questions have been answered, the information will be updated on the screen and the user may either continue to another location clock or return to the Main Menu. Program JPLCLOCK Multimission Control Center Clock Page 20 F3 Set EVENT/MISSION TIMERS ----------------------------- One of the most important functions of JPLCLOCK is to be able to display Mission Elapsed Time (MET) or Countdown/Countup Time for a variety of missions and events. MIssion Elapsed Time usually measures the time since the mission was launched and is the primary time measure used for the Mission Timeline, the schedule of planned events and operations; this applies equally to short duration missions such as the Space Shuttle as well as to long duration missions such as Voyager and Hubble Space Telescope. Countdown/Countup Times may be critical events in the progress of a mission, such as scheduled Launch Time or Venus Orbit Insertion for Magellan, and controllers need to be able to judge the time remaining until (or time passed since) specific tasks or operations are to be (or were supposed to have been) performed. JPLCLOCK is able to independently time up to 60 different events or missions using six MISSION TIMER WINDOWS on the display screen and switching from one mission timer "page" to another to display up to ten pages. The mission timer windows are numbered #1 through #6 and are located on the right of the display screen beside the main window in the following relative positions: ---+ +----------------+ | | TIMER #1 | M | +----------------+ a | i | +----------------+ n | | TIMER #2 | | +----------------+ W | i | +----------------+ n | | TIMER #3 | d | +----------------+ o | w | +----------------+ | | TIMER #4 | ---+ +----------------+ ---+ +----------------+ | | TIMER #5 | ---+ +----------------+ ---+ +----------------+ | | TIMER #6 | ---+ +----------------+ Each Mission/Event Timer displays the current time value for that mission or event using one of the following formats (all times are shown as HH:MM:SS, hours:minutes:seconds): 143 13:01:47 The event occurred 143 days plus time ago. When applied to a mission, this format is measured from the time of launch and is known as Mission Elapsed Time (MET) and is used for all mission event planning. Program JPLCLOCK Multimission Control Center Clock Page 21 -16 01:33:19 The event will occur in 16 days plus time. -0 07:44:51 * The event will occur in the time shown and a flashing asterisk denotes less than 24 hours. -0 00:58:29 ** The event will occur in the time shown and two flashing asterisks denote less than 1 hour remains. -0 00:08:14 *** The event will occur in the time shown and three flashing asterisks denote less than 10 minutes remain. Pressing F3 from the Main Menu displays the menu for setting the MISSION/EVENT TIMERS and the SELECTED EVENTS: F1 Set MISSION/EVENT TIMERS F2 Set SELECTED EVENTS ENTER Return to Main Menu Press the Function Key for the desired selection or press ENTER to return to the Main Menu. Set MISSION/EVENT TIMERS ------------------------ Using F1, each Mission/Event Timer may be set to any desired time and date in the past or future over a range of approximately minus 27 years (- 9,999 days before the event) to approximately plus 274 years (99,999 days after the event) referenced to the current time. Given the time scale of interplanetary missions such as Voyager 1 and 2 or Pioneer 11, these time ranges are reasonable and necessary even though it may seem like "overkill" for a 5-day Space Shuttle mission. The Mission Timer Window background color (for color monitors) is RED if the event has not yet occurred and GREEN if the event has occurred. The color switch occurs when the Mission Timer reaches 0 days and 00:00:00 (hours:minutes:seconds). As a special feature to call attention to events about to occur, a single asterisk ("*") appears to the right of the countdown time when the event is less than 24 hours from occurrence; this changes to two asterisks at T minus one hour and to three asterisks at T minus ten minutes. The asterisks are removed once the scheduled event time occurs. When JPLCLOCK is operated in the NORMAL mode, Mission Timers #1 through #6 are displayed continuously; the remaining 54 timers are neither checked nor displayed. However, when JPLCLOCK is operated in the PAGE mode, all 60 Mission Timers are checked and are displayed if a valid time and date has been entered. The Mission Timers are divided into ten pages of six timers each. The pages are numbered 0 through 9; Mission Timers #1 through #6 appear on Page 0, Mission Timers #7 through #12 appear on Page 1, and so forth. If any one of the timers in a given page is valid, that page will be displayed; if no timers in a given page are valid, that page will be skipped. Each page is displayed for 30 seconds and then the program cycles to the next valid page. With active Mission Timers in each of the ten Program JPLCLOCK Multimission Control Center Clock Page 22 pages, it can require up to 5 minutes to complete a full cycle through the timers. When the PAGE mode is active and JPLCLOCK is cycling through all active Mission Timers, a special "bar meter" is displayed at the top right of the Mission Timers. This is a row of ten special square symbols, one for each of the ten Mission Timer pages, which indicates the status of the page. If there are no active Mission Timers on the page, the symbol is GRAY. If one or more Mission Timers on the page is in the countdown mode (the event has not yet occurred), the symbol is RED. If all active Mission Timers on the page are in the countup or Mission Elapsed Time mode, the symbol is GREEN. The current active page is flashing. With up to 60 Mission Timers active in the PAGE mode, it might be easy to overlook an event which is scheduled to occur in the near future. The flashing asterisks described above may help to avoid this situation but JPLCLOCK solves the problem by "freezing" the display on a page if any Mission Timer on that page will reach Time Zero within the next hour. The freeze remains in effect until all timers on that page are either more than one hour before Time Zero or have passed Time Zero by more than one hour. When the freeze is removed, normal cycling is resumed and the program checks for other potential freeze opportunities on each page as it is displayed. IMPORTANT NOTE -------------- If two Mission Timers are on different pages and are scheduled to reach Time Zero at approximately the same time (within two hours), the first timer encountered will enable the freeze for its page and the second timer will not be checked! Some care must therefore be used in selecting events for each page in order to avoid this type of "freeze conflict". Not all Mission Timers on a particular page must be programmed. If the Event/Mission Name is blank, that Mission Timer will not be displayed and its position on the display screen will be blank. The user may therefore arrange both which page(s) will be displayed as well as what position(s) is(are) used to display the active timers on a given page. As noted above, if ALL Mission Timers on a particular page are blank, that page will be skipped. Function Key F3 provides the capabilities to enter, erase, or correct the Mission Timers. The first time F3 is used, Page 0 and the first six Mission Timers will be displayed; subsequent uses of F3 may start on a different page. The Page Number is shown along with the data for the individual Mission Timers on that page. Program JPLCLOCK Multimission Control Center Clock Page 23 # Event/Mission Name Time(UT) Date (MDY) Julian Date PAGE --------------------------------------------------------------- 1 Magellan 15:00:00 10/18/1989 2447818.125000 +---+ 2 Ulysses 11:47:15 10/06/1990 2448170.991146 | | 3 Galileo 13:00:00 10/06/1989 2447806.041667 | | 4 Hubble Space Telescope 12:33:52 05/07/1990 2448019.023519 | | 5 Gamma Ray Observatory 15:22:45 04/05/1991 2448352.140799 +---+ 6 ROSAT Observatory 21:47:59 06/01/1990 2448044.408322 (Home, PgUp, PgDn, ENTER to return to Main Menu) Enter EVENT # to change (1-60): NOTE: The dates and times for Magellan, Ulysses, and Galileo shown above are dummy values entered for testing purposes. Subsequent releases of the program will include the actual values. The reminder enclosed in parentheses indicates the special keys that are active at this prompt: Home Display PAGE 0 PgUp Go to NEXT PAGE PgDn Go to PRIOR PAGE ENTER Return to Main Menu Use PgUp or PgDn to review each of the ten Mission Timer pages or type the number of the desired Mission Timer followed by ENTER to edit that Mission Timer. When a Mission Timer has been selected, a flashing diamond will appear to the left of the Mission Timer number in the display and you will be asked to enter a new MISSION NAME. For the following example, Mission Timer #7 was desired and "7" was typed: # Event/Mission Name Time(UT) Date (MDY) Julian Date PAGE --------------------------------------------------------------- * 7 Voyager 1 03:59:02 10/16/1977 2443432.666000 -+ 8 Voyager 2 19:59:31 08/01/1977 2443357.333000 | 9 | 10 | 11 --+-- 12 (TAB to SKIP, #nn to COPY, ESC to CANCEL, ENTER to ERASE #7 data) Enter #7 EVENT/MISSION NAME: The asterisk shown above will actually be displayed as a flashing diamond to indicate the selected Mission Timer. The reminder enclosed in parentheses indicates the special keys that are active at this prompt: TAB SKIP the name, leaving it unchanged, and continue. ESC CANCEL making changes to this Mission Timer ENTER ERASE all data for this Mission Timer In some cases, you may wish to copy an event from one Mission Timer to another. If the event is simply being moved, you would then go back and erase the original entry; otherwise, the event will appear in multiple Mission Timers (which might be desired for certain important events). The "#nn" format may be used for this purpose by substituting the SOURCE MISSION TIMER NUMBER for "nn". Thus, after selecting the DESTINATION Program JPLCLOCK Multimission Control Center Clock Page 24 MISSION TIMER NUMBER in the previous step, you would enter "C13" to copy all data from Mission Timer #13 to the selected Mission Timer. In other cases, you may wish to prepare a group of related Mission Timers relative to a single time. A sequence of operations following launch or satellite deploy are examples of this situation. To do this, first select the "base time" event and enter its information into a selected Mission Timer. Next, select each successive Mission Timer whose time is relative to the "base time" and use one of the following formats: #nn+ddd/hh:mm:ss #nn+hh:mm:ss #nn-ddd/hh:mm:ss #nn-hh:mm:ss where: # Specifies the COPY syntax nn SOURCE MISSION TIMER NUMBER, 1 to 60 + Specifies ADD to "base time" - Specifies SUBTRACT from "base time" ddd The number of DAYS to add/subtract to "base time" / Separates DAYS from TIME hh The number of HOURS to add/subtract to "base time" mm The number of MINUTES to add/subtract to "base time" ss The number of SECONDS to add/subtract to "base time" : Separates hours:minutes and minutes:seconds Note that the days portion of the command, "ddd/", may be omitted if the value is zero; omitting the days is equivalent to a days portion of "000/". The number of digits shown for each portion of the command may not be exceeded, but leading zeroes may be omitted. Times may differ by as little as one second. (In fact, they may be identical if you wish.) As an example of relative Mission Timer programming, suppose that the "base time" for a sequence of events is on 7/11/1991 at 13:44:00 UTC and that a series of subsequent events will occur at this "base time" plus 37 seconds, 1 minute and 30 seconds, and 3 hours and 7 minutes. The following commands will set up this sequence of Mission Timers: 25 Event Timer Number Base Event Event Name 7/11/91 Event Date 13:44 Event Time 26 First Subsequent Timer Number #25+00:00:37 Relative time to Mission Timer 25 27 Second Subsequent Timer Number #25+00:01:30 Relative time to Mission Timer 25 28 Third Subsequent Timer Number #25+03:00:07 Relative time to Mission Timer 25 After these commands have been entered, Mission Timers 25 through 28 will contain the base event and the three subsequent events. Since the "copy" format has been used for the subsequent events, the names will be identical Program JPLCLOCK Multimission Control Center Clock Page 25 in all four Mission Timers. You may then edit Mission Timers 26 through 28 by selecting them in turn, entering a new event name, then pressing TAB in place of a date entry to leave that information unchanged. Future events are sometimes rescheduled. To accommodate this situation, the "#nn" command may be used to copy an event to the same Mission Timer with a positive or negative time adjustment. Select the Mission Timer number you wish to adjust, enter the "#nn" command as described above (including the relative time adjustment) and the change will be made. For example, to advance the time for Mission Timer 44 by one hour and thirty minutes, enter the following commands: 44 Timer Number to adjust #44+1:30 Advance the time by 1:30 This example illustrates a "shortcut": if the seconds are zero, they may be omitted. Similarly, if both minutes and seconds are zero, both may be omitted. The hours could also have been entered with a decimal fraction and the minutes omitted: "#44+1.5" to achieve the same result. The optional days ("#44+3/1:30" to advance the time by 3 days, 1 hour, 30 minutes) could have been used if required. If you wish to enter new data for this mission timer, type the new name for this Mission Timer followed by ENTER. You will then be asked to enter the new DATE for this timer: (ESC to CANCEL) Enter new DATE (MM/DD/YYYY or JD/MJD): Press ESC to CANCEL making changes to this Mission Timer or type the new DATE followed by ENTER. Dates are normally entered using "MM/DD/YYYY" format where "MM" is the MONTH (month number), "DD" is the DAY, and "YYYY" is the YEAR. JPLCLOCK will also accept a two-digit year and add 1900 to the value entered; "1991" and "91" will both be accepted as "1991". JPLCLOCK will also accept several "JD" (Julian Date) formats by prefixing the date entry with one of the following: Prefix Julian Date Format Name Starting Date ------------------------------------------------------------------- JD 2448424.375000 Standard Julian Date (-4713 JAN 1.5) MJD 48423.875000 Modified Julian Date (1858 NOV 17.0) DJD 33404.375000 Dublin Julian Date (1900 JAN 0.5) TJD 8423.875000 Truncated Julian Date (1968 MAY 23.0) All of the Julian Date formats in the example are equal to June 16, 1991, at 14:00 PDT. "JD" is the standard format used by astronomers and most scientists. The other formats have been developed to reduce the number of digits required to uniquely identify a specific date but have more restricted range if negative numbers or large numbers are to be avoided. NASA, for example, frequently uses the "TJD" format. NOTE: When one of the Julian Date formats is used, the time is implicit and the "New TIME" prompt will be skipped. Thus, an entry of "JD2448424.375" or "TJD8423.875" would yield the same time and date as "6/16/91" (for DATE) and "14:00P" (for TIME). After the new date has been entered (and provided you did not use one Program JPLCLOCK Multimission Control Center Clock Page 26 of the Julian Data formats), you will be prompted for the new TIME: (ESC to CANCEL) Enter new TIME (UTC or Zone): Type the desired new time using the "HH:MM:SS" format followed by ENTER. JPLCLOCK is very flexible as to the time format. JPLCLOCK requires the 24- hour format. Decimal fractions for the last value entered are accepted, leading zeroes are NOT required, the separator may be either the colon (":") or the comma (","), and the entry may omit values which are zero. Each of the following examples will be accepted as 14:15 (2:15 PM): 14:15:00 14,15 14.25 JPLCLOCK assumes that the time entered is Coordinated Universal Time (UTC) unless a suffix is added to indicate otherwise. The following time zone suffixes are supported by JPLCLOCK: U UTC Universal Coordinated Time A AST/ADT Atlantic Time Zone E EST/EDT Eastern Time Zone C CST/CDT Central Time Zone M MST/MDT Mountain Time Zone P PST/PDT Pacific Time Zone Y YST/YDT Yukon Time Zone (sometimes "Alaska") H HST/HDT Hawaiian Time Zone Except for UTC, JPLCLOCK will automatically adjust the entered time for the appropriate time zone AND for daylight savings time (if in effect). Thus, an entry of "14:00P" will be interpreted as Pacific Standard Time (PST) if the Daylight Flag is OFF, and as Pacific Daylight Time (PDT) if the Daylight Flag is ON. If no suffix is included or if the "U" suffix is added, no adjustment for the Daylight Flag will be made and the time entry will be accepted as UTC. By using the appropriate time zone suffix, times may thus be entered directly in local time for each time zone in the United States, Alaska, and Hawaii without making any conversions (or mistakes!). JPLCLOCK makes the required conversions to the time (and date, if necessary) and displays the resulting Mission Timer values in UTC. Program JPLCLOCK Multimission Control Center Clock Page 27 Set SELECTED EVENTS ------------------- Press F2 to set the SELECTED EVENTS. The program will display the currently selected SELECTED EVENTS, if any, and remind you that the SELECTED EVENTS are displayed ONLY when the SMALL Main Clock window is active. To make the SMALL Main Clock window active, press ALT-F6 when the Main Clock window is on the screen. SELECTED EVENTS are active with SMALL Main Window ONLY! # MT# Mission/Event Name ---------------------------------------- 1 11 Hubble Space Telescope 2 17 Gamma Ray Observatory 3 23 Voyager 1 4 24 Voyager 2 (ENTER to CLEAR, TAB to SKIP, ESC to CANCEL) Enter MISSION/EVENT TIMER # for Selected Event #1: In the sample display above, the column marked "#" lists the four SELECTED EVENT timers in order; tThe column marked "MT#" lists the Mission/Event Timer which is associated with the corresponding SELECTED EVENT; and, the column marked "Mission/Event Name" lists the name of the selected Mission/Event Timer. The information for each SELECTED EVENT is requested in turn. The first prompt asks for Selected Event #1. As noted, press ENTER to clear that event, press TAB to skip to the next event, or press ESC to cancel and return to the Main Menu. The only information that can be entered here is the Mission/Event Timer number which you wish to be associated with each SELECTED EVENT. The actual data, the event name, date, and time, must already have been entered into the Mission/Event Timer (F3+F1 from the Main Menu). Note also that the while the full Mission/Event Name is displayed on the menu as shown above, the actual window on the screen will truncate the name to a maximum of 19 characters; this is because the SELECTED EVENT windows are somewhat narrower than the main Mission/Event Timer windows. If you wish to edit the name so that it will fit correctly in the SELECTED EVENT windows, you must edit the Mission/Event Timer entry using F3+F1 from the Main Menu (or just F1 from the event menu). Program JPLCLOCK Multimission Control Center Clock Page 28 F4 Set DAYLIGHT and Defaults ------------------------------ Function Key F4 allows you to switch the system from local STANDARD time to local DAYLIGHT time and set a number of program defaults. Pressing F4 from the Main Menu displays the following menu: Enter selection: F1 Switch STANDARD/DAYLIGHT Time F2 Set LOCAL NAME and TIME ZONE F3 Restore Program DEFAULT DATA F4 Set PAGE and TEXT Mode Delays, 15 30 ESC Return to Main Menu ENTER Resume Program JPLCLOCK Enter selection: Pressing ESC will return you to the Main Menu. Pressing ENTER will resume operation of program JPLCLOCK. Pressing F1 will switch the Daylight Flag between Standard time and Daylight time. NOTE: This function does NOT change your computer's clock; you must set the correct local time BEFORE using this function! Pressing F2 will allow you to enter a new name for your location and to set its standard UTC Offset (in hours) and Daylight Flag. Pressing F3 will restore the "hard-coded" program default data for the Local Name, Location Clocks and Mission Timers. Pressing F4 will prompt you to enter new values for the PAGE delay and the TEXT delay. The current values are shown at the right. The following information will be displayed and you will be asked for the PAGE Delay: PAGE Delay sets the time to display each page of Mission Timers. TEXT delay set the time to display each text page. PAGE Delay must be between 5 and 900 seconds. TEXT Delay must be between 5 and 900 seconds AND an even multiple of PAGE Delay. The times are adjusted if necessary. Enter PAGE Delay [15] (seconds): The current PAGE Delay is shown in square brackets. Enter the desired new value for the PAGE Delay in seconds or press ENTER to leave the present value unchanged. You will then be asked for the TEXT Delay: Enter TEXT Delay [30] (seconds): The current TEXT Delay is shown in square brackets. Enter the desired new value for the TEXT Delay in seconds or press ENTER to leave the present value unchanged. Note the minimum and maximum values allowed for these delays, 5 and 900 seconds respectively. Note also that the TEXT Delay must be an even multiple of the PAGE Delay (for internal programming reasons). If this is not the case, TEXT Delay will be automatically adjusted accordingly. I recommend the values shown in the examples above as the minimum values for JPLCLOCK. Smaller values allow insufficient time for reading. Program JPLCLOCK Multimission Control Center Clock Page 29 F5 Read or Save INI Files --------------------------- JPLCLOCK reads the file JPLCLOCK.INI each time it is started, and writes a new JPLCLOCK.INI file each time the program is halted. This INI file contains all the information about the local installation, the Location Clocks, and the Mission Timers. For installations where only the first six Mission Timers are used, this information will change only infrequently and additional INI files will probably not be required. Users may find it convenient to re-read the normal INI file, JPLCLOCK.INI, if they have incorrectly changed information and wish to restore the original information. (NOTE: Exiting program JPLCLOCK in this situation will cause the incorrect information to be written to file JPLCLOCK.INI and the original data in that file will be permanently lost!) As a protection against this sort of problem, it is recommended that all users create a standard INI file, named STANDARD.INI for example, that represents the normal program configuration. Function Key F1 may then be used from this menu to reload that normal configuration at any time. However, installations using JPLCLOCK in the PAGE mode may find that advance preparation of INI files (using another computer running JPLCLOCK) is very helpful in preparing for upcoming events on multiple missions. In order to facilitate this process, JPLCLOCK can both read and write INI files. This takes advantage of JPLCLOCK's internal editing capabilities (using Function Key F3 from the Main Menu) and may avoid errors due to manual editing and time/date conversions. A new set of Mission Timers can be prepared on the "offline computer", tested, and written to an INI file for use on the "online computer". Files may be exchanged either via disk or via local area networks. Once the new INI file has been loaded onto the "online computer", JPLCLOCK may be paused, the new INI file read, and program operation resumed. Performed in this manner, the entire updating process will take the "online computer" offline for a few seconds. Any number of INI files may be prepared in this fashion, the only requirement being that they have unique names. INI files MUST have the file type ".INI". The filename may be any legal file name EXCEPT "JPLCLOCK.INI". Manual editing of INI files is NOT recommended; however, if this is done be certain to use a simple ASCII editor or an editor which has a "non-document" mode. Although the format of the INI file uses a simple comma-delimited format, an error in the file structure may cause the program to operate incorrectly or to crash (halt with an error message). If all else fails, delete the file JPLCLOCK.INI and restart the program; JPLCLOCK will then use its internal default data and construct a new INI file. Pressing Function Key F5 from the Main Menu will display the following menu: F1 Read external INI File F2 Save external INI File ESC Return to Main Menu ENTER Resume program JPLCLOCK Enter selection: Press F1 to read an INI file or F2 to write an INI file. All files are assumed to be in the current drive and directory. For file read operations, the file must exist. For file write operations, if the file does not exist Program JPLCLOCK Multimission Control Center Clock Page 30 it will be created and if the file does exist it will be overwritten. If either F1 or F2 is pressed, the following prompt will be displayed: INI files contain the setup and mission/clock data for JPLCLOCK. Enter the name of the INI file which you wish to read or write. Do NOT include a filetype; the program automatically adds '.INI'. Enter filename (without .INI): Press ESC to CANCEL the file read or write. Press ENTER to use the default file name JPLCLOCK.INI. Otherwise, type the filename WITHOUT the ".INI" filetype followed by ENTER. JPLCLOCK will automatically append ".INI" to the filename and then read or write the file and return to this files menu. INI Files from Other Locations ------------------------------ Except when JPLCLOCK is first started, the information specific to your location (Location Name, UTC Offset, Daylight Flag, etc.) is NOT processed when you read an INI file using F5. Therefore, if you receive an INI file from elsewhere, you should rename it to a convenient name (which might remind you of the source of the data, for example) and then read it into JPLCLOCK using F5. Since all of the remaining information in the INI file is recorded using UTC, JPLCLOCK will be able to make the necessary time conversions for display in your time zone. If you wish to use missions or events from a received INI file, you may read it in using F5, then view (and record or capture from the screen) the information in each Mission Timer Page. Having recorded the information, you may then re-read your own JPLCLOCK.INI file (press ENTER when asked for the INI filename) and enter the mission or event data you recorded using F3 as usual. Note that the times and dates shown on each Mission Timer page are always Coordinated Universal Time (UTC), not your local time, so do not include a time zone suffix when entering the time recorded from another INI file! Editing INI Files ----------------- Although it is not recommended for the novice computer user, the Mission Timer information contained in an INI file may be edited or copied from one file to another. Before editing INI files, make a backup copy of your JPLCLOCK.INI file using another name such as "BACKUP.INI". This will preserve your JPLCLOCK.INI file in the event you make a mistake. Use only a simple ASCII editor, or use a word processor program in the "non-document" or "ASCII" mode! The last 60 lines of the INI file contain the information for Mission Timers #1 through #60. A typical line appears as: "Mission Name",2448135.30419 The words within the quotation marks ("Mission Name") are the name of the mission or event, followed by a comma, and the number is the Julian Date for the mission or event time. An unused Mission Timer is shown as: Program JPLCLOCK Multimission Control Center Clock Page 31 "",0 This is known as the "comma delimited format", used by BASIC and other software for file data. No error checking is performed, so observe the file structure and format exactly! Errors in the INI file structure, especially in the initial several lines, can cause JPLCLOCK to crash (exit with an error message); if all else fails, erase the bad file and start over with a fresh INI file copied from the file JPLCLOCK.INI as written by JPLCLOCK. By editing an INI file, events from other locations or sources may be "spliced" into your own INI file. For example, if you receive an INI file which includes a number of events of interest, use your editor to snip out the Mission Timer lines you want and then replace a corresponding number of lines in a copy of your JPLCLOCK.INI file with the new lines. I recommend placing the new lines at the END of the file; you may use F3 from the Main Menu to copy them to the desired Mission Timer once you read in the edited file. Do NOT edit file JPLCLOCK.INI; always make a copy with a new name and read it using F5. This will preserve your data in case your make an error! Program JPLCLOCK Multimission Control Center Clock Page 32 F6 Self-Calibration using TIMESET ----------------------------------- Function Key F6 enables a special self-calibration procedure which causes JPLCLOCK to use program TIMESET to perform a series of calibration measurements over a period of 7 hours. Note that TIMESET must have been correctly configured and tested prior to automatic use. See the procedure for configuring TIMESET in the section F10 TIME SYNCHRONIZATION below and read the TIMESET documentation. When the Self-Calibration procedure is initiated, JPLCLOCK immediately makes a call using TIMESET and resets the drift and offset parameters. The program then makes subsequent calls at 1, 2, and 4 hour intervals (for a total of four calls) to enable calculation of new parameters. When the last call has been completed, a reasonable calibration of the DOS clock should have been calculated. The computer must be allowed to run JPLCLOCK continuously, with the clocks displayed, during the procedure. However, the usual commands are available for use between calls PROVIDED you do not exit to DOS and the clocks are displayed when the time comes to make each call. Of particular interest after the second call (in other words, after more than one hour has elapsed since the procedure was started) is the calculated DOS Clock Drift. With the main clock display on the screen, press ENTER twice to obtain the Main Menu, then press F10+F1 to view the current data: DOS time: 06:45:26.17 07-05-1991 CMOS time: 06:45:27 07-05-1991 JPLCLOCK time: 06:45:27 PDT 13:45:27 UTC JPLCLOCK date: 07/05/1991 07/05/1991 JPLCLOCK will start automatically in 88 seconds Current Julian Date: 2448443.073229 Last Synchronized: 2448442.500926 Time since Last Sync: 0.572303 days Current Clock Offset: 0.00 seconds Current DOS Drift Rate: -1.512899 seconds/day Current Total Adjust: -0.87 seconds Press ESC for Sync Menu, ENTER to ADJUST data: In the example above, about half a day has elapsed since the last synchronization was performed. As a result of that measurement, JPLCLOCK has calculated that the drift rate of the DOS clock is -1.512889 seconds per day and that the current time must be adjusted by SUBTRACTING -0.87 seconds from the DOS clock. Above these data are four time displays showing the present DOS clock (the one being calibrated), the CMOS clock (the computer's hardware clock), and the JPLCLOCK time and date both for the local time zone and for UTC. The JPLCLOCK time is the time displayed in the Main Clock window and reflects the current calculated adjustment from the DOS time. When using self-calibration, ALWAYS press ESC after viewing these data to return to normal operation. If you press ENTER by mistake, press the TAB key to leave all items unchanged. JPLCLOCK generates a "temporary" automatic synchronization schedule during self-calibration, saving the prior schedule (if any). Thus, the Program JPLCLOCK Multimission Control Center Clock Page 33 program will perform the procedure over 7 hours and then revert to the original automatic schedule (if automatic synchronization is ENABLED) or turn off automatic synchronization (if automatic synchronization is DISABLED). You may verify the current status of the automatic synchronization from the Main Menu by pressing F10+F3; this will show the schedule now in effect; note that the times shown in the schedule are UTC. F1 Execute TIMESET (Manual) F3 Set Automatic Synchronization: ENABLED NEXT TIME = 00:55:00 UTC START = 08:55:00 UTC INTERVAL = 04:00:00 ESC Return to Sync Menu ENTER Resume Program JPLCLOCK Enter selection: In the example shown, the automatic synchronization schedule has been set to start at 00:55:00 UTC and repeat every four hours. Comparing this schedule against the current time, JPLCLOCK will next perform the synchronization at 08:55:00 UTC. Program JPLCLOCK Multimission Control Center Clock Page 34 F7 Switch TEXT Mode --------------------- Function Key F7 permits you to enable or disable the TEXT mode provided the text file JPLCLOCK.MSG is present on the current drive and directory when the program is started. This command is equivalent to the "/TEXT" command line option. If the file JPLCLOCK.MSG has been added while using the DOS SHELL (F9), the text will NOT be available since the file is read ONLY when JPLCLOCK is started from DOS. Quit program JPLCLOCK and restart the program if you wish to add or edit JPLCLOCK.MSG. F8 Switch PAGE Mode --------------------- Function Key F8 permits you to enable or disable the PAGE mode. This command is equivalent to the "/PAGE" command line option. Disabling the PAGE mode will also disable the TEXT mode if it is currently enabled. F9 DOS Shell (DOS 3.3+ ONLY) ------------------------------ Function Key F9 invokes the DOS SHELL, loading a second copy of COMMAND.COM and displaying the usual DOS prompt. Most DOS commands and programs are now available. To return to JPLCLOCK, type the following at the DOS prompt (followed by ENTER): EXIT Note that using the SHELL with versions of DOS prior to Version 3.3 may yield unpredictable results. Because program JPLCLOCK remains in memory and a second copy of COMMAND.COM is also loaded into memory, the memory available to execute programs under the SHELL is considerably reduced. Some programs may fail to execute due to insufficient memory or you may receive an "Out of Memory" message. If this happens, check to see that all TSR (Terminate and Stay Resident) programs that are not required have been disabled. If this does not solve the problem, the program in question cannot be executed with the shell. Except for the potential memory problem, the SHELL operates exactly the same as normal DOS. Although JPLCLOCK is resident in memory, it is not active. The timer which causes execution of the program to automatically resume after some seconds is therefore also NOT active and the computer will remain in the SHELL until you type "EXIT" followed by ENTER. Program JPLCLOCK Multimission Control Center Clock Page 35 TIME SYNCHRONIZATION -------------------- As discussed at length elsewhere, the hardware and software clocks on the typical personal computer do not keep accurate time. In order to use JPLCLOCK in a critical installation such as the JPL Multimission Computer Control Center, additional steps must be taken to ensure the accuracy of the JPLCLOCK display. NOTE: Before proceeding with this section, please read the section DOS CLOCK CALIBRATION below. An understanding of that section and its procedures is essential before time synchronization is attempted. Time synchronization may be accomplished either manually (using the DOS TIME command outside program JPLCLOCK) or by using the program TIMESET. TIMESET, in turn, may be invoked either on demand or its use may be scheduled to occur at any desired interval. The balance of this section is concerned with the use of program TIMESET. TIMESET is copyrighted software distributed separately, and it must be registered before regular use. See the TIMESET documentation for details. (Additional information on TIMESET is also given in the section DOS CLOCK CALIBRATION, below.) Configuring Program TIMESET --------------------------- Before program TIMESET may be used with JPLCLOCK it must be configured for your computer system. In addition to the "regular" configuration described in the TIMESET documentation, an additional process is required here. In order for TIMESET to operate successfully with JPLCLOCK, two special version of the program must be prepared: one for your local STANDARD time and one for your local DAYLIGHT time. If you have not already done so, configure TIMESET by entering the following command at the DOS prompt: TIMESET /C The following configuration screen will be displayed for your approval. The information shown here is that used on one of my test computers. Outside phone: NULL Naval Observatory: 12026530351 Inst. Stds. Technol.: 13034944774 ===> Time zone: PACIFIC ===> Time season: STANDARD Serial port: COM1 Dialing method: TONE Dialing baud rate: 2400 Lock modem speed: NO User's commands: L2X4S7=45&C1&D2 Program JPLCLOCK Multimission Control Center Clock Page 36 Computer clock: DOS CLOCK-CALENDAR ===> Immediate/countdown: IMMEDIATE ===> Manual/automatic: AUTO NIST Video type: COLOR You will not need to change some of the information shown here. Verify that the modem information is correct. You WILL need to set your TIME ZONE to the correct zone and to set the TIME SEASON to STANDARD. Make sure the IMMEDIATE/COUNTDOWN is set to IMMEDIATE and that MANUAL/AUTOMATIC is set to AUTO NIST or AUTO USNO (depending upon the time service you wish to use. The four critical items are each marked with an arrow ("===>") in the sample above. Once all data are correct, press F10 to save the configured version. You will now have a program file, TIMESET.COM which represents your basic TIMESET configuration for STANDARD time in your time zone. It may be used at any time by simply entering the following command at the DOS prompt: TIMESET Use the DOS COPY command to save a separate STANDARD TIME version of this program for JPLCLOCK's use: COPY/B TIMESET.COM TIMESTD.COM Now, repeat the configuration process by entering the command "TIMESET /C" and leave everything the same EXCEPT change the TIME SEASON to DAYLIGHT. Press F10 when you have made the change to save a DAYLIGHT version of TIMESET. Then use the DOS COPY command to save a separate DAYLIGHT TIME version of this program for JPLCLOCK's use: COPY/B TIMESET.COM TIMEDAY.COM Use the DOS DIR command to be certain that you now have two specially named versions of TIMESET on disk: TIMESTD.COM TIMEDAY.COM Copy these two files to your JPLCLOCK disk and/or directory. IMPORTANT NOTE -------------- Unfortunately, TIMESET cannot be instructed to select STANDARD TIME or DAYLIGHT TIME from the command line, only by changing the its configuration. JPLCLOCK already knows which time season is in effect and uses these two special versions of TIMESET as appropriate. If these two files are not present, JPLCLOCK's auto- matic time synchronization functions will NOT execute correctly! Program JPLCLOCK Multimission Control Center Clock Page 37 CHECK AGAIN TO BE SURE THESE TWO FILES ARE IN YOUR JPLCLOCK DRIVE AND DIRECTORY: TIMESTD.COM TIMEDAY.COM TEST BOTH PROGRAMS CAREFULLY TO BE CERTAIN THAT EACH VERSION CALLS THE SELECTED TELEPHONE TIME SERVICE AND SETS YOUR COMPUTER CLOCK CORRECTLY AND FOR THE SELECTED TIME SEASON. JPLCLOCK HAS NO WAY OF DETECTING IF YOUR COMPUTER CLOCKS ARE SET INCORRECTLY! This completes configuration of program TIMESET for use with JPLCLOCK. It might be wise to make backup copies of the two special versions of the program so that they will be readily available if needed. Time Synchronization Menu ------------------------- F1 VIEW or SET Time Sync Data F3 TIMESET Time Synchronization ESC Return to Main Menu ENTER Resume Program JPLCLOCK Enter selection: Select F1 to view the current time synchronization data or to manually execute program TIMESET. Select F3 to enable or disable automatic time synchronization using program TIMESET. VIEW or SET Time Sync Data -------------------------- Current Julian Date: 2448430.351713 Last Synchronized: 2448428.036412 Time since Last Sync: 2.315301 days Current Clock Offset: 0.00 seconds Current DOS Drift Rate: -3.034839 seconds/day Current Total Adjust: -7.03 seconds Press ESC for Sync Menu, ENTER to ADJUST data: Press ESC to return to the Time Synchronization Menu, or press ENTER to adjust the Last Synchronized, Clock Offset, and/or DOS Drift Rate parameters. See the section DOS CLOCK CALIBRATION for additional information on measuring these parameters. During CALIBRATION or after the DOS software clock has been correctly set, do NOT manually adjust these data! Program JPLCLOCK Multimission Control Center Clock Page 38 TIMESET Time Synchronization ---------------------------- F1 Execute TIMESET (Manual) F3 Set Automatic Synchronization: ENABLED NEXT TIME = 20:55:00 UTC START = 00:55:00 UTC INTERVAL = 04:00:00 ESC Return to Sync Menu ENTER Resume Program JPLCLOCK Enter selection: Press F1 to immediately execute program TIMESET. JPLCLOCK will select either program TIMESTD or TIMEDAY depending on whether it is set for STANDARD or DAYLIGHT time. Press F3 to enable, disable, or change the automatic time synchronization function. The sample shown above indicates that the automatic function is ENABLED, that it will next occur at 20:55:00 UTC, and that JPLCLOCK will automatically schedule time setting starting at 00:55:00 UTC each day and at four hour intervals thereafter. Press ENTER to DISABLE the automatic time synchronization feature, or enter the START time and the TIME INTERVAL when requested. As a general rule and to minimize use of the NIST and USNO telephone time services, the longer the synchronizing interval, the better accuracy is obtained. This is because the DOS clock ticks occur at 55 millisecond intervals and in order to maintain the desired accuracy of plus or minus 250 milliseconds per day or better, we must make this "granularity" small compared to the total time used to make the measurements. Where practical, I recommend a normal interval of at least 8 hours and preferably 12 or more. Program JPLCLOCK Multimission Control Center Clock Page 39 DOS CLOCK CALIBRATION --------------------- The primary purpose of JPLCLOCK is to display the current time and other related information in the JPL Multimission Computer Control Center. Accuracy and precision in that environment are essential. There is a tendency these days to accept whatever a computer says as the absolute truth without regard for whether or not the information is even "reasonable". For something as basic as time, even an experienced computer user often assumes that it is correct. JPLCLOCK attempts to match reality with that expectation. Given that a computer clock has been set with reasonable accuracy, the computer's time will indeed be sufficient for many applications; if you are using a word processing or spreadsheet program, knowing the time to within a minute or two is probably adequate. For JPLCLOCK, however, this level of accuracy simply will not suffice; when used in the Mission Control Center, the information displayed must be correct to within a second. Unless other steps are taken to set the clock and to maintain its accuracy, this will not be the case. No matter how accurately the clock on a typical personal computer is set, it will only be a matter of hours before the time will have drifted by some seconds. Measured over a number of days, the accumulated errors can easily amount to several minutes. The timekeeping operations of an IBM-compatible computer are actually performed by two separate and independent functions: a clock-calendar integrated circuit and lithium battery combination which maintains the current time and date in hardware; and a section of the MS-DOS or PC-DOS operating system software which maintains the current time and date in software. When computer power is off, the hardware chip continues to operate using its battery; when the computer is started ("booted"), the operating system software reads the hardware clock and sets its internal software clock. Absent special software, the DOS time relies entirely on the software clock until the next time the computer is restarted. Unfortunately, neither of these clocks was designed for accuracy; early versions of the PC did not even include the hardware/battery arrangement. Even the typical electric clock, which uses the power line frequency for its timekeeping reference, is far more accurate. The accuracy of the DOS time at any instant is the result of the accumulated errors in both clocks. The hardware clock will drift as a function of time, temperature, and crystal aging; the software clock will gain or lose time depending upon the skill with which its software was written and how well that software "cooperates" with the balance of the computer's hardware and software. Some software, especially network and high speed communications software, can prevent the DOS clock software from incrementing when it should, usually resulting in the DOS clock losing time. The problem was compounded with the release of DOS Version 3.3; beginning with that version, the DOS TIME and DATE commands adjust BOTH the hardware and software clocks and thereby potentially eliminate the hardware clock as even a modestly reliable reference. If today's personal computers used the power line frequency as their primary reference, and only used the battery powered crystal oscillator if the power line was not present, clock accuracy could at one stroke be improved by at least several orders of magnitude. Program JPLCLOCK Multimission Control Center Clock Page 40 Setting DOS Time ---------------- Bearing these considerations in mind, there are a number of approaches to the DOS time question. The most obvious approach, used by the vast majority of computer users, is to either ignore the computer clock entirely or to say "It's close enough". Regardless of the application, I strongly recommend that the DOS clock be set to the approximate time if only to assure that files are more or less correctly date stamped. If the accuracy of DOS time is important, the computer clock may be set or synchronized in a number of ways, some of which are described below. In this context, "ACCURACY" means the accuracy of the time setting operation and NOT the longer term accuracy of the DOS time. 1. TELEPHONE: Many local telephone companies offer a telephone time service, usually with a message such as "When you hear the signal the time will be ... (beep)". I am not aware of any commercial equipment which uses this signal for time setting purposes. ACCURACY: Generally plus or minus 5 seconds. With the advent of digital voice response equipment, the accuracy has improved in recent years to perhaps plus or minus 1 second. 2. COMMERCIAL RADIO: Use commercial radio hourly time signals to manually set the time. (My experience suggests that the CBS time signal is normally quite reliable.) ACCURACY: Usually within plus or minus 2 seconds, depending upon the source. 3. SHORTWAVE RADIO: Time signals are broadcast on shortwave radio stations WWV and WWVH by the National Institute of Standards and Technology. These time signals may be used to manually set the time. WWV and WWVH broadcast on several frequencies: 2.5MHz, 5MHz, 10MHz, 15MHz, and 20 MHz (WWV only). Reception will vary according to your distance from the transmitter, time of day, and atmospheric conditions. These time signals are very precise; the only major variable is the transmission time. Outside North America, other national radio services such as the British Broadcasting Company's BBC World Service offer accurate hourly shortwave time signals. ACCURACY: Time setting using WWV or WWVH can usually be performed to within about plus or minus 250 milliseconds, of which up to 25 milliseconds is transmission time and the balance is user response time. With practice, plus or minus about 100 milliseconds is practical. 4. NIST/USNO TELEPHONE TIME SERVICE: When real precision and accuracy are required, the computer clock may be set remotely using the telephone time service of either the National Institute of Standards and Technology (NIST, formerly the National Bureau of Standards or NBS) in Boulder, Colorado or Hilo, Hawaii, or the U.S. Naval Observatory (USNO) in Washington, D.C. This method requires a modem connected to a telephone line and is available Program JPLCLOCK Multimission Control Center Clock Page 41 for systems using DOS version 3.3 or higher AND equipped with 80286 processor or higher; some 8088-equipped systems may also use this method depending upon the type of clock hardware installed and the version of DOS being used. The recommended method uses the program TIMESET (see below) although other similar commercial and shareware programs are available. ACCURACY: This is the most accurate method available for setting the DOS clocks. Depending upon which service is used, NIST or USNO, and whether or not line delay compensation ("lag") is employed, the DOS time can be set to within plus or minus 2 milliseconds. However, since the "time ticks" of the DOS software clock occur every 55 milliseconds, or 18.2 times per second, this "granularity" effectively limits the accuracy of reading the DOS clocks. See the documentation for program TIMESET for additional discussion. 5. HEATH GC-1000 MOST ACCURATE CLOCK: The GC-1000 is a combination digital clock and scanning shortwave radio receiver which may be equipped with an RS-232 communications port for use with computers and other electronic equipment. This is the only method which provides more or less continuous accurate time information. RECOMMENDED! ACCURACY: When properly configured for your location, equipped with an external antenna, used with appropriate computer software, and when the receiver is locked to one of the WWV (or WWVH) time signals, the GC-1000 can provide time information and a standard calibration frequency to an accuracy of plus or minus 10 milliseconds. When signal lock is lost, the receiver scans the 5MHz, 10MHZ, and 15MHz broadcasts to reacquire signal and lock. Even after signal lock is lost, the receiver maintains an accuracy of plus or minus 100 milliseconds for some hours. Choose one of the methods suggested or a suitable alternative based upon your precision and accuracy requirements. Other methods of maintaining an accurate time standard, such an atomic clocks and NIST time code equipment, are available -- for a price. Those methods are beyond the scope of program JPLCLOCK and this documentation. Maintaining DOS Time -------------------- Just in case you missed the point earlier, accurately setting DOS time is only half the battle. Even if the DOS time is set very precisely as discussed above, all that assures is that the time is correct to the required accuracy at that instant. The problem then becomes one of knowing how the DOS clocks change or drift with time and how to compensate for those changes or, alternatively, checking the DOS time frequently enough that any drift on the part of the DOS clocks is acceptable for the intended application. Of the two clocks in a typical personal computer, the hardware clock is considerably more consistent and reliable. I have checked perhaps a dozen PC hardware clocks in recent years, and almost all kept reasonably Program JPLCLOCK Multimission Control Center Clock Page 42 good time over a period of several days; as expected, none kept "perfect" time. Typical drift rates ranged from about 3 seconds per day to near zero seconds per day, with the magnitude and direction of the drift more or less constant over the period of measurement. Once a hardware clock has been calibrated, therefore, the drift can be calculated with reasonable accuracy over periods of some weeks or more. For best results, the computer should always be left on and the ambient temperature held constant. Crystal aging rates suggest that calibration should be performed at least annually. The hardware clock is normally interrogated only when the computer is first started or rebooted. The correct time can therefore only be predicted at that moment for a calibrated hardware clock and given the last time that clock was synchronized with an appropriate time standard. Microsoft provides no standard software tools for interrogating the hardware clock at other times. Quite the contrary; beginning with DOS Version 3.3, using the DOS TIME and DATE commands to set the DOS software will also set the hardware clock and effectively destroy its usefulness as a calibrated time reference. I am at a complete loss to understand the reasoning behind this change in DOS; I presume that users were being "confused" by differences between the hardware and software clocks; instead of either explaining or fixing the problem, Microsoft elected to "legislate" the problem away -- a process any politician would recognize instantly. The only mitigating consideration is that any really effective solution would probably require hardware as well as software changes. Blame IBM, I guess. The software clock provides the only time information accessible to DOS using standard software. Since this clock is maintained entirely in software, with no reference to the hardware clock except at bootup, it is at the mercy of other software which may execute from time to time. The software clock increments its time using "interrupts", a technique which stops a software process in progress just long enough to do the required tasks and then resumes the interrupted process. These interrupts occur every 55 milliseconds. So long as none is missed, the software clock should keep accurate time -- if the software is written correctly and if the computer's crystal controlled oscillator is in turn accurate. It may be that neither of these conditions is true; certainly the crystal controlled oscillator (quite similar to the one which runs the hardware clock) was not designed for accuracy or stability. It's original purpose was solely to generate the necessary timing signals for the correct operation of the computer. Cost, not keeping accurate time, was the primary consideration in its design. Other software designers have contributed to the problem by writing software which, deliberately or inadvertently, prevents the software clock from being updated. Off-brand BIOS firmware can present occasional problems. Local Area Network (LAN) and high speed communications software are typical culprits in this respect. For example, a casual check of the clock while using Brooklyn Bridge (a computer-to-computer transfer program) indicated that the clock was effectively suspended when data transfers were in progress. In one relatively brief period, the DOS clock lost about 30 seconds. As a result of all of these factors, the accuracy of the DOS software clock can vary wildly from one computer to the next and from one manufacturer to another. One inexpensive "clone" computer that I'd rather forget couldn't manage to keep time to better than about 30 seconds per HOUR! Before planning to use a particular computer as a time reference with programs like JPLCLOCK, check the computer hardware and software you intend to use very carefully. Program JPLCLOCK Multimission Control Center Clock Page 43 Calibrating DOS Time -------------------- Regardless of the method used, the DOS time must be set from time to time in order to maintain even reasonable accuracy. More demanding applications will require calibration of the hardware or software clock or both. The method and frequency of calibration will depend upon your accuracy requirements and cost. For my "normal" work, involving program development and word processing, I use NIST station WWV and a digital PLL shortwave receiver to manually set my computer clocks on a regular basis. From time to time I require higher accuracy; given my location in California, I usually use a program like TIMESET to call the NIST Telephone Time Service in Boulder, Colorado when precise time setting is required. When using a program such as JPLCLOCK where consistent accuracy is essential over extended periods of time, calibration of the hardware and software clocks may be required. I recommend program TIMESET for this purpose. TIMESET is a copyrighted program by Peter Petrakis which is distributed using the "shareware" concept. If not available on a convenient bulletin board system, TIMESET may be obtained by writing: Life Sciences Software 8925 271st N.W., Suite 112 P.O. Box 1560 Stanwood, WA 98292 (206) 387-9788 US$35.00/copy (as of April, 1991) TIMESET is an elegant and very precise method for setting the hardware and software clocks in your computer. Note that TIMESET sets your computer based upon Coordinated Universal Time (UTC) rather than UT1; the offset between UTC and UT1 is displayed by TIMESET but is not used. TIMESET is superior to any of the several other similar programs I have evaluated. You must have a modem and a telephone line connected to your system to use TIMESET. Note that the process involves making a telephone call to either Boulder, CO or Washington, DC and toll or long distance charges may apply! For additional information on configuring TIMESET for use with JPLCLOCK, see the section TIME SYNCHRONIZATION. The current version of TIMESET, Version 6.0, is not without its shortcomings. First, if the modem does not make connection to a telephone line correctly, TIMESET may hang indefinitely waiting for a response from the modem which will never arrive. This is the case with one of my internal modems that is convinced that the first call after initialization is at 2400 baud; since the call to NIST is being made at 1200 baud, the modem is definitely "confused". This problem has not been observed when using a standard Hayes 2400 modem. Second, TIMESET does not record the statistical results of its operations to a disk file. This means that calibration must be performed manually; normal time setting, however, operates automatically with no problems. Third, TIMESET does not return an "error code" to indicate whether or not synchronization was successfully performed. I hope to convince Mr. Petrakis of the need to address these relatively minor problems in an otherwise excellent program. Program JPLCLOCK Multimission Control Center Clock Page 44 The method being used for time synchronization and adjustment will determine whether or not calibration of your hardware clock is required. If you use the Heath GC-1000 Most Accurate Clock, calibration is probably not required. Similarly, if you place a program like TIMESET in your AUTOEXEC.BAT file and synchronize your DOS clocks every time you start your computer, hardware calibration is not required. If, on the other hand, you wish to call NIST as infrequently as possible so as to minimize the telephone charges, hardware clock calibration is definitely recommended. Unless you use the Heath GC-1000 (or some other time standard) and poll it regularly, calibration of the software clock is always required. The following suggested calibration procedures assume the use of program TIMESET and that TIMESET has already been configured for your computer and for your time zone. See the TIMESET documentation for instructions. If you use some other program, it must provide similar information and you must make appropriate changes to these procedures as required by the software actually used. Program JPLCLOCK Multimission Control Center Clock Page 45 Manual Hardware Clock Calibration --------------------------------- Hardware clock calibration requires a minimum of 48 hours to accomplish. The computer should be located in the environment in which it is expected to operate and should be turned on and off at the "usual" times. The idea is to duplicate the actual operating conditions to the maximum extent possible, especially temperature. The following procedure is suggested: 1. Operate the computer in its normal environment and according to its usual schedule for at least 24 hours prior to the test. 2. Set the hardware clock using TIMESET according to instructions. Use a screen capture program or manually record the ACTION SUMMARY prepared by TIMESET. The most significant information is shown as: Local computer time was: 06:59:41.95 Set to: 06:59:44.01 Pacific Daylight Local computer date was: 06-19-1991 Set to: 06-19-1991, Wednesday 3. Operate the computer normally for the next 24 hours. Do NOT use the DOS DATE and TIME commands! 4. After approximately 24 hours, repeat the time setting with TIMESET and record the same information as in Step 2. 5. Using the data obtained in Steps 2 and 4, calculate the hardware clock drift in seconds per day. 6. Operate the computer normally for the next 24 hours. Do NOT use the DOS DATE and TIME commands! 7. After approximately 48 hours, repeat the time setting with TIMESET and record the same information as in Step 2. 8. Using the data obtained in Steps 4 and 7, again calculate the hardware clock drift in seconds per day. Repeat as required until consistent results are obtained. If consistent results cannot be obtained, the selected computer may not be suitable for your intended use. NOTE: The current version of JPLCLOCK does not directly use the hardware clock drift in its time adjustment calculations. This capability will be added in a future version. Instead, JPLCLOCK accepts a "Clock Offset" value which represents the total hardware clock drift in seconds between the last time synchronization was performed and the most recent time the computer was booted. If the computer is always synchronized immediately prior to running JPLCLOCK, the hardware calibration is not required and the Clock Offset should be set to zero. Program JPLCLOCK Multimission Control Center Clock Page 46 Manual Software Clock Calibration --------------------------------- Manual software clock calibration is quite similar to hardware clock calibration and is recommended for all installations using JPLCLOCK which do not plan to use the automatic synchronization and calibration features of the program. The recommended procedure requires 28 hours to accomplish. The computer should be located in the environment in which it is expected to operate and should be turned on and off at the "usual" times. The idea is to duplicate the actual operating conditions to the maximum extent possible, especially temperature. The following procedure is suggested: 1. Operate the computer in its normal environment and according to its usual schedule for at least 24 hours prior to the test. 2. Set the hardware and software clocks using TIMESET according to instructions. Use a screen capture program or manually record the ACTION SUMMARY prepared by TIMESET. The most significant information is shown as: Local computer time was: 06:59:41.95 Set to: 06:59:44.01 Pacific Daylight Local computer date was: 06-19-1991 Set to: 06-19-1991, Wednesday 3. Operate the computer normally for the next 4 hours. "Normal operation" means using the particular software, JPLCLOCK in this case, that is planned for the computer. Do NOT use the DOS DATE and TIME commands! 4. After 4 hours, repeat the time setting with TIMESET and record the same information as in Step 2. 5. Using the data obtained in Steps 2 and 4, calculate the software clock drift in seconds per day. 6. Operate the computer normally for the next 12 hours. "Normal operation" means using the particular software, JPLCLOCK in this case, that is planned for the computer. Do NOT use the DOS DATE and TIME commands! 7. After 12 hours, repeat the time setting with TIMESET and record the same information as in Step 2. 8. Using the data obtained in Step 7, again calculate the software clock drift in seconds per day. Repeat as required until consistent results are obtained. If consistent results cannot be obtained, the selected computer may not be suitable for your intended use. 9. Now enter the latest synchronization date and time (from Step 7) and calculated drift (from Step 8 or Step 5) in seconds per day into program JPLCLOCK. From the Main Menu, press F10+F1 and enter the data as prompted. Enter zero for Clock Offset. Program JPLCLOCK Multimission Control Center Clock Page 47 Other time sources may be similarly used to calibrate the DOS clock. The final result of this calibration should be a software clock drift in seconds per day that should remain reasonably stable for relatively long periods of time. The calculated clock drift is POSITIVE if your DOS clock GAINS time with respect to the time source and NEGATIVE if your DOS clock LOSES time with respect to the time source. These data may then be entered into JPLCLOCK so that the program will automatically adjust the displayed time for the predicted drift. Note that the predicted drift calculations assume that JPLCLOCK is operating continuously. If you exit JPLCLOCK and perform operations that affect the DOS clock (such as disk accesses or high speed communications), the drift calculations will still be accurate but you will have to add a clock offset to compensate for the DOS clock changes. If you turn off your computer, you must reset your clock (to the desired accuracy) and then adjust the last synchronization time to correspond to the time you reset your computer clocks. For maximum accuracy, perform a manual time synchronization (F10+F3+F1 from the Main Menu) each time you reboot your computer; JPLCLOCK will automatically update the last synchronization time. Program JPLCLOCK is a "well behaved" program written and compiled using Microsoft's QuickBASIC Compiler, Version 4.5. No "clever tricks" are used to fool the system into doing something that might interfere with accurate timekeeping by the DOS software clock. The software clock drift obtained by this suggested procedure should be relatively consistent from day to day. Program JPLCLOCK Multimission Control Center Clock Page 48 USING TEXT MODE --------------- In addition to its use in the Multimission Computer Control Center, JPL is also considering the use of JPLCLOCK as a means of displaying the current mission and event times in other locations at the Laboratory, and for display to visitors and guests. In order to explain the data, to provide additional commentary on missions in progress, and to provide other supplementary information, JPL suggested the addition of a TEXT mode to further enhance JPLCLOCK. Each time JPLCLOCK is started, it searches for a special message file named "JPLCLOCK.MSG" in the current drive and directory. If the file is found, it reads the file into memory and thereafter permits the TEXT MODE to be enabled. This occurs ONLY when the program is started from the DOS prompt; if you use the DOS SHELL (Function Key F9 from the Main Menu) to copy or create the special message file, JPLCLOCK will NOT recognize the file until the program is restarted. The TEXT mode has a capacity of up to 10 screen pages of text with 20 lines per screen page. The normal distribution of the program includes a demonstration message file with the name JPLCLOCK.MSG. To enable TEXT mode, you must first enable PAGE mode. This may be done when the program is started from the DOS prompt: JPLCLOCK /PAGE/TEXT or by using Function Key F8 (to enable PAGE mode) and then Function Key F7 (to enable TEXT mode) from the Main Menu. Disabling PAGE mode automatically disables the TEXT mode. TEXT mode cannot be enabled in the special message file JPLCLOCK.MSG was not found when the program was started OR if the file contains no text. When the TEXT mode is enabled, JPLCLOCK first cycles through all active Mission Timers (as in the usual PAGE mode), then cycles through all available text pages in order. The process then repeats. The sample special message file contains five text pages. When the TEXT mode is active and JPLCLOCK is cycling through all active Mission Timers and text pages, a special "bar meter" is displayed at the top left of the Mission Timer Windows. This is a row of ten special square symbols, one for each of the ten text pages, which indicates the status of the page. Each available text page is denoted by a BLUE symbol; the active text page symbol is flashing. Inactive text pages (pages without any text) are shown with a GRAY symbol. In addition to the prepared text in file JPLCLOCK.MSG, the display includes a title line with the program version number, the current Julian Date, and the local date in conventional notation. The second line displays the current UTC Time, Local Time, and the two "bar meters". The left bar meter gives the status of title pages, and the right meter the status of the Mission Timer pages. The following is the first screen page in the supplied sample file JPLCLOCK.MSG. Special "line drawing" characters actually used in the display have been replaced in this text by similar printing characters. Program JPLCLOCK Multimission Control Center Clock Page 49 | JPLCLOCK by David H. Ransom, Jr. Version 9126 | JD2448430.26897 22 JUN 1991 18:27:19 UTC 11:27:19 PDT ********** ********** ---------- NASA Jet Propulsion Laboratory ------------------------------------- Welcome to JPLCLOCK! -------------------- Written by David H. Ransom, Jr. Rancho Palos Verdes, CA JPLCLOCK is a real time clock and mission/event timer program written especially for the NASA Jet Propulsion Laboratory in Pasadena, California for use in the Multimission Computer Control Center (MCCC) and elsewhere in the Laboratory. The MCCC is the "nerve center" where all the NASA planetary missions such as Magellan, Ulysses, and Galileo are controlled. Other NASA and European Space Agency missions are also supported by the JPL MCCC either directly or through NASA's Deep Space Network, three large antenna systems located in Goldstone, California, near Madrid, Spain and near Canberra, Australia. The MCCC is in turn supported by the scientists and engineers at JPL and at the California Institute of Technology, which operates JPL for NASA. Preparing TEXT Files -------------------- The sample demonstration message file JPLCLOCK.MSG may be used as a template to create customized text files. When preparing text files for use with JPLCLOCK, use an ASCII editor, or use a word processor program in the "non-document" or "ASCII" mode. Before editing, make a backup copy of file JPLCLOCK.MSG. I recommend that all text files for JPLCLOCK be created with the filetype ".MSG". Future versions of JPLCLOCK may include a feature to read additional text files and the required filetype will be ".MSG". The sample file contains 5 screen pages of text. Each screen page consists of exactly 20 lines of text, and a maximum of 10 screen pages (or 200 text lines) is allowed. After creating a new text file (and having made a backup copy of the original JPLCLOCK.MSG file!), copy the new file to JPLCLOCK.MSG and start program JPLCLOCK in the TEXT mode to view the results. My testing indicates that it takes several attempts before the appearance of the screen pages suit my taste. The TEXT mode displays text lines exactly as it finds them in file JPLCLOCK.MSG. As illustrated in the sample file, the "line drawing" characters and other special characters are displayed. (Some editors are unable to place these special characters in a text file. I recommend the shareware editor QEDIT for editing text files for JPLCLOCK.) Program JPLCLOCK Multimission Control Center Clock Page 50 COMMENTS AND KNOWN PROBLEMS --------------------------- 1. Computer BIOS Problems Not all PC's are created equal. A program like JPLCLOCK may execute correctly on one machine and not on another. The most likely culprit in these cases is the computer's BIOS (Basic Input Output System) which is built into each machine (in ROM, Read Only Memory) by the manufacturer. Even computers with the same model number may have a different BIOS, depending upon when they were manufactured; different model numbers by the same manufacturer may perform differently. Brands which have demonstrated problems in this area include Tandy, Leading Edge, and Ergo. 2. Monitor Type and Video Adapter Cards Not all video adapter cards are created equal either. While most CGA adapters perform about the same, EGA and VGA adapters can vary considerably. The same card, operated in different video modes, can be a star or a lemon. There are too many different types of adapters to even attempt any generalizations. One practical note: Some VGA monochrome monitors "confuse" the VGA BIOS and/or the VGA adapter and require the command "MODE CO80" (from the DOS prompt) for proper gray-scale operation with JPLCLOCK. 3. Computer Processor and Math Coprocessor JPLCLOCK has been tested primarily on computers equipped with the 80286 or higher processor and including a math coprocessor chip. There are no known problems if the computer does NOT have a math coprocessor chip but there may be perceptible delays visible on the screen; obviously, there's no solution except a faster computer or the addition of a math coprocessor chip. No testing has been performed on 8088-class machines (the original PC and XT computers and their clones). Operations involving the CMOS clock/calendar chip will usually fail on these machines since their design did not include that feature; the various add-on clock chips and circuit cards are usually incompatible with the current clock chips. If you have such a computer and wish to use program TIMESET, read the TIMESET documentation carefully and test the program thoroughly before use with JPLCLOCK. 4. DOS Version and the Shell Feature The "Shell to DOS" feature, used by Function Key F9 from the Main Menu and when program TIMESET is executed from within JPLCLOCK, is generally NOT reliable for versions of DOS prior to 3.1 and the results of attempting to use this command with DOS Version 2.x and lower are unpredictable. I recommend MS-DOS/PC-DOS Version 3.3 as the best, most stable DOS available. The Shell feature may also fail on certain computers for no apparent reason, probably related to the BIOS. I have also performed limited testing on DOS Version 5.0 without any problems to date. (I'm still using a Beta Version of DOS 5.0 and will resume testing as soon as I get the Real Thing installed.) Program JPLCLOCK Multimission Control Center Clock Page 51 5. Unstable Hardware or Software Clocks Some clock circuits have been implemented in such a manner that they are essentially a simple tuned resistance-capacitance design which effectively ignores the presence of a crystal. Such circuits may drift wildly as a function of time, temperature and/or voltage, and make the host computer unsuitable for an application such as JPLCLOCK. Any decent crystal controlled oscillator should be able to hold to within a second per day, but not many PC computer clocks are that good. I've been told that tests on a typical PC hardware clock several years ago showed a 5% difference in clock frequency when operated on AC power versus the lithium battery. I would not have believed that big a difference was even possible with a crystal oscillator! However, what appears to be an unstable DOS clock may, in fact, be the fault of certain software. Network and communications software are notorious for turning off the interrupt system and doing other bad things which prevent the DOS clock from keeping accurate time. This problem usually shows up as a significant time loss AFTER network access or high speed communications. Avoid the use of these programs when running JPLCLOCK and eliminate any TSR (Terminate and Stay Resident) programs which may interfere with the clock. The fact that there are two clocks in the PC can cause confusion and apparent errors. While JPLCLOCK is running, only the DOS clock is interrogated and it is this clock that requires the most careful calibration for extended operations. However, each time a computer with a battery supported clock/calendar is booted, the hardware clock is used to initially set the DOS clock. These two clocks have independent drift direction and rate; thus, the time may appear to drift in one direction if the computer is booted frequently, and in the opposite direction if it is left on. Microsoft compounded the problem by "fixing" the DOS TIME command in Version 3.3 and up so that it sets both the hardware and software clocks, thereby eliminating the hardware clock as any sort of a reliable or stable reference! 6. Typical Calibration Results During the testing of JPLCLOCK I have used both 286 and 386 computers and have calibrated each of their software clocks using the NIST telephone time service. While the drift rates varied from computer to computer, each computer was able to maintain the correct time using JPLCLOCK to within 150 milliseconds after: a) running for a minimum of 4 hours prior to attempting calibration; and b) using a calibration time of at least 4 hours. Since the DOS clock ticks occur at 55 millisecond intervals, calibration runs of less than four hours will yield an uncertainty which is of the same order of magnitude as the desired calibration accuracy. For applications requiring maximum accuracy, these tests indicate that the computer should be set using NIST each time the computer is booted and then resynchronized at 4 to 24 hour intervals. The stability of the DOS clock will determine the optimum interval. JPLCLOCK records the measured drift rate each time it makes a synchronization call; use F3+F3+F1 from the Main Menu to view the data and adjust the synchronization interval to the longest time which yields consistent results. Another consideration is to minimize the number of calls to NIST or USNO; these telephone time services are a precious resource and should be used as infrequently as possible consistent with the needs of your application (as well as your willingness Program JPLCLOCK Multimission Control Center Clock Page 52 to pay the toll charges). 7. Color Variations Especially with EGA and VGA adapter cards, displayed colors may vary considerably from those described. The most common variation is "dim yellow" (used for the version number on JPLCLOCK's title screen) which often appears as either brown or a dim red which is all but indistinguishable from the "real" dim red. Other colors may also vary from system to system and from monitor to monitor. Program JPLCLOCK Multimission Control Center Clock Page 53 FUTURE IMPROVEMENTS AND FEATURES -------------------------------- JPLCLOCK is still a very young program and, in addition to repairing the inevitable bugs and problems that are bound to be found, I have a number of additional features that I hope to add in future releases of the program. Here are a few that are being considered: 1. Add better manual calibration procedures to include a brief tone so that users who don't choose to pay the telephone charges to NIST or USNO can still calibrate their systems reasonably accurately by using ratio stations WWV or WWVH. Casual experimentation on my part has indicated that I can hear differences as small as about 100 milliseconds without much difficulty. Propagation delay from Fort Collins, Colorado to the Los Angeles area is only about 20 milli- seconds so it should be simple to calibrate the clocks to plus or minus 250 milliseconds in a day or so. 2. Add automatic calibration of the hardware (CMOS) clock comparable to that now provided for the software (DOS) clock. This is a little more complicated since the hardware clock can only be read to the nearest second. 3. Add automatic synchronization using the Heath GC-1000 Most Accurate Clock. When equipped with an RS-232 interface and external antenna, the GC-1000 can maintain an accuracy of plus or minus about 10 milliseconds with WWV or WWVH. With software overhead, this probably translates into about plus or minus 50 milliseconds for the PC, the resolution of the DOS clock ticks. 4. Give the user the choice of displaying UTC or UT1 (required for navigation, for example) if synchronization is done using the NIST telephone time service or the Heath GC-1000 Clock (which are the only available services which supply the correction from UTC to UT1). The current correction is +0.2 seconds as of July 1, 1991. 5. For systems equipped with a CMOS clock/calendar chip (286 and higher), add the optional capability to use the hardware clock to adjust the DOS time when leaving JPLCLOCK to do disk operations, etc. 6. Add automatic correction to/from Daylight Savings Time. This will require automatically adjusting the DOS clock by one hour at the appropriate times each April and October. This is a real "must do"! 7. Improve readability of the times (especially when using the SMALL Main Window) by using an alternate font for EGA and VGA monitors. I'm at the mercy of QuickBASIC and the computer's BIOS for this feature; some systems accept alternate fonts from within a QuickBASIC program and others do not. Not all of these features may ever be added and others may find their way to the top of the list first. Comments and suggestions will be appreciated. Program JPLCLOCK Multimission Control Center Clock Page 54 UTC AND TIME ZONES ------------------ Coordinated Universal Time (UTC) is the world wide civil standard time as broadcast by national radio time services such as stations WWV and WWVH of the U.S. National Institute of Technology and Standards (formerly the National Bureau of Standards) and the BBC World Service. It is roughly the same as UT1, the time standard used by astronomers and scientists for celestial and solar system measurements. However, because the orbital time and rotation rate of the Earth is not constant, periodic adjustments of one second are required. These adjustments, called Leap Seconds, are usually made at the end of June and/or the end of December in order to maintain the difference between UTC and UT1 to within 0.9 seconds. As I discovered while writing my program ASTROCLK, there are many other defined time standards. Because of the ready availability of UTC for synchronization, JPLCLOCK assumes that the computer's internal clock is set to local time and that time has a fixed relationship to UTC. The original plan for time zones required each zone boundary to be located at the 15 degree meridians around the globe. Since that arrangement seldom coincided with national or political boundaries, many adjustments have been made over the past one hundred years for political reasons or for local convenience. Some time zones are approximately "nominal" while others are quite large; all of China, for example, uses a single national time zone -- at least officially. All civil time zones are related to UTC, usually by an integral number of hours (although there are several "half hour zones" and at least one "quarter hour zone"). Many countries, including the United States and most of Europe, also adjust their civil time by one hour during summer months. In the United States, Daylight time begins on the first Sunday in April and ends on the last Sunday in October. Other countries use different dates and those dates may change from time to time. JPLCLOCK can adjust for Daylight time for all time zones in the United States (including Alaska and Hawaii) with a single function key; other time zones must be individually set for standard or summer time. The following time zone abbreviations are used by JPLCLOCK for the main window and the four location clocks at the lower right of the display screen: UTC Coordinated Universal Time (formerly GMT = Greenwich Mean Time) AST Atlantic Standard Time ADT Atlantic Daylight Time EST Eastern Standard Time EDT Eastern Daylight Time CST Central Standard Time CDT Central Daylight Time MST Mountain Standard Time MDT Mountain Daylight Time PST Pacific Standard Time PDT Pacific Daylight Time YST Yukon Standard Time YDT Yukon Daylight Time HST Hawaiian Standard Time HDT Hawaiian Daylight Time Program JPLCLOCK Multimission Control Center Clock Page 55 GMT Greenwich Standard Time (UK) BST British Summer Time (UK) CET * Central European Time CES * Central European Summer Time * denotes non-standard abbreviation Users with specific information on time zone names, abbreviations, and and relationship to UTC as well as official times for changing to and from daylight/summer time are encouraged to send me that information so that I may update or correct the program if necessary. The information will be added to subsequent versions of JPLCLOCK. Program JPLCLOCK Multimission Control Center Clock Page 56 JPLCLOCK REVISION HISTORY ------------------------- Each released version of JPLCLOCK uses a four digit revision code such as 9126. The first two digits indicate the year and the second two digits indicate the week of the year. In some cases, an additional letter suffix is added to distinguish changes occurring within the same week. A partial week at the beginning or end of the year is counted as a full week. Using this method, a year will typically have 53 weeks although it is possible to have 54 weeks in a leap year (1972 is an example). The current year-week revision code is shown on the Julian Date display, Display Mode 7, in my program ASTROCLK. This file records the revision history of program JPLCLOCK through all of the minor twists and turns that usually accompany the evolution of such a program. It illustrates the tortuous process of maintaining and refining a program as ideas and problems are reported from every quarter. These notes may also be helpful to users who are upgrading from one version to another to find out what has changed. David H. Ransom, Jr. 9128 7/05/91 ----------------- -Repaired bug that caused CALIBRATION (F6) to fail to execute subsequent TIMESET calls at the correct time interval after the first two. Also corrected a sign error in the drift calculation during self-calibration. -Corrected screen text for CALIBRATION (F6) to show correct calibration intervals of 1, 2, and 4 hours. The total time required is 7 hours. 9127 7/01/91 ----------------- -Added "/SMALL" command line option to display smaller Main Window with Local Time and UTC Time. See text for details. -Added ALT-F6 during clock display to switch between LARGE and SMALL Main Window. -Added four additional SELECTED and PRIORITY EVENT windows below the SMALL Main Window. User may select: four SELECTED EVENTS (default); two SELECTED EVENTS and two PRIORITY EVENTS; or, four PRIORITY EVENTS. Change using ALT- F5 when SMALL Main Window is active. These additional four windows are displayed ONLY when the SMALL Main Window is selected ("/SMALL" command line option or ALT-F6 when clock display is active). -Added "/SYNC" command line option to force immediate time synchronization (using program TIMESET) when JPLCLOCK is started. The time synchronization performed as a result of the "/SYNC" command line option is independent of the automatic time synchronization (F10+F3+F3). -Changed "/TEXT" command line option so "/PAGE" is no longer also required. "/TEXT" now forces PAGE mode. -The word "HOLD" now appears above the Mission Timer windows if the current page of Mission Timers is being held on the screen because one or more of the timers is within 1 hour of its Time Zero. -Changed SCREEN FREEZE (ALT-F1) to time out in 5 minutes if no key is pressed. Current UTC and Local time are now displayed and updated on line 2 during the screen freeze. JPLCLOCK will no longer freeze indefinitely! -Changed Location Clock prompts for "Uses US Daylight Time" (F2) to "Y" for Program JPLCLOCK Multimission Control Center Clock Page 57 YES and "N" for NO. -Corrected bug in Mission Timers: countdown time at zero days displayed "0" days rather than "-0" days. -Corrected a bug introduced at Version 9126: INI files were interpreted incorrectly and reset the Daylight Flag on the Location Clocks which use US Daylight Savings Time. -In most instances, pressing BACKSPACE will reset the timer in the message "JPLCLOCK will start automatically in NN seconds". When typing characters, the BACKSPACE will delete the previous character. -Modified large clock logic in the Main Window to write only digits that have changed. This improves performance with slower computers and/or slow video adapter cards. -Improved prompts for Read/Write INI & MTD files (F5) and corrected a minor bug when ESC was pressed to CANCEL. Added warning that disk operations may affect JPLCLOCK's time accuracy. -Added warning when exiting to DOS (F9) that disk operations may affect JPLCLOCK's time accuracy. -Fixed "?" command line help so correct time is shown and added "/TEXT" command line reminder. -Corrected references to the DOS timer rate. The timer ticks occur 18.2 times per second or every 54.945 milliseconds. Previous text had the frequency given where period was indicated. -Various cosmetic changes. 9126 6/22/91 ----------------- NOTE: Program JPLCLOCK and this documentation were prepared largely from memory some hundreds of miles away from my usual references and other resources. Technical revisions and corrections can be expected in future releases! Comments and suggestions are welcome. -INITIAL PUBLIC RELEASE OF JPLCLOCK. -Added F10 to Main Menu for manual and automatic time synchronization and calibration functions. See the section TIME SYNCHRONIZATION for details. -Added automatic offset and drift compensation to JPLCLOCK displayed time based upon measured time offset and drift rate. Once the average drift rate of the computer's clock is known, JPLCLOCK will compensate for that drift and display the corrected time. -Added TEXT mode for the display of up to 10 screen pages of supplementary information or messages. A sample text file, JPLCLOCK.MSG, has been added to the standard distribution files. See text for details. -Added "bar meter" above the Main Window to provide countdown to automatic time synchronization. Meter appears 100 seconds before JPLCLOCK suspends and counts down in increments of 10 seconds. -Added two "bar meters" above the Mission Timer windows to display active Mission Timer pages and active TEXT pages. The right meter is for Mission Timer pages and the left for TEXT pages. Active page markers are in color and inactive page markers are gray. -Added "#nn" copy format to Mission Timer input (F3). -Added TAB to skip an entry and leave it unchanged in several menus. -Added F7 to switch TEXT mode from Main Menu. -Added F8 to switch PAGE mode from Main Menu. -Added ALT-F1 to FREEZE clock display. Press any key to resume operation. -Added ALT-F7 to switch TEXT mode from clock display. NOTE: PAGE mode must first be enabled before TEXT mode can be enabled. -Added ALT-F8 to switch PAGE mode from clock display. NOTE: TEXT mode will Program JPLCLOCK Multimission Control Center Clock Page 58 be disabled (if enabled) when PAGE mode is disabled. -Added F4 on the DEFAULTS menu (F4+F4 from Main Menu) to allow the user to set the PAGE Delay and the TEXT Delay. See text for details. -Swapped Location Windows #2 and #3 to make numbering scheme conform to the other windows, top to bottom in a given column. -INI file format has changed but JPLCLOCK will correctly read Version 9125B INI files and subsequently write the new format. Use F5 from the Main Menu to convert prior files; first read the old file then write a new file using the same or a new filename. -The menu message "JPLCLOCK will start automatically in NN seconds" now counts down as the allowed time for keyboard input decreases. -Various cosmetic changes and minor bug repairs. -Documentation updated. 9125B 6/16/91 ----------------- -Added /PAGE command line option for page mode operation. -Number of timers now set to 60 in 10 pages. -Mission Timer capacity changed to allow from -9,999 days to +99,999 days to accommodate long duration interplanetary missions such as Voyager 1 and 2 and Pioneer 11 as they leave the solar system. -Corrected Daylight Savings Time adjustment and default values for the four location clocks. -Added Voyager 1 and 2 to default data but times and dates are only approximate. -Function keys on several menus changed or swapped. -Many minor and cosmetic changes. -Documentation updated. 9125A 6/14/91 ----------------- -Interim test release. -Documentation not updated. 9125 6/12/91 ----------------- -First fully functional release. -All configuration features now available. -Preliminary documentation released. -Mission Elapsed Time for Magellan, Galileo, and Ulysses are NOT correct. Dummy values have been used for testing. 9124 6/10/91 ----------------- -Initial BETA VERSION Release. This version was an operational demonstration of the program and did not include any configuration features.