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Satellite Orbital Prediction Program Copyright (c) 1991 by Bill Penner, WB7DPF Version 4.03 22 December 1991 INTRODUCTION This program was written to be used to predict the position of a satellite using either standard Keplerian orbital elements or a position and velocity vector, such as the NASA M50 elements. This program was based on the orbital predication calculations found the orbit prediction program written by Dr. Thomas A. Clark, W3IWI, however, since version 3.11 I have rewritten everything to slightly improve accuracy, and to provide more information. I originally took the Apple version by Dr. W. D. McCaa, K0RZ, rewrote it for the ATARI 800XL, adding a real time component, and then rewrote it for the ATARI ST. This program is written in Megamax Laser C. The program can be ran as either an application (normal program) or an accessory. This program will run from either a floppy or hard disk and will work on the ST, STE, MSTE, and the TT computers. SETTING UP THE FILES To run the program as a program, copy all data files to a directory or subdirectory. The program does not need to be located in the same directory as the data files and can be located in another directory. I recommend that during initial use of the programs, the data files and the program should be located in the same directory. The default configuration expects the data file to be in the same directory. If you wish to locate the data files separately, read the section discussing configuration editing. If you wish to run the program as an accessory, rename the SAT403.PRG file to SAT403.ACC, and place the program on your root drive (usually C: on hard drives or A: if you boot from floppy). For easiest use, place the data files in the same directory as the accessory. If you wish, you can place the data files in a subdirectory, however, you will need to edit the program configuration. STARTING THE PROGRAM To run the program as an application, double click on the file. To run the program as an accessory, simply boot the computer with the accessory in the boot (root) drive as setup above. When the program starts, if no configuration file (SATPRED.CNF) can be found in the same directory, some defaults are assumed. The defaults will attempt to locate a satellite data file called BULLETIN.TXT in the same directory as the program or accessory, and then a reference location data file called DEFAULT.SPL, also in the same directory. SETTING UP THE PROGRAM To set up the program, once it is running, you will need to set up the information about what time zone you are in. When the program is run, you will automatically be shown a dialog box to set the time, whether to ask for the time whenever the program is started, and if we are currently in daylight savings. To adjust for daylight savings, click on the daylight savings button (the box should become checked) when daylight savings is in effect. The button, simply adds 1 hour (easterly time) to the time offset internally when it is set. Next set the "Ask time at boot" button. If you have a built in real time clock or some other program for setting the time, turn off the check mark, else when the program is started up, it will ask for the local time and offset. The next thing is to set up the location information. This file tells the program where to center the map, what location to use for the reference point for calculation of the azimuth (or bearing), the satellite elevation relative to the horizon and the difference between the computer clock time and UTC. To edit the location data, place the mouse on the [Location] button, press the left button and hold it down. While holding the button, drag the mouse to the Edit Station menu entry which just appeared next to the Location button and then let go when the mouse is above the [Edit Location Info] entry. You can also click on the [Location] button and then click on the Edit Station entry. At this point, a dialog box will appear. Fill in the location name (or call sign) to indicate where the data is for, the latitude and longitude for your location (in decimal degrees, i.e. 122.456) and then the altitude in either feet or meters. You can configure the program to use either US or metric units by clicking on the units value shown. Next, set up the offset between UTC and local time. This value should be set to 8 for the Pacific time zone or 5 for Eastern time zone for example and then the WEST button should be darkened to indicate which direction from UTC. When all of the parameters are correct, click on the [Save] button If everything started up ok, then you should be now able to click on the [Real Time Tracking] button and the first satellite in the data file will be shown on the screen showing where the satellite is located and some parameters associated with the satellite. PROGRAM DETAILS The main intent of the program is two fold. The program is intended to generate real time data for use in locating a satellite at a specific time and to generate printed information over a specified period of time. The program also provides utilities for loading, merging, editing, sorting, purging, and saving satellite orbital data. Nearly all program functions can be accessed from the main menu. The uses of the main menu options are as follows. [Satellite] The [Satellite] button will bring up a pop-up menu. On this menu, the satellite database can be loaded, saved, merged, edited, or enabled for processing. Satellite data can be saved in either ASCII or binary format. When [Save Satellite] is selected, an alert box is displayed asking for which mode to save the file in. ASCII format is to allow transferring satellite data to other programs or computer types. The ASCII file data is in the standard NASA 2 Line format. The binary format is included mainly for speed. The ASCII file does take some time to load, whereas the binary format can load nearly as fast as the screen can redraw. When [Load Satellite] is selected, the file mode is not asked as the program will automatically determine if the file is an ASCII or binary file. The [Edit Satellites] option is where the satellite orbital parameters may be entered or edited. The time data can be entered in either of two formats; year and decimal day, or MM/DD/YY HH:MM:SS.SSSS. Either the use of semi-major axis (SMA) or mean motion (MM) may be selected. This option is changed by clicking on the [MM] or [SMA] button and selecting the desired mode on the pop-up menu. The units of SMA can also be changed between meters and feet by clicking on the [meters] or [feet] button and then select the desired units from the pop-up menu. The option of entering a position and velocity vector can be accomodated by clicking on the [Enter M-50 Parameters] button. This will bring up a dialog box for the entry of these values. When [Convert] is clicked, the orbital values of Inclination, RAAN, Eccentricity, Arg of Perigee, Mean Anomaly, and Mean Motion will be filled in on the edit dialog. When entering this information, try to insure that the values are correct, as bad values can sometimes to ugly things to the software. Once a value has been converted, you can go back and edit the M50 values until you change the satellite that you are editing. Once you change the satellite, the fields will be cleared out. The [Enable Satellites] option is for choosing which satellites will be used for the desired processing. The real time and the print orbital data have two modes; single satellite and multiple satellite modes. In the [Real Time Tracking], if multiple satellites are selected, the map will alternate between the satellites with each satellite being shown separately. For more information see the [Real Time Tracking] explaination. In the printing function, the routine will print out the requested data for each of the selected satellites. In the [Enable Satellites] dialog, options are available to reorder the satellite entries, and to purge out duplicates. The [Edit File] button calls up a pop-up menu which provides the options of [Search Satellite], [Sort File], [Purge File], [Load Satellites], and [Save Satellites]. The sort will sort first by the catalog number (if one exists), else it will use the launch designator (if one exists), and last by the satellite name. The program assumes that any one satellite has a unique catalog number and launch designator so the sort is not progressive (i.e. sorting several satellites with the same catalog number, but different launch designators). The purge option will eliminate duplicate entries, keeping the entry with the most current epoch. [Search Satellite] is used to step the display up to a desired satellite so that it can be either selected, deselected, or edited. I found that with 600+ satellites in a file, it was slow and time consuming to locate a desired satellite, even when I knew where it was in the file. The search will help speed this up. In the search menu, the [Find] will begin all searches from the beginning of the data file, and [Find Next] will start the search from the second entry shown in the Enable Satellites dialog. [Location] The [Location] button will bring up a pop-up menu where the options available are [Edit Location Info] and [Load Location Info]. These options are used to load the location information from disk and to edit the information. [Print] The [Print] button brings up a pop-up menu with [Print Orbital Data] and [Print Reference Orbits]. [Print Orbital Data] is used to print out data from the start date/time to the end date/time. The times listed can be listed in UTC or local time, provided the [UTC] or [Local] buttons are properly set. Further options can be enabled to restrict the orbital data being printed out. The special restrictions are enabled by clicking on the box to the left of the option, thus placing a check in the box if the option is enabled. To deselect the option, click again; thus removing the check. Elevation limit will limit the printed inforation to orbits in which the satellite orbit is between the two selected elevations. The old In-range option would be equivalent to -5 to 90 degrees. The option now defaults to 0 to 90 degrees. The elevation is sometimes referred to as the squint angle. The In Sunlight option will print orbital data only when the satellite is illuminated by sun. This option is provided for those users who use the program to visually observe satellites, as the satellites are generally NOT visible when they are in the earth shadow. The calculation for in sun assumes the sun is a point source or in other words is the position of the mean shadow. The Between Sunset and Sunrise option is used to print data only when the data time is between local sunset and sunrise. This option was provided also for the satellite observers. As expected, it is rather difficult to observe a satellite during the daytime. The Time between __:__ and __:__ will limit the information to within the desired time range. The Altitude limit is used to restrict data to when the satellite has an altitude within the limits shown. Few satellites above 1000 km can be easily observed, so this option can limits data to when satellites are within this range. The Azimuth limit will limit orbital data to data which falls between the limits. This could be used to attempt to identify an observed satellite or to limit data to portions of the sky that you are interested in. The combination of one or more of the limiting options can be useful in determined what satellite was observed. By using the range option, the azimuth, and elevation limits, you can limit printed data to a certain portion of the sky. [Print Reference Orbits] is used to print out the south to north equatorial crossing times, orbit number, and longitude of crossing. This data is often useful for those who provide information to amateur satellite users who are using the AMSAT or ARRL orbit estimation tools (i.e. the map with the overlay). [Config] The [Config] button is used to edit the program configuration parameters. From here you can enable ground tracks and In Sun/In Shadow checking on the [Real Time Tracking] display. If you have a MC68881 or MC68882 math coprocessor in your system, you have the option of enabling the math coprocessor. When the program starts up, it scans the system for either the SFP004 (a coprocessor designed for use with the MegaST by ATARI but only sold to developers, but, also compatible with some other third party math coprocessor upgrades) or MegaSTE or a TT with either a 68881 or 68882 math coprocessor. Only the options which are available on your system are able to be selected. If you are running the program as an accessory, and if you run another program which uses the floating point chip, you will probably want to select software only so as to prevent access conflicts which could result in bad calculations. The default satellite, location, and data directory can be set to load a different file, or directory when starting up. This is useful if you want to store the data files in a different location than the program/accessory. The last item that can be set is the satellite buffer size. The buffer size is the number of satellites that can be held in the program at any one time. No changes will occur in the buffer setting if the value is not changed, however, if the value is changed, then the satellites are cleared out and a buffer will be set up provided memory is available. If not enough memory is available, then the old buffer size will be returned. When the values are set as desired, the setting can be saved by clicking on [Save] and saving the configuration to the default name of SATPRED.CNF. You do have the option of saving the configuration file to another name to provide for alternate settings. These can be loaded by clicking on [Load]. [Set Time] The button [Set Time] brings up a dialog box that will allow you to change the time, if daylight savings is in effect, and whether to ask for the time each time the program boots. To save the settings, go to the [Config] area above and save the configuration. [Help] The help button will bring up a dialog box with some quick help information. To close the box, click anywhere within the dialog. [Credits] The credits will display my name and address in case you wish to contact me. More information on contacting me is available at the end of this file. [Real Time Tracking] This is the way to display the real time tracking information. The meaning of the various parameters are as follows: Lat: Latitude of satellite Long: Longitude of satellite RA: Right Ascension of the satellite as viewed from the station location. Dec: Declination of the satellite at viewed from the station location. Alt: Altitude above ground Azim: The bearing or azimuth angle from the location position to the satellite Elev: The angle between the horizon and the satellite. This is sometimes referred to as the squint angle. Negative values indicate the satellite is below the horizon and 90 degrees indicate the satellite is straight above the location position. MA: This is a value which ranges from 0 to 255 indicating the relative position within an orbit. This is a parameter often used by satellites to indicate when a mode change is to occur. Orbit: Number of orbits completed by the satellite. Often this number is mod(32768) so that orbit number 32768 becomes orbit 0 and starts counting again. This is appearently the result of some older processing system capabilities. Vel: This is the velocity of the satellite with respect to the GHA referenced to the center of the earth. This does not include the velocity component of the earth traveling around the sun. Rel Vel: This is the relative velocity between the satellite and the location position. Under the older software, this was calculated based upon two predictions. The new calculations now calculate the instantaneous velocity and the corresponding relative velocity. Range: This is the range between the satellite and the location point. Beacon: This is the expected receive frequency for the beacon, in MHz, adding in doppler corrections. Dopple: This is the resultant doppler calculated at the beacon frequency in kHz. PeA: Altitude of satellite at Perigee. ApA: Altitude of satellite at Apogee. Inc: Orbital Inclination. Prd: Orbital Period (time required to complete one orbit). The satellite position is shown by the '*' which is within the highlighted area. The highlighted area indicates the satellite footprint or area which is visible from the satellite. If more than one satellite is selected in the [Enable Satellites] routine then the program will cycle through the selected satellites, one at a time. This can be handy if you are waiting for several satellites to come into range. Within the real time tracking window, several key commands are available. The following keys are available in either single or multiple satellite display: [F1] Increment time by 1 hour [F2] Increment time by 10 minutes [F3] Increment time by 1 minute [F4] Increment time by 1 second [F5] Restore time to system time [F9] Toggle between Right Ascension and Declination mode and Subsatellite Longitude and Latitude mode. shift-[F1] Decrement time by 1 hour shift-[F2] Decrement time by 10 minutes shift-[F3] Decrement time by 1 minute shift-[F4] Decrement time by 1 second The following keys are available in single satellite mode: [+] Step to next satellite [-] Step to previous satellite The following key is available in multiple satellite mode: [F10] Hold the display on the current satellite The change time keys are very handy to look ahead in time to check out a prospective pass. When you are done checking, then [F5] will restore the current system time. From within the configuration dialog, you can enable ground track and in sun/in shadow checks. These require additional calculations and do slow down the processing slightly. The ground track will draw a line showing the satellite track for -0.25 to +0.75 orbits. LOADING AND SAVING SATELLITE DATA Two data formats are used by this program for holding satellite data; ASCII and Binary. The ASCII format is a text file with the data stored in the NASA two-line format preceded with the satellite name and beacon frequency (if one is set). This format is slower for the program to load and save, however will allow you to trade files with other satellite programs. The binary format is not compatible with any other software, however, is much faster to load and save. The binary format will also save the enable status, so if you have a satellite or set of satellites that you like to have enabled, set the enabled status (in [Enable/Edit Satellites]) and then save the file in binary form. When you save the satellite data a dialog box will pop up asking for whether you wish to save the file as ASCII or binary. When you load a file, it will not ask, this is because the program will automatically detect the format and will load the file appropriately. CAVEATS The predictions are relatively acurate over a period of a few months (assuming the position of the satellite has not been altered by orientation burns and the like), but the best results are to maintain the newest orbital parameters available in the file. The orbital data is available directly from NASA. To receive the information, send a letter asking to be placed on distribution of amateur radio prediction bulletins to NASA, Goddard Space Flight Center, Code 513, Greenbelt, MD, 20771. If you have interest in other satellites, you can ask for prediction bulletins for those too (but you must have either the catalog number or flight and payload numbers). Once you have the data, you can enter the data by clicking on either the Edit Satellite button or by clicking on Set Satellite and then double clicking on one of the satellite entries. Two-Line data files are also available from a number of BBS's. One of the most popular is the Celestial BBS, in Fairborn, OH. The bbs number is (513)427-0764 and orbital parameters are available for nearly anything. The data is found in the various .TLE files on the system. Another excellent source of data is the GEnie computer service in the Spaceport Roundtable bulletin board. For GEnie signup information, call GEnie client services, 1-800-638-9636. The file MASTER.TLE was built from files from the Spaceport Roundtable on GEnie. COMMENTS Use this information AT YOUR OWN RISK. I assume no responsibility for any loss or damage as a result of use of this program. I have been using the program off and on for over a year and the numbers are pretty close. During the first ham in space flight, I called NASA and received orbital information for the shuttle. With this program, the prediction was within about 10 seconds (the information being broadcast on 2 meters in the Seattle area was over 5 minutes off!). In using the satellite orbital data, remember, the information is generally accurate but things do change. Many satellites maintain a particular orbit by occasionally doing burns to make adjustments. When these burns occur, the prediction will become increasingly in error (and besides, the numbers are not perfect anyway). To make sure the prediction is close, try to maintain current information. If you have any problems with this program, please leave me a message on GEnie (BPENNER). I generally log onto GEnie weekly, so I should respond fairly quickly. You can also reach me at Bill Penner, 3235 Wright Avenue, Bremerton, WA 98310 by mail, or leave a message on my BBS at (206)479-2157, or if you wish, you can call me at (206)373-4840 before 9PM Pacific Time. NOW LAST, BUT NOT LEAST, THE SOAPBOX This program is FREEWARE. In other words, this software is copyrighted software, but a license is granted for non-commercial use provided the program software is distrubuted unchanged. Do not modify the software and then distribute it, as this makes troubleshooting problems very difficult. All that I do ask is that if you find any bugs or have any ideas of things that you would like to see in this program, or any of my other programs (like my A-Real Time clock, or COMCODE, a morse code practice tool), drop me a line. SUMMARY OF CHANGES The following are changes which have occurred in this version from the previous verson of 3.11. 1. All calculations have been rederived and improved to increase accuracy and to provide more information. 2. Velocity measurements are now instantaneously calculated rather than making two position measurements and calculating the speed from the time range difference divided by the time. 3. The primary format for data storage has been changed to ASCII files (such as the .TLE files used for other tracking systems. Binary data storage is still provided as an option is this method is much faster, but not transportable to other tracking programs. 4. Many routine have been added to allow better editing and management of satellite files. Options have been added to merge, sort, and purge duplicate satellites (duplicates deleted based upon epoch date). This allows new files to be merged and then purged to maintain a file with the latest known information. 5. The satellite data buffer size has been made dynamic so the size of the buffer can be changed to user requirements. With 4MB of memory over 20,000 satellites can be manipulated. 6. A ground track has been added to the real time display. The ground track is shown for -1/4 to +3/4 orbits drawn with 32 points. For highly eliptical orbits, the line may become very segmented looking. This is during the period where the satellite velocity is very high and the altitude is very low. When the position of the satellite is drawn, the satellite will be in the correct location and may not be drawn perfectly on the line. Also, the start and end of the line are not intended to be connected, this is because while the satellite has completed one orbit, the earth has moved under the satellite. 7. The satellite footprint calculation has been fixed. In version 3.11, I indicated that the footprint did not always look right, well, it was really wrong! The footprint is now correctly calculated and agrees with the displayed elevation. 8. All dialog boxes, the real time map, and the print to screen are done in windows. Each of these windows are moveable and can be topped with other windows. In accessory mode, the windows work with the desk top directories and other accessories in a gracefull manor. 9. Better math coprocessor support has been added. The use of the math coprocessor can be disabled and support is now provided to work with the TT/MSTE math coprocessors. On the TT, if multiple satellites are selected and displayed, you may wish to disable the math coprocessor, as the step between satellites is almost to fast to see anything. The coprocessor setting is saved when the configuration is saved. 10. The graphics are now generic and should work with any display. The software has been tested on ST, STE, and TT graphics. 11. Support for orbital data in the form of a position and velocity vector has been added. This data can be entered from the edit satellite data dialog by clicking on the Enter M-50 Parameters button. 12. Alternate time formats and use of either semi-major axis or mean motion parameters may be selected by the user in the edit satellite data dialog. 13. The print routines have been modified by the addition of various filters to limit data being printed. The [In Range] option will now accept a user specified value for elevation rather than assuming -5 degrees as version 3.11 and older versions did. 14. Many of the time references will now allow the use of either local or UTC time by setting the button to the proper mode in the dialog box. 15. Sunset and Sunrise is now calculated and displayed. This data can also be used to print data only between sunset and sunrise for the use in visual observation of satellites. 16. The accessory mode has been changed as not to say anything during the booting process until the user selects the accessory. This reduces the number of dialog boxes that are encountered when trying to boot the computer. 17. Many changes have been made to clean up the internal operation of the software to ease debugging and addition of new routines. Future updates should now be easier to make. VERSION 4.01 CHANGES > Added a test to check for close passes between two object. This test can be made by selecting the object(s) you wish to compare and they are then checked against the entire data base. Be aware, the routine tries to do smart things like check to see if the orbit allows the two objects to come within a specified range of each other before making checks, however, it is slow because of the number of calculations needed. > Added more parameters that can be specified to limit the orbit data when printing. The added parameters include altitude and azimuth and elevation has been modified to include minimum and maximum elevation. Now, if you see a satellite in a certain area of the sky, you will be able to build a box around the approximate location and then to print information for all of the satellites. Only satellite data which fits the specifications will be printed. > Several bugs were fixed. One was a problem the Laser C libraries have when dealing with a -0.0. The value -0.0 is a legal value for math coprocessors and the Laser C library would enter an endless loop when formatting the -0.0 value. If you had problem with the program hanging when saving data into an ascii file, this was the cause. VERSION 4.02 CHANGES > The year shown has been expanded to four digits instead of just two. This will allow you to specify nearly any year, however, calculations don't allow much accuracy beyond a couple of weeks for low altitude satellites and a few months for higher orbit satellites. > There were several bugs in the print orbit routine using the various limits, such as between sunrise and sunset and altitude limits. The limits were not operating as they should. This is now corrected. > Quite a bit of underlying code has been modified to support future changes. > Math coprocessor routines have been improved again to fully support ST and TT type math coprocessors. Several problems were encountered when trying to use Mega STE coprocessors where the program would hang when trying to use the math coprocessor due to setup and timing problem. This has been remedied. > When switching between the coprocessor and software calculations, sometimes some values would change slightly. This was due to the math coprocessor using IEEE math rounding and the Megamax math library would not. New routines were written to handle proper rounding modes so now no difference should be noted. > The time offset between UTC and local time has been moved to the edit station dialog box and is now saved with the location information rather than the configuration data. Existing configuration and location data files will work with this program and the files will be updated when saving the data files back to disk. > Doppler frequency has been removed from the printout if no doppler frequency for a satellite is set. > Print to screen would not display the degree symbols and then the header spacing was not correctly set up. This is fixed. The speed of printing to the screen has been slightly sped up. > A problem in saving ASCII data files was noted which would write out strange characters in the BSTAR field of the two-line parameters. This has been fixed. > Two parameters were added to the edit satellite dialog; mean motion rate rate (second derivative of mean motion) and BSTAR/AGOM. The BSTAR/AGOM parameter is not used, but you can now edit the value anyway. > If satellite elements were of a date either before 1980 or after 1999 the program would complain about the date not in a table. This problem has been removed and the program will now support any date of elements. > Function keys were modified slightly, now F2 will increment time by 10 minutes, F3 will increment time by 1 minute, F4 increments time by 1 second, and F5 will restore the system time. Shift-F1 through Shift-F4 will decrement the time. VERSION 4.03 CHANGES > A major bug in the shadow routines caused the shadow data to be shown as if the sun was always located at 180 degrees longitude. The shadow stuff worked in 4.01, but when I upgraded much of the internal routines, I forgot to update all of the shadow routines. The shadow routines now appear to be working correctly. In case your curious, the internal modifications were to convert the internal calculations from using a date referenced from Jan 1, 1970 to a julian date. This was the change that was referenced in the changes since 4.01 information below. > When displaying tracking data for multiple satellites, you can now hold on a specific satellite by pressing the [F10] function key when the desired satellite data is being displayed. Upon pressing the F10 key, the program will delay for a short time, display the word 'Hold' in the lower right corner, and will then continuously update the parameters as if a single satellite was selected. To continue cycling through the various satellites, press [F10] again to turn off hold mode. > Screen updates were changed to make the update smoother and to decrease the amount of bad data being displayed when starting up the map or changing the time or satellite while displaying data. > When printing data, two changes were made. Now, when you select an output for printing (file, printer, or screen), the next time you print, the default will be set to the last selected button. Before, the printer was always the default. The printed header was also changed so when daylight savings is selected, a '(DS)' will be printed next to the time mode (local or UTC) to inform you that daylight savings mode is selected. Since all calculations in the program are based upon UTC time, the daylight savings flag is very important to be properly set to know how to calculate the UTC time from the computer (local) time. VERSION 4.04 CHANGES > Right Ascension and Declination can now be selected for the map display and for printing orbital data. In the map, this mode may be toggled by pressing [F9]. In the print orbital data dialog, a check box was added to select Right Ascension and Declination. > I made some changes in the calculations dealing with period, apogee, perigee, and associated items for satellites that have a significant decay rate. Before the program would assume that the orbit size would remain the same, but now, it will properly calculate the current period, and then adjust the orbit size for all of the calculations. The problem was noticed when old data was used for a satellite that had a high decay rate. The program would plot the ground track for more than one orbit (and sometimes several) and then the velocity, perigee, apogee, and period did not make sense (too low). Now the values are much more reasonable and comments have been added to the program when a satellite is below ground 8^). > I make one simple text change. I changed the phrase "In Sun" to "Sunlit" on the map screen, to be more correct. > I reformatted the map screen a little bit, so now altitude at perigee, and altitude at apogee, inclination, and period are now shown. > You can now turn off the page feeds in the print orbit routine. The page feed was sent at the end of each page in addition to the page feed following each satellite. > A bug was found so that when the time offset between local and UTC was changed, the program would not use the value unless the time dialog was entered and exited, or the location data saved and the program restarted. This problem is fixed. > A bug in the print orbital data where when form feeds were turned off between satellites, the satellites following the first one did not have the satellite name printed. The satellite names now print correctly. > An option was desired to be able to sort the satellites by satellite name rather than satellite catalog/designator/name. This option was added. > An option asked for was to be able to only save enabled satellites to a satellite data file. This options has been added. To support this and the sorting options, the menus were rearranged. > The merge operation was moved to the edit active satellite dialog. This moved all of the data editing options to one place as the merge option was out of place on the main menu. > A bug was fixed in the Enable/Edit Satellite routine which would cause the program to hang if Load Satellite data was selected from this point. The data would load, but then the program forgot to redraw the enable/edit dialog again. WHATS NEXT? Well, I am in the process of adding a sky display, showing a portion of sky with a star background and the displaying the position of a satellite in respect to the stars. Do you have any other ideas that you would like to see? If you do, or if you find something that does not work as you expect, please let me know and I will do my best to get things changed. Bill Penner, WB7DPF Phone: (206) 373-4840 before 9pm Pacific time BBS: (206) 479-2157 GEnie: BPENNER ATARI is a trademark of Atari Corporation, GEnie is a trademark of The General Electric Company.