GEOST 2.3, Geo-Stationary Satellites' position Copyright 1992-97 Giuliano Artico I3LGP Address: Via Belzoni 7, 35131 PADOVA, Italy Phone : 049 827 59 09 E-mail : artico@math.unipd.it WWW : http://www.math.unipd.it/~artico AX25 : I3LGP@IW3GRX.IVEN.ITA.EU C O N T E N T S 0. Program installation. 1. Introduction and general information. 2. Observer window and location setting. 3. Satellites window and setting. 4. Storage of locations. 5. Output. 6. Format of the configuration file. 7. Data bases and viewer. 8. Options on the DOS command line. 9. How to determine the QTH locator. 10. Setting of the antenna system. 旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� � IMPORTANT � � Before running the software GEOST, � 쿶t is necessary to read the file LICENSE.TXT.� 읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 0. Program installation. To install the program GEOST, simply run the self-extracting compressed RAR archive GEOSTnn.EXE (where "nn" is the version number identification). All the files must be placed in the same directory.There is no restriction on the installation directory name, but it is convenient to add it to the system path, in order to make the program accessible from anywhere within the system. If the existing path is too long to accept new directory names, one may assign the directory name to the "GEOST" environment variable, by using the SET command (in this case the program sould be called with its full path specification). For instance: C:\>set geost=c:\satellit C:\>c:\satellit\geost The above mentioned distribution archive is equipped with the following RAR autenticity verification string: Giuliano Artico, Dip. di Matematica P.A. - Padova The package GEOST consists of the following files: LICENSE.TXT license; GEOST.EXE executable file; GEOST.TXT manual (this file); WHATSNEW.TXT short description of changes; GEOST.DAT example of configuration file (ASCII text file); GEOST.INI example of initialization file; QTH.LOC data base containing geographic information on about 1300 sites; SATELLIT.TXT satellites data base (Europe); GEOST.LOG file for data logging (generated by GEOST as output on disk); GEOST.SAT locators storage file (for compatibility with version 1.21). 1. Introduction and general information. The program GEOST is designed as an aid for the installation of antenna systems for geo-stationary satellites. All such satellites are placed in a circular orbit above the equator. Their angular velocity is equated to the angular velocity of the earth, in order to maintain each of them always above the same point of the earth surface. Therefore, tracking a determined geo-stationary satellite is a trivial operation, as any observer sees it as a motionless object in the sky. However, the problem which arises is that of installing the antenna system in such a way that it is always directed towards points lying on the orbit of geo-stationary satellites, when it is rotated in any direction, since in this way it turns out to be easy to have access to different satellites (section 10). The program GEOST supplies the values of azimuth and elevation for a set of five satellites, chosen by the user in appropriate way with respect to his location. Three of them are referred to as "pilot satellites" and we shall call them "Western", "Central" and "Eastern" respectively (see section 3). One should assume as "Central" the satellite which is more or less positioned on the same meridian circle as the site of the user. The "Western" and"Eastern" satellites are the extreme ones in the West and East directions respectively, among the ones which the user wants to receive. Pilot satellites may be changed interactively within the session of the program. Two more satellites are the "bounds" and ought to be choosen as the extreme ones visible from the observation point. The program always displays the elevation under which the antenna sees the culminating point of the geo-stationary orbit: this value is generally equal to the elevation of the central satellite, if its choice has been made in a reasonable way. The last value provided by GEOST is called "correction" and is the difference between the direction of the meridian of the observer and his azimuth bearing for the central satellite. This value allows an easy calibration of the geographic orientation: in fact, the compass is not accurate enough for our goals. The difference is computed with respect to the South direction for the points on the boreal (northern) hemisphere and with respect to the North direction for the points on the austral (southern) hemisphere. The following data are required as input: - the position of the observer; - the longitude of all five satellites; - some optional data dealing with the output on disk or printer. Latitude and longitude are always decimal numbers: for instance, 12 degrees and 30 minutes are shown (and must be entered) as 12.50 degrees. Observe that the west longitude and the south latitude are assumed to be negative numbers. For the above data, default values are assumed if necessary. For the position of the observer, two different formats are recognized: - the Maiden Head Grid Square notation, referred to as QTH locator (see section 9); - the geographic latitude and longitude. Satellites' and geographic information may be loaded interactively during a session from two data bases (section 7). Three kinds of output are supported: - to the screen: this is useful for interactive operations; - to a standard ASCII text file; - to a printer. For the second and third option, two types of format may be selected (see section 5). The software GEOST may be configured by storing "home" information (location of the receiving station, longitude of pilot satellites, parameters for the printout) in the file GEOST.DAT: if such file does exist and its format is valid, then the information contained in it are automatically loaded at the start up. Some data may be also entered at the DOS prompt, by using the appropriate options. Furthermore, the situation existing at the end of a session is memorized in the initialization file and presented when the program is run again. In the case that an interesting location must be examined again later on, it is possible to store it by means of the appropriate function key. GEOST incorporates a simple file viewer that allows to browse all the information provided with the package (manual, data bases, license,...) and, optionally, also a user-defined file. Eac file is associated to a specific key combination (see section 7). The list of available commands may be displayed by pressing the "?" key (question mark). Finally, a help screen is shown by typing the character "?" as argument at the DOS prompt after the name of the executable file GEOST.EXE. 2. Observer window and location setting. The information provided by GEOST are displayed in two windows, the "satellites" window and the "observer" window. One may switch between them by pressing the Tab key. Four fields (site, QTH, latitude, longitude) may be edited and the entered values are immediately assumed when the Return key is pressed or when any other function is invoked. The position of the receiving station may be entered in two different formats: the so called "QTH locator" and the geographic latitude and longitude. The user may adopt the whichever he prefers. Five different ways of supplying the QTH locator are available: 1) by editing the appropriate line in the configuration file GEOST.DAT; 2) with the option /Q at the DOS prompt (the option /Q has priority with respect to the locator stored in the configuration file); 3) within the program, by editing the field "QTH"; 4) within the program, by retrieving one of the ten stored locations; 5) within the program, by using the movement keys. The locator entered in the modes 1 and 2 is overridden by the one stored in the initialization file, but it may be restored by pressing the Ctrl-Home key when the cursor is placed anywhere in the "observer" window. The geographic co-ordinates may be entered by editing the "Lat" and the "Long" fields in the observer window. The first field may contain the name of the location or a comment sentence. Once the location is entered, the program calculates and displays the following information: - the location in both formats; - azimuth and elevation for all satellites (shown in the satellites window); - the maximum elevation of the antenna ("Peak" field); - the correction for reaching the direction of the meridian plane starting at the direction of the central satellite ("Corr" field). The location may be adjusted interactively by pressing: - Ctrl with the arrow keys to get a small shift; - Alt with the arrow keys to get a big shift. The pressed arrow is the one corresponding to the desired cardinal direction. In this way one can reach the desired position through successive adjustments. It should be noticed that the QTH locator is less accurate than geographic co-ordinates: therefore, when the location is defined through the first notation, an average value is computed for longitude and latitude and a round-off error may occur. About the /Q option and the format of the configuration file, see below. 3. Satellites window and setting. The program GEOST provides the azimuth and elevation for five satellites: three of them are chosen by the user with regard to his particular situation. This feature allows the highest accuracy, since it facilitates detection of any difference between computed and measured values, by comparing results for the five objects. The longitude of each satellite may be input by editing the appropriate line in the configuration file GEOST.DAT. The three pilot satellites (western, central and eastern) may be selected interactively by first moving to the satellites window and then by pressing the Ctrl-UpArrow or Ctrl-DownArrow keys. The "bound" satellites are fixed and the above kind of selection does not apply to them. The range of longitude for pilot satellites is from -180 to 180 degrees and is a decimal number. Notice that West longitudes must be preceded by the sign "-" since they are negative numbers. Default values are adopted, if the configuration file is missing or if it does not contain the information for one or more satellites. The features of a satellite (frequencies, type, encoding and so on) may be displayed by pressing the return key on the name of the satellite. In fact, GEOST incorporates a viewer which allows to browse an external ASCII text file, in this case the file which contains the satellites information. The same file may also be accessed by pressing the combination Alt-S: this command is available also from the observer window. 4. Storage of locations. It is possible to register permanently on disk some locations which may be useful in the future. The list of stored locations is present at any time on the screen and any of them may be retrieved simply by pressing the corresponding function key (from F1 to F10). When the location is loaded, the related calculation is performed and the new information appear on the screen. From that moment onwards, that location is the one to which the movement keys apply. Conversely, to store the location present on the screen, just press the appropriate function key together with the Ctrl key. Look at the list of stored locations to choose an empty record. In any case, to overwrite an existing location it is enough to press the corresponding key combination twice. This procedure guards against the accidental loss of data. Observe that the location storage is made by geographic co-ordinates, which are more accurate than the QTH locator. Stored locations are saved in the initialization file GEOST.INI. If the program is installed by overwriting the previously installed version 1.2, it automatically recognizes the information contained in the file GEOST.SAT (which may be deleted after the first run of GEOST 2.x). 5. Output. The results of the calculation made by GEOST are presented on the screen or may be sent to a printer connected to the parallel port LPT1 or to a file named GEOST.LOG. The data displayed on the screen in any moment are relative to a single location and may be changed interactively. On the contrary, the information for the printer or for the log file consist of the values for two possible sets of locations: - the stored locations, discussed in the section 4; - the locations contained in a rectangular region centered on the location displayed on the screen. To register the data relative to these sets in the log file, one must press the Alt-F key combination. Similarly to send the output to the printer one has to use the Alt-P combination. After pressing one of these keys, the program prompts for the desired set of locations. In the log file or printer output, the values relative to every location are contained in a separate line. Explanatory headings are put at the top of every column. Due to the second option, the region for which data are computed turns out to be defined by three parameters which may be entered either through the configuration file (see section 6) or with suitable options at the DOS prompt. The distance between the points of the grid, into which the above mentioned region is subdivided, is called "Increment" and corresponds to the external option /I. The unit of measure is minutes of angle. Within the program,this parameter may be adjusted with the Alt-I combination, in steps of 5 minutes, in the range from 5 to 60 minutes. The region can be thought of as a big rectangle whose horizontal size (in the longitude sense) and vertical size (in the latitude sense) are defined by the options /H and /V respectively. The unit of measure for these parameters is the increment amount described above and they may range independently from 1 to 21. These parameters may be changed with the Alt-H and Alt-V combinations respectively. The default values for the above parameters are 15 minutes for the increment, 9 and 5 for the horizontal and vertical size respectively. The region is scanned row by row from North to South and the locations in every row are listed going from West into East. The character "*" (asterisk) identifies the first location in every row. The total number of locations contained in the defined region is displayed on the screen and this value supplies an estimation of the number of pages which would be printed. The size in lines of a printed page is defined by the option/L on the DOS command line or via the configuration file. Within the program, this parameter can be adjusted with PgUp and PgDn. The values for horizontal and vertical size are odd numbers and the program rounds any value for these parameters to the smallest odd number greater than or equal to the given one. When output data are written to the log file, the previously existing data are not deleted because the new ones are appended at the end of the file. The operation may be successful only in the case that the first line of the file contains the validation sentence "GEOST.LOG - Output file": if the file does not exist, then a new one is generated with the correct heading. Notice that if the printer is connected to a port other than LPT1, then the output must be re-directed to it before running GEOST by means of the DOS command MODE. For instance, if the port is COM2, use the following command: C:\>mode lpt1=com2 6. Format of the configuration file. The configuration file allows the personalization of the program GEOST, so that any user may start the program with the desired values for all parameters. The configuration file is a standard ASCII text file which may be edited with any text editor or word processor. The program GEOST recognizes this file as valid only if the first line contains the following sentence: GEOST.DAT - Configuration file If a line contains a character "#", all the part of that line to the right of this character is skipped, so that any line may include a comment. Every parameter is associated to a key-word which must be put at the beginning of a line and followed by the corresponding value. Parameters should be supplied as in the next example (these values are the default ones): GEOST.DAT - Configuration file QTH-Locator= JN55WJ "Padova" #Observer's QTH Locator and site name WestBound =-53.0 "INTELSAT 706" #used if satellites data base is missing WesternSat =-27.5 "INTELSAT 601" #western satellite CentralSat = 13.0 "EUTELSAT II F1 / HOT BIRD" #central satellite EasternSat = 19.2 "ASTRA 1A 1B 1C 1D 1E" #eastern satellite EastBound = 85.0 "STATSIONAR 3" #used if satellites data base is missing Increment = 15 #Distance in minutes among the locations to be printed Horizontal = 9 #Number of locations of the region in the longitude sense Vertical = 5 #Number of locations of the region in the latitude sense PageLength = 63 #Number of lines per printed page MarkColor = 0 #Marked color, values from 0 to 15, 0=reverse TextFile = *geost.dat The last line assigns the name of any text file, which may be displayed during a GEOST session by pressing Alt-T. This file name may include a full path specification. The leading character "*" is optional. It is an abbreviation which denotes the name of the directory in which GEOST is installed. The configuration file may also include a section telling GEOST how to understand satellites information taken in the satellites data base (this matter is discussed in the section 7). 7. Data bases and viewer. The program GEOST is equipped with two data bases: - QTH.LOC contains a set of locations with geographic information; - SATELLIT.TXT the list of geo-stationary satellites visible from Europe. Both data bases are standard ASCII text files, which may be easily updated by adding new data (their format is described below). Both data bases may be accessed in two ways: - to import a piece of information directly into the program; - to wiew and browse the entire list. Locations data base. To import a location, move to the first line in the observer window and enter the name of a location (or part of it, not necessarily a beginning part). When the return key is pressed, the displayed string is searched in the data base and only matches at the beginning of records are accepted. If the result of this inquiry is negative, the data base is scanned again and all matches in any position within records are assumed as valid. For instance, the following record is loaded on the second scan when entering one of the strings "ALFREDO" or "JN65DR": IK3IEO Alfredo; jn65dr The entire file QTH.LOC may be viewed, with the built-in browser, by pressing the Alt-L combination. It is possible to add information to the data base by pressing one of the combinations Alt-A and Alt-W. In both cases, the displayed location is appended to the file QTH.LOC as the last record (provided that the current site isn't already present somewhere in the data base). When pressing Alt-W, the QTH locator is written in place of geographic coordinates. The file QTH.LOC is an ASCII text file which may be updated by using any ASCII text editor. Any line of the file is a record, with the exception of the first one, which must contain the word "QTH.LOC" starting at the first position. This word is used as a validation key. The semicolon ";" is used as field separator. Any line may contain three fields: the name of the site, its latitude and its longitude, in this order. Optionally, the second and third field may be replaced by a single field, containing the QTH locator. The following records are valid: Padova; 45.41; 11.88 Padova; JN55WJ All lines containing invalid data and all lines beginning with a ";" character are discarded. For instance, the following records would be ignored: ;... (any text) Padova; 91.5; 11.88 Padova; 45.41; 3000 Padova; SS65ZZ Satellites data base. The default satellites list SATELLIT.TXT is provided by Mr Husted (Denmark) and is available via Internet at the URL http://login.dknet.dk/~husted/satellit.zip. If the SATELLIT.TXT file is missing, then GEOST looks for the Ralph Krueger's satellites list ESAT.TXT. GEOST uploads the satellites list at the start up. During the program session, satellites may be selected by pressing Ctrl-UP and Ctrl-Down within the satellite window. The file may be viewed by pressing the return key or the Alt-S combination (the return key causes the file to be shown at the position of the desired satellite). GEOST assumes that the information related to any satellite are placed in a block, preceded by an header line which includes the name and the longitude of the satellite. Adopting the style used in the file SATELLIT.TXT, the list of satellites is made up by loading the lines which contain the strings " East " or " West ". For instance: 19.2 East ASTRA 1A 1B 1C 1D 1E Dish size: 0.6 m Here are the criteria used by GEOST to extract the name and the longitude: - the name field goes from the 13th to the 45th column; - the longitude field goes from the 1st to the 5th column. A different criterium may be defined in order to replace the satellites list. To do this, one must modify appropriate instructions in the configuration file GEOST.DAT as follows: - name of the file: Sat_File=SATELLIT.TXT - strings identifying valid header lines: Sat_East=" East " Sat_West=" West " - left (LB) and right (RB) bounds of the name and longitude fields. Any of these values may be either a number (column position) or a delimiter string (strings must be surrounded by double quotes): Name_LB=13 Name_RB=45 Long_LB=1 Long_RB=5 As another example, here are the instructions for the Ralph Krueger's list: Sat_File=ESAT.TXT Sat_East="� East)" Sat_West="� West)" Name_LB=1 Name_RB="(" Long_LB="(" Long_RB="�" Built-in viewer. To invoke the built-in viewer, one must press a suitable key combination. The corrispondence between files and keys is as follows: LICENSE.TXT -> Alt-D QTH.LOC -> Alt-L GEOST.TXT -> Alt-M GEOST.LOG -> Alt-O SATELLIT.TXT -> Alt-S ... -> Alt-T The Alt-T combination is used to view a user-defined text file, whose name may be assigned in three ways (configuration file, option "/T", environment variable GEOST_TXT). The following commands are available to navigate within the text: Esc = exit viewer; Up/Down arrow = one line up/down; PgUp/PgDn = one screen up/down; Home/End = beginning/end of file; Ctrl+Up/Down = previous/next text block (separators are blank lines); F2 = enter a search string; Alt+Up/Down = search onward/backward. 8. Options on the DOS command line. Some parameters may be supplied to GEOST by means of suitable options on the DOS command line when the program is run. Any option consists of a slash "/" followed by a letter: the value of the associated parameter must be typed immediately to the right of this letter. For example, to enter the QTH locator JN65HQ, use the option /Qjn65hq(case insensitive). The list of valid options is shown when a "?" character appears as argument on the DOS command line. Valid options are: /Q... Observer's QTH Locator and site name /Cnn Marked color (0-15, 0=reverse) /Inn Increment, the grid width for the region printout /Hnn Number of locations of the region in the longitude sense /Vnn Number of locations of the region in the latitude sense /Lnnn Printed page length (in lines) /Tfile text file to be viewed with Alt-T On the command line, one or more options may be entered in any order: if an option appears twice, then only the first occurrence is assumed. Example: C:\>geost /q io92og "Northampton"/l60 /i30 sets the location to Northampton, whose QTH locator is IO92OG, the number of lines per printed page to 60 and the distance between points of the printout grid to 30 minutes. The "/T" option allows to assign the name of any text file to be viewed during a GEOST session by pressing Alt-T. The value entered with this option overrides the one provided in the configuration file. 9. How to determine the QTH locator. The Maiden Head Grid Square notation or "QTH locator" is well-known to Amateur Radio Operators. The QTH locator is an abbreviation for the geographic co-ordinates and it is very useful since, due to its concision, it may be used to designate quickly any point on the earth's surface, with a satisfactory accuracy for most purposes. The algorithm for determining the QTH locator when the geographic co-ordinates are given is sketched below. In any case, this calculation is automatically performed by GEOST, so that this section may be skipped. The QTH locator consists of six characters, subdivided into three groups: two letters from A to R, two figures from 0 to 9 and two letters from A to X. The first character in any group is related to the longitude, the second one to the latitude. First group: 18 characters are available from A to R, so that 360 degrees of longitude from -180 to +180 degrees are divided into portions of 20 degrees, while 180 degrees of latitude from -90 to +90 degrees are divided into portions of 10 degrees. In this way we have 18*18=324 large pieces of the earth surface. Second group: each of the above pieces is subdivided into 10 parts along both dimensions, so that it contains 100 "squares", with the size of 2 degrees and 1 degree for the longitude and for the latitude respectively. Third group: 24 characters from A to X are used to denote 24*24=576 spots in any square. The longitudinal (horizontal) size of every spot is 120/24=5 minutes, while its latitudinal (vertical) size is 60/24=2.5 minutes. The directions into which the angles are measured go from West to East for the longitude, starting at the -180th meridian, and from South to North for the latitude, starting at the -90th parallel (South Pole). For instance, suppose we want to calculate the QTH locator for the following location: Longitude: 11 degrees 38 minutes 40 seconds East Latitude : 45 degrees 41 minutes 5 seconds North In view of the last remark, these values are translated as follows: Longitude: 11+180=191 38 40 Latitude : 45+ 90=135 41 5 We begin calculating the first character of the three groups, by using the longitude value. First group: the integer part of the quotient 191/20 is 9, so we take the 10th letter J. Second group: the remainder of the above quotient is 11. Since the squares have a horizontal size of 2 degrees, we take the integer part of the quotient 11/2 which is 5. Third group: the remainder of the above quotient is 1. We reduce it to minutes and add the portion of degree given by minutes and seconds: 60 + 38 + 40/60 = 98.7 Since every spot has an horizontal size of 5 minutes, we must take the letter T, which is the 20th one: in fact, 98.7/5=19.7. A similar calculation must be made to determine the second character of the three groups, by operating on the given latitude. We need only use the vertical sizes of the various portions, which now are 10 degrees, 1 degree and 2.5 minutes respectively. First group : 135/10 13 N Second group: 135 - 13*10 5 5 Third group : 41.1 16.4 Q Therefore the QTH locator we are looking for is JN55TQ. One may also perform the converse calculation to determine the geographic co-ordinates, if the QTH locator is known. Obviously, in this case a rounding error may occur. Notice that the QTH locator cannot be computed for the two poles, since for such points the geographic longitude is not defined. 10. Setting of the antenna system. To install an antenna system for geo-stationary satellites, it is necessary to set the following once and for all: - the antenna rotation axis must be parallel to the earth rotation axis; - the elevation must be fixed at the proper value. When this is done correctly, the antenna may be rotated on its axis and it always "sees" points of the geo-stationary orbit, which is a circle concentric with the equator and with a radius of 42234 Km. Observe that the peak position of the system along its rotation should result exactly when the antenna is beaming into a direction parallel with the plane of the meridian circle. To obtain this, the following steps are to be performed, by using appropriate measuring devices (compass, goniometer): - ensure that the basis is perfectly horizontal; - with the help of a compass, point the system South: this direction will be corrected later on; - settle the antenna axis with an inclination equal to the latitude, with respect to the horizontal plan: this setting must be as accurate as possible and should not be modified in the following; - by rotating the system on its axis, bring it to the peak position; - look for the strongest signal of the central satellite, by rotating only the system base and adjusting the elevation (in this step the antenna should not be rotated on its axis); - if the resulting azimuth does not coincide with the one provided by GEOST, it is necessary to make an adjustment, by rotating only the base of the system, for an amount equal to the value called "correction". The last alignment is due to the deviation of the magnetic South with respect to the geographic South. If the real elevation and the one given by GEOST coincide, then this is the final position of the system. A little difference occurs, hence a little correction of the elevation is needed, when the central satellite's longitude disagrees too much with the observer's longitude. If the divergence is too large, then the process is to be repeated with higher accuracy. A further verification can be done by comparing the values for the western and eastern satellites.