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Program ORBITEL Verify and Sort 2-Line Orbital Elements (C) Copyright David H. Ransom, Jr., 1992,1993 All rights reserved. Version 9333 August 14, 1993 by David H. Ransom, Jr. Rancho Palos Verdes, California, USA Bulletin Board Systems ---------------------- RPV ASTRONOMY BBS (310) 541-7299 @ 14400/9600/2400 Baud RPV HOTLINE BBS (310) 544-8977 @ 2400/1200 Baud Program ORBITEL Verify & Sort Orbital Elements Page i ORBITEL Verify and Sort 2-Line Orbital Elements by David H. Ransom, Jr. Introduction ------------ Program ORBITEL is a utility program to verify, merge, and sort standard 2-line orbital elements files such as those posted on my bulletin board systems and elsewhere. I use the program routinely to produce the TLEnnn.TXT and GSFCnnn.TXT files from "raw data" obtained from TS Kelso's Celestial BBS and the Goddard Space Flight Center's OIG RBBS respectively. In both cases, the "raw data" consists of two or more files with differing names and sometimes non-standard format (OIG RBBS) which must be merged and then sorted to produce the final output file. Perhaps from force or habit, most sources are sorted in ascending order of NORAD number; I prefer to sort in descending order so that more recent satellites are near the beginning of the file. ORBITEL can also be used simply to verify and correct the checksums at the end of each line of a 2-line element set. For individuals who create or modify their own 2-line elements, this avoids the tedious and error-prone task of doing the job manually. Be aware, however, that a file with one or more checksum errors may contain data errors and should be carefully checked before use. It is important that the checksums be set correctly; while certainly not foolproof, the checksums do provide a quick check of the data and can detect single digit errors. Unfortunately, the simple checksum method used, modified modulo ten on each data line, will not detect digit transpositions -- one of the more common manual errors. Nor will it necessarily detect multiple digit errors on a single line. Far better error detection and correction techniques are now available but the 2-line element format was devised many years ago (as "2-Card Elements", harking back to the days of punched cards) and the format is deeply imbedded in many programs. Changing the format at this late date is thus unlikely. ORBITEL has progressed by fits and starts over the past several years as I find a need for various tools to work with NASA/NORAD 2-line elements. ORBITEL does not test the validity of the orbital data itself, only the structure of the file and the checksums for each data line. Various sort and batch mode options are included. David H. Ransom, Jr. 7130 Avenida Altisima Rancho Palos Verdes, CA 90274 Program ORBITEL Verify & Sort Orbital Elements Page i Running Program ORBITEL Interactively ------------------------------------- ORBITEL may be executed either interactively or in batch mode. To use the program interactively, enter "ORBITEL" at the DOS prompt. The following menu appears: Program ORBITEL: Verify/Sort NASA 2-Line Orbital Elements Version 9329 by David H. Ransom, Jr. F1 Display Information on 2-Line Elements F2 Display 2-Line Element Data by Satellite F3 Verify line checksums and file structure F4 Write new sorted file with corrected checksums ESC Quit program ORBITEL Enter desired function: Press the indicated Function Key to perform the desired function or press the key marked "ESC" to return to DOS. F1 Display Information on 2-Line Elements ------------------------------------------ This function displays a series of brief help screens describing the structure of 2-line orbital elements. See the section "2-Line Orbital Elements" below for similar information. F2 Display 2-Line Element Data by Satellite -------------------------------------------- This function displays the orbital data for a specific satellite. Two prompts are displayed: Enter 2-Line Elements FILENAME: Enter desired SATELLITE NAME: For the FILENAME, enter the name of the 2-line elements file; if you omit the filetype, ".TXT" will be used automatically. For the SATELLITE NAME, enter sufficient letters to unambiguously identify the desired satellite; for example, "STS" will normally be sufficient to identify a space shuttle mission. For either prompt, upper or lower case may be used. ORBITEL searches through the specified file and attempts to locate a satellite whose name matches the one requested. If found, the 2-line orbital elements data is displayed as read from the file: Element Record: 1 STS-44 2-Line Elements for STS-44 [STS44N01.TXT] 0 Satellite Number 21795 1 Launch Year 0 2 Launch Number 0 Program ORBITEL Verify & Sort Orbital Elements Page i 3 Piece of Launch 4 Epoch Year 91 5 Epoch, JD+frac 329.35841039 6 1st Deriv Mean Mot'n .00038 7 2nd Deriv Mean Mot'n 0 8 BSTAR Drag .000275 9 Ephemeris Type 0 10 Element Number 1 11 Inclination 28.4689 12 RA of Ascending Node 248.6938 13 Eccentricity .0024211 14 Argument of Perigee 196.5249 15 Mean Anomaly 163.4609 16 Mean Motion 15.62614298 17 Rev # at Epoch 7 Press any key to continue ... Press any key (except non-typing keys such as SHIFT or CTRL) to view additional derived data for the satellite: Derived data: Epoch JD#: 2448585.8584104 Epoch Time (UTC/GMT): 8.6018494 8:36:06.66 Epoch Date (DD/MM/YYYY): 25/11/1991 Launch JD#: 2448584.4216158 (estimated) Launch Time (UTC/GMT): 22.1187790 22:07:08 Launch Date (DD/MM/YYYY): 23/11/1991 Mean Orbit Time: 92.1533 min Osc Orbital Time: 92.2412 min Mean SemiMajor Axis: 6758.2500 km Orbital Altitude: 380.1150 km 204.8778 nm Orbital Perigee: 363.7526 km 196.0586 nm Orbital Apogee: 396.4774 km 213.6969 nm Press any key to continue ... Press any key (except non-typing keys such as SHIFT or CTRL) to return to ORBITEL's Main Menu. The Epoch JD#, Time, and Date restate the time of Epoch for the elements (the instant for which the elements were calculated) in more conventional notation. The Launch JD#, Time, and Date calculate an estimated launch date based upon the Rev # (orbit number) at Epoch. CAUTION: NORAD is not always consistent in the way in which it assigns orbit numbers and some very strange dates can result. At best, the launch calculations will yield a very rough approximation of the actual time and date for the launch of the satellite. The orbital data contained in the 2-line elements are adjusted in a variety of ways for use with the SGP4 and SDP4 mathematical orbital models. The additional derived orbital data take into account these adjustments and Program ORBITEL Verify & Sort Orbital Elements Page i are calculated as of the Epoch time for the elements. Orbital altitude, perigee, and apogee are given in both kilometers and nautical miles and assume a spherical Earth with a mean Earth radius of 6378.135 kilometers. F3 Verify line checksums and file structure -------------------------------------------- This function verifies the checksums on the two data lines and validates the structure of the 2-line elements file. You will be prompted for the filename to check; if you omit the filetype, ".TXT" will be used automatically. Enter 2-Line Elements FILENAME: As ORBITEL checks each record in the file, a brief listing is displayed for each satellite: Record 836: 00047 TRANSIT 2A R/B Launched 1960 Record 837: 00046 SOLRAD 1 (GREB) Launched 1960 Record 838: 00045 TRANSIT 2A Launched 1960 Record 839: 00029 TIROS 1 Launched 1960 Record 840: 00022 EXPLORER 7 Launched 1959 Record 841: 00020 VANGUARD 3 Launched 1959 Record 842: 00016 VANGUARD 1 R/B Launched 1958 Record 843: 00012 VANGUARD 2 R/B Launched 1959 Record 844: 00011 VANGUARD 2 Launched 1959 Record 845: 00005 VANGUARD 1 Launched 1958 END-OF-FILE. Press any key to continue ... Reading from the left, the colums are: record number within the file; NORAD number for the satellite; satellite name (15 characters max); and launch year if specified. The sample, taken from the end of a large file, indicates that 2-line elements for a total of 845 satellites is included in the file. Press any key (except non-typing keys such as SHIFT or CTRL) to return to ORBITEL's Main Menu. F4 Write new sorted file with corrected checksums -------------------------------------------------- This function sorts a specified 2-line elements file, correcting any bad checksums in the process. You are first asked to select a sort method: Sort and check 2-line elements file: A = ASCENDING sort D = DESCENDING sort N = NO sort Enter desired sort method: Sorting is performed using the NORAD number for each satellite in the file. You may choose to sort in ascending or descending order or you may elect not to sort the file. Press the letter corresponding to the desired sort Program ORBITEL Verify & Sort Orbital Elements Page i method. I recommend using the descending sort method since more recent satellites will then be placed near the beginning of the file and will be accessed more rapidly by other programs. You are then asked to select the file to process: Enter 2-Line Elements FILENAME: NASA085.TXT Enter the name of the desired file. If you omit the filetype, ".TXT" will be used automatically. ORBITEL then reads and optionally sorts the file, displaying the following information during the process: 14:20:44 Now reading satellite records ... 845 Satellite Records read 14:20:55 Now sorting by DESCENDING satellite number ... 2 Sorting passes 14:20:56 Now checking for duplicate satellites ... 14:20:56 Now writing satellite records ... 845 Satellite Records written 14:21:05 Press any key to continue ... In this example, 845 satellites were included in the 2-line elements file and the file was already sorted (no duplicate satellites were found). The complete process required 21 seconds; more time will be required if sorting must be performed and will depend upon the size of the file and the speed of your computer. In this case, the new file will be named "NASA085.TXT" and the original file will be renamed "NASA085.BAK". Press any key (except non-typing keys such as SHIFT or CTRL) to return to ORBITEL's Main Menu. Running Program ORBITEL in Batch Mode ------------------------------------- Like myself, the phrase "Batch Mode" is a holdover from earlier days when computer programs and their data were often submitted to be run "as a batch" and the user received the results (or sometimes just a series of error messages if the program was being debugged) some considerable time later. Today, the phrase usually means that the program executes in response to a series of instructions contained in a batch file, a file whose filetype is ".BAT". The phrase is also sometimes used to refer to the use of a program when all parameters required are entered on the command line (the characters following the program name typed at the DOS prompt). The use of ORBITEL from the DOS prompt is similar to the F4 selection when using the program interactively. The form of the command is: ORBITEL <filename> [options] where "<filename>" is the name of the 2-line elements file to process and [options] may be one or both of the following: /A Sorts output file in ASCENDING order of NORAD Numbers. The default is to sort in DESCENDING order of NORAD Number, placing Program ORBITEL Verify & Sort Orbital Elements Page i the most recent satellites (those with higher NORAD numbers) at the beginning of the output file. /N Does NOT remove TLE's with duplicate NORAD Numbers. This allows merged files and "LAST5" files to be sorted while retaining all TLE's. TLE's for the same satellite are grouped together in ascending order of Epoch Date. See example below. /O Adds orbit data to Line 0. The data is formatted as apogee in km followed by perigee in km (e.g. "364 x 355") beginning in column 50 of the line. NOTE: This is the letter OH not the digit zero! /U Unsorted output. The order of satellites in the output file is the same as the input file. Duplicate satellites will NOT be removed (as with the "/N" command line option). /X Always use file ORBITEL.XRF to replace satellite names on Line 0 if an entry is present. This permits users to substitute one satellite name for another or to correct an erroneous satellite name. For example, amateur radio enthusiasts may prefer to use "OSCAR-21" instead of "INFORMTR-1" for Norad #21575. This is easily done by including an entry " 21575 OSCAR-21" in file ORBITEL.XRF. Multiple options may be used: ORTIBEL NASA.LST /O/U will add apogee and perigee to Line 0 and generate unsorted output. By default, ORBITEL will remove all duplicate 2-line elements except the most recent. Using the "/N" command line option performs the same as the "NO Sort" option when used interactively and will process elements for the same satellite in ascending order of Epoch Date, as shown in the following example: Intelsat 6 1 20523U 90 21 A 92039.04552756 .00008522 00000-0 60373-3 0 6706 2 20523 28.3318 282.7030 0016740 137.2451 222.9377 15.02964371104940 Intelsat 6 1 20523U 90 21 A 92040.04160086 .00003959 00000-0 27372-3 0 6711 2 20523 28.3168 276.1581 0017876 144.3411 215.7910 15.02948478105097 Intelsat 6 1 20523U 90 21 A 92042.03371371 .00009772 00000-0 69437-3 0 6732 2 20523 28.3301 263.1098 0016731 168.2365 191.4355 15.02942356105392 Intelsat 6 1 20523U 90 21 A 92043.16265899 .00008101 00000-0 57361-3 0 6743 2 20523 28.3308 255.7126 0016553 180.5935 179.4275 15.02955973105565 Intelsat 6 1 20523U 90 21 A 92043.95950791 .00004471 00000-0 31092-3 0 6752 2 20523 28.3286 250.4967 0016496 189.4170 170.5602 15.02953000105688 Program ORBITEL Verify & Sort Orbital Elements Page i Using .LST and .SEL Key Files ----------------------------- ORBITEL may also use several "key files" when operated in the batch mode. These key files have filetypes ".LST" and ".SEL". If the filename specified has filetype ".LST", ORBITEL assumes that the file contains a list of files to process. For example, a list file called "NAVSTAR.LST" might include the following lines: * * Convert .DAT files for NAVSTAR data ... * NASA085.TXT INTEREST.DAT NAVIGATN.DAT THIRTY.DAT /NAVSTAR.TXT Files which contain 2-line elements are listed with a SPACE at the left and are sequentially read by ORBITEL. The output file is designaged with the "/" character at the left. Comment lines, lines which will be displayed but otherwise ignored, are designated with the "*" character at the left. By popular request, ORBITEL has been enhanced to allow the user to specify a list of satellites to include when used in the batch mode. When the filename specified in the command line has the filetype ".LST" and ORBITEL detects a file with the same filename and filetype ".SEL", that second file is interpreted as a list of NORAD Numbers to include in the output file; all other TLE's will be skipped. If "NAVSTAR.LST" is the list file and if select file "NAVSTAR.SEL" is found, the output file will contain 2-line elements only for those satellites whose NORAD numbers are included in the second file. File "NAVSTAR.SEL" might contain: 11054 1978 093A NAVSTAR 3/ 6 11783 1980 032A NAVSTAR 6/ 9 14189 1983 072A NAVSTAR 8/11 15039 1984 059A NAVSTAR 9/13 15271 1984 097A NAVSTAR 10/12 16129 1985 093A NAVSTAR 11/ 3 19802 1989 013A NAVSTAR 14/14 20061 1989 044A NAVSTAR 13/ 2 20185 1989 064A NAVSTAR 16/16 20302 1989 085A NAVSTAR 19/19 20361 1989 097A NAVSTAR 17/17 20452 1990 008A NAVSTAR 18/18 20533 1990 025A NAVSTAR 20/20 20724 1990 068A NAVSTAR 21/21 20830 1990 088A NAVSTAR 22/15 20959 1990 103A NAVSTAR 23/23 21552 1991 047A NAVSTAR 24/24 ORBITEL will read the numeric value at the left of each line in file "NAVSTAR.SEL" (ignoring the balance of the line), interpret it as a NORAD number, and include ONLY the resulting list of 2-line elements in the output file. In this case, assuming no "/N" command line option, the four specified source files will be loaded and only the most recent TLS's for Program ORBITEL Verify & Sort Orbital Elements Page i the 17 GPS NavStar satellites specified will be included in the output file "NAVSTAR.TXT". Beginning with Version 9303, the .SEL file may be specified as an entry within the .LST file and does not need to have the same file name. In addition, multiple .SEL and output files may be specified so that several sets of elements may be extracted from the same "master file". I use two files, SELECT.BAT and SELECT.LST to automatically generate several selected groups of elements. SELECT.BAT performs the primary task and also generates ZIP files for the selected sets of elements: ORBITEL SELECT.LST PKZIP -A -O ALLSAT ALLSAT.TXT PKZIP -A -O AMATEUR AMATEUR.TXT PKZIP -A -O GPS GPS.TXT PKZIP -A -O TVRO TVRO.TXT PKZIP -A -O VISUAL VISUAL.TXT PKZIP -A -O WEATHER WEATHER.TXT SELECT.LST is then used by ORBITEL to control the actual file reading, sorting, and selection processes: NASA.TXT <-- Note leading SPACE! GSFC.TXT <-- Note leading SPACE! /ALLSAT.TXT SAMATEUR.SEL /AMATEUR.TXT STVRO.SEL /TVRO.TXT SGPS.SEL /GPS.TXT SVISUAL.SEL /VISUAL.TXT SWEATHER.SEL /WEATHER.TXT Briefly, this process reads two 2-line elements files, NASA.TXT and GSFC.TXT, to form a composite sorted master file called ALLSAT.TXT. The same 2-line elements data are then used in succession to produce AMATEUR.TXT, TVRO.TXT, GPS.TXT, VISUAL.TXT, and WEATHER.TXT according to the contents of the respective .SEL files. When all .TXT files have been written, each .TXT file is then archived into a ZIP file using PKWARE's program PKZIP to minimize the file size. Sample files are included in the standard distribution package. Program ORBITEL Verify & Sort Orbital Elements Page i 2-Line Elements from Celestial BBS ---------------------------------- Major T.S. Kelso, USAF, operates the Celestial BBS in Fairborn, Ohio and regularly posts 2-line orbital elements in a variety of files. The satellite tracking community owes "TS" a considerable debt. His Celestial BBS was the first relaible electronic source of 2-line elements and, in addition, he has made information and program code available on the SGP4 and SDP4 orbital models which permit the data to be used to produce accurate satellite position predictions and has written several such programs himself. Major Kelso also teaches celestial mechanics and related subjects for the USAF. The following background information is posted on the Celestial BBS and is reproduced here for the information of users. - Two-Line Orbital Element Sets [26 January 1991] - Contents History Where To Find Data Frequency of Updates Format Description Source of Orbital Data NORAD Orbital Models Special Orbital Element Requests Satellite Frequencies Information on Specific Satellites Reposting Data Found Here ======= History ======= Effective January 1986, this system began posting the most recent two-line orbital element sets for several categories of satellites: Amateur Radio, Earth Resources, Manned Spacecraft, Navigation, Weather, and NASA's 30-Day Specials (which contain objects launched within the last 30 days and are often easy to spot visually). More specifically, these include the following satellites or satellite series: OSCAR, Radio Sputnik, UOSAT, Cosmos, LandSat, SeaSat 1, SPOT, Mir, Salyut 7, Soyuz, Progress, US Space Shuttle, NAVSTAR (GPS), Glonass, GOES, Meteor, and NOAA. ================== Where To Find Data ================== These elements will be maintained in ASCII format in the file BULLETIN.TXT which may be viewed with the 'B'ulletin command. This file is available for downloading from the System directory. The bulletins are also maintained in an archive, BULLETIN.ARC; this file is in the Satellite directory. Additional sets of elements may be found in files in the Satellite directory with a name of GROUP*.*. These files are groups of special distribution (see Special Orbital Element Requests). ==================== Program ORBITEL Verify & Sort Orbital Elements Page i Frequency of Updates ==================== The data provided on this system is generally updated three times a week. Updates are scheduled to be performed on Monday, Wednesday, and Friday evening, subject to the availability of the data. Difficulties in the process of obtaining the data result in frequent delays in this schedule (see Source of Orbital Data). ================== Format Description ================== Data for each satellite will consist of three lines in the following format (not including the two line "ruler): 1 2 3 4 5 6 123456789012345678901234567890123456789012345678901234567890123456789 AAAAAAAAAAA 1 NNNNNU NNNNNAAA NNNNN.NNNNNNNN +.NNNNNNNN +NNNNN-N +NNNNN-N N NNNNN 2 NNNNN NNN.NNNN NNN.NNNN NNNNNNN NNN.NNNN NNN.NNNN NN.NNNNNNNNNNNNNN Line 0 is an eleven-character name. Lines 1 and 2 are the standard Two-Line Orbital Element Set Format identical to that used by NASA and NORAD. The format description is: Line 1 Column Description 01-01 Line Number of Element Data 03-07 Satellite Number 10-11 International Designator (Last two digits of launch year) 12-14 International Designator (Launch number of the year) 15-17 International Designator (Piece of launch) 19-20 Epoch Year (Last two digits of year) 21-32 Epoch (Julian Day and fractional portion of the day) 34-43 First Time Derivative of the Mean Motion or Ballistic Coefficient (Depending of ephemeris type) 45-52 Second Time Derivative of Mean Motion (Blank if N/A) 54-61 BSTAR drag term if GP4 general perturbation theory was used. Otherwise, radiation pressure coefficient. 63-63 Ephemeris type 65-68 Element number 69-69 Check Sum (Modulo 10) (Letters, blanks, periods = 0; minus sign = 1; plus sign = 2) Line 2 Column Description 01-01 Line Number of Element Data 03-07 Satellite Number 09-16 Inclination [Degrees] 18-25 Right Ascension of the Ascending Node [Degrees] 27-33 Eccentricity (decimal point assumed) 35-42 Argument of Perigee [Degrees] 44-51 Mean Anomaly [Degrees] Program ORBITEL Verify & Sort Orbital Elements Page i 53-63 Mean Motion [Revs per day] 64-68 Revolution number at epoch [Revs] 69-69 Check Sum (Modulo 10) All other columns are blank or fixed. Example: NOAA 6 1 11416U 86 50.28438588 0.00000140 67960-4 0 5293 2 11416 98.5105 69.3305 0012788 63.2828 296.9658 14.24899292346978 Note that the International Designator fields are frequently blank. All epochs are UTC (Coordinated Universal Time). Satellites will be ordered by their Catalog (Satellite) Number. The data file will be updated as soon as possible after receipt of new element sets or whenever element sets are received for the space shuttle. Hopefully, this service will provide a central location for users to obtain this data in a timely manner and help eliminate the tedious process of entering data by hand directly from the NASA Prediction Bulletins. ====================== Source of Orbital Data ====================== Many people have inquired as to the original source of the data provided here, so I feel compelled to provide some background. Until 1990, *all* of the data available on this system came directly from the NASA Prediction Bulletins provided by NASA Goddard on *paper*. That means for over four years I entered all the data by hand using software specially designed to ensure the data was in the proper format and to perform maximal error checking. At the time I began this effort, satellite tracking by both professionals and amateurs was in its infancy and development and application was being severely hampered by the lack of data. After trying to convince NASA for several years to set up a system for electronic dissemination of orbital data, I decided to undertake the task myself. If you are interested in obtaining this data directly from NASA, it is free but it usually takes several weeks to have requests or changes processed. And there will be a mail delay between the time the data is updated and you receive it, depending on how far you are from NASA Goddard (Greenbelt, MD). Also, there are limitations on the number of packages that any one person can receive. The address is: National Aeronautics and Space Administration Code 513 Goddard Space Flight Center Greenbelt, MD 20771 Note that anything you can get from NASA on paper you can get here much sooner and in electronic form -- just follow the procedures for requesting data outlined below. Program ORBITEL Verify & Sort Orbital Elements Page i Beginning in 1990, I began obtaining data indirectly from NORAD for the entire catalog of objects on orbit. This data is provided on a daily basis in electronic form and it makes the actual process of updating the various sets of data provided here much simpler. However, the network of computer links required to transfer the data from NORAD to this system is somewhat complex and subject to frequent breakdowns. As a result, it often takes me several hours to get the data each time I perform an update. When I am unable to obtain the data from this source, I must fall back to the original method of entering the data by hand. The question which inevitably arises is, "How can I get the data from NORAD directly?" The simple answer is, "You can't." Obtaining this data is not a simple process of linking into a NORAD computer system and downloading the data. The data is sent through a network of about half a dozen computer links with at least one manual transfer along the way. Considering the amount of time I take each week to obtain this data, you should be thankful you don't have to repeat the process. The next question which arises is, "How can I obtain the entire database of two-line orbital element sets?" Again, I must answer, "You can't." There are several reasons for this restriction. First, there are some limitations on disseminating the entire catalog over which I have no control. In addition, the size of the file would be prohibitive. There are currently over 1500 users on this system and, as I'm sure you're aware, the system is frequently busy. If I could make the entire database available, even in compressed form, many people would want to download the entire database (many on a daily basis, whether they really needed it or not), making it nearly impossible to access the system for the majority of users. While I would like to have multiple 9600-bps lines to service this system to relieve this congestion, that goal is incompatible with the goal of keeping the system open to the maximum number of users (i.e., no access charges). ==================== NORAD Orbital Models ==================== You may be unaware of the special relationship of the two-line element sets provided here to the NORAD orbital models (SGP and SGP4) discussed in Spacetrack Report Number 3 (see SPACETRK.ZIP online in the Satellite directory). To get accurate predictions with the data provided here, you MUST use a program which uses these NORAD orbital models. Here's why. The two- line orbital element sets are generated using these models and they incorporate the various orbital perturbations (due to atmospheric drag, the "shape" of the earth's gravity field, lunar and solar gravitational effects, etc.) in a specific way that ONLY these models will properly interpret. One way to think about what's going on here is that you wouldn't expect to use one compression algorithm to compress data and another one to uncompress it and get good results! Most compression programs (PKZIP, PAK, etc.) check for these incompatibilities but most tracking programs don't. It is up to the user to ensure the proper orbital model is used. You may use any other orbital model you feel appropriate, but you should not expect to get very accurate results. Depending on the orbit of the satellite you Program ORBITEL Verify & Sort Orbital Elements Page i are working with, errors of many minutes may result. The good news is that after five years of making the NORAD orbital models and two-line element sets available, most tracking software (either commercial or public domain) now incorporate these orbital models. And there are many of the best such programs online this system in the Satellite directory (use the WHATSFOR option in the File Section and use "NORAD" or "SGP" as keywords to search on). ================================ Special Orbital Element Requests ================================ If you wish to receive elements for satellites other than those already included in the master list, please read the article on Special Orbital Element Requests. If you have any suggestions for improvements in these data dissemination procedures, please leave a message or comment for the SYSOP and I will get back to you. Please be aware that some plans are already underway for improvements; these plans are described in the article on the Celestial BBS Upgrade. ===================== Satellite Frequencies ===================== Oftentimes, users request lists of the frequencies used by the satellites contained in two-line element sets. While there are some lists online for amateur radio and weather satellites and the space shuttle (use the WHATSFOR option in the File Section and use "frequency" as a keyword to search on), it would be impossible for me to keep up with a list of frequencies for any large number of satellites. All satellites operate on a number of different frequencies and many of them change frequencies on a regular basis. Which frequencies you are interested in depends upon what you are trying to do. If you cannot find the information you need here, ask a specific question (e.g., What frequency does NOAA 11 transmit APT data on?) in a message addressed to ALL; that should get you started. I welcome the assistance of anyone willing to provide frequency information on satellites with which they are familiar; I will take whatever inputs I receive and compile them into a master listing. ================================== Information on Specific Satellites ================================== If you are interested in finding out more about some of the satellites for which two-line element sets are available here (such as size, weight, etc.), the following books are ideal references. Check your local bookstore or library for them. Nicholas L. Johnson, "The Soviet Year in Space 19xx", Teledyne Brown Engineering, 19xx. Giovanni Caprara, "The Complete Encyclopedia of Space Satellites", Portland House, 1986. Program ORBITEL Verify & Sort Orbital Elements Page i Phillip Clark, "The Soviet Manned Space Program", Orion Books, 1988. Kenneth Gatland, "The Illustrated Encyclopedia of Space Technology", Harmony Books, 1981. Douglas Hart, "The Encyclopedia of Soviet Spacecraft", Exeter Books, 1987. D.G. King-Hele, et al., "The RAE Table of Earth Satellites 1957--19xx", Wiley-Interscience, 19xx. Reginald Turnill, "Jane's Spaceflight Directory 19xx-xx", Jane's Publishing Company Limited, Fifth Edition, 19xx. Bill Yenne, "The Encyclopedia of US Spacecraft", Exeter Books, 1985. Bill Yenne, "The Pictorial History of World Spacecraft", Exeter Books, 1988. ========================= Reposting Data Found Here ========================= Finally, if you are reposting the two-line element set data provided by this system to another BBS, I ask that you download the file TLE-POST.HDR and add it to the beginning of your file before reposting. Doing so will ensure that the Celestial BBS gets proper credit for providing these elements in electronic form. - TS Kelso SYSOP, Celestial BBS Program ORBITEL Verify & Sort Orbital Elements Page i 1-Line Element Sets (OLE) ------------------------- The One Line Element (OLE) format is a somewhat abbreviated set of orbital data used by the Navy at the Naval Research Laboratory (NRL) and perhaps others. Some useful information which is included in the 2-Line Element format is omitted, such as the Revolution Number at Epoch. Other information, such as the International Designator, can often be obtained from other sources using the satellite number (NORAD catalog number). The only virtue to this format is its brevity, 60 characters for the single line of data, as shown in the following format (which does not include the "ruler" and the line beginning "nnnnn..."): 1 2 3 4 5 6 123456789012345678901234567890123456789012345678901234567890 nnnnnyydddffffffddddddiiiiiinnnnnneeeeeeaaaaaammmmmmxxxxxxxx 206399019071772000014705251829684400765901146334880715202450 Columns 1-5 NORAD catalog number Columns 6-7 year Columns 8-10 day number Columns 11-16 fraction of a day Columns 17-22 drag term (Implied decimal left) Columns 23-28 inclination (Implied decimal in the middle) Columns 29-34 ascending node (Implied decimal in the middle) Columns 35-40 eccentricity (Implied decimal left) Columns 41-46 argument of perigee (Implied decimal in the middle) Columns 47-52 mean anomaly (Implied decimal in the middle) Columns 53-60 mean motion (Implied decimal 2 from the left) Example: 206399019071772000014705251829684400765901146334880715202450 The following values are obtained: 20639 catalog number 90 year 190 day number .717720 fraction of a day .000147 drag term 52.518 inclination 296.844 ascending node .007659 eccentricity 011.463 argument of perigee 348.807 mean anomaly 15.202450 mean motion The input of elements in this form may be terminated by a line which contains a zero for the catalog number. One-Line Element format information courtesy Mike McCants. Program ORBITEL Verify & Sort Orbital Elements Page i ORBITEL Revision History ------------------------ Each released version of STSPLUS uses a four digit revision code such as 9333. 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 or to identify special versions. 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 STSPLUS through all of the minor twists and turns that usually accompany the evolution of such a complex 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. Version 9333 -- August, 1993 ---------------------------- -Added the "/X" command line option to force use of the cross reference file ORBITEL.XRF. This will set the satellite name on Line 0 to the corresponding satellite name entry in ORBITEL.XRF. This feature may be used to correct an erroneous satellite name or to substitute a different name for convenience. -The format for the GSFC OIG .DAT file has been changed to add a note (instead of no entry or obsolete TLEs) when no current 2-line elements are available for a satellite on the "pick list" for that .DAT file: SAT ID = 02639 Latest set = 1 02639 96001 A 93222.00000000 NO CURRENT ELEMENTS (blank line) ORBITEL now ignores these four lines and NO DATA is included in the output file for the specified satellite (NORAD #02639 in the example). Version 9329 -- July, 1993 -------------------------- -ORBITEL now supports NORAD Numbers greater than 32767. -Corrected a minor bug which produced the wrong error message ("File ORBITEL.XRF not found!") when there were more than 1800 entries in the cross reference file. The correct error message is now generated: "File ORBITEL.XRF has too many entries!" Version 9325 -- June, 1993 -------------------------- -Corrected a bug which caused the program to fail when using F2 to display orbital data a second time with the message "File ... not found!". Thanks to Bill Grobe for reporting the error. Program ORBITEL Verify & Sort Orbital Elements Page i Version 9316 -- April, 1993 ------------------------------ -Due to format changes in the Goddard OIG RBBS output format, spurious formfeed characters were introduced in the .DAT files and the resulting corrected. Version 9303 -- January, 1993 ----------------------------- -Added the "/U" command line option to disable sorting. The order of satellites in the output file is the same as in the input file. Duplicate satellites will NOT be removed. -Added the "/O" (letter OH, for Orbit data) command line option to cause ORBITEL to add the apogee and perigee in km to Line 0 of each 2-line element set starting at column 50. -Corrected a bug that caused the select function (when a .SEL file was used to select specific NORAD numbers) to fail unless the NORAD number was followed by a space. The trailing space and optional name are now not required and the .SEL file will be handled correctly whether or not these items are present. Thanks to Paul Traufler for the report! -Various cosmetic changes. -Documentation completely rewritten. Version 9214 -- April, 1992 --------------------------- -A bug was discovered in Version 9209 and before which caused the last set of 2-line elements to be omitted from the final file after sorting, etc. -The screen now displays the number of satellites in the current input file, rather than the cumulative total number of satellites read so far (as in prior versions). When in batch mode, the total number of satellites is now displayed following the output file name. Version 9209 -- February, 1992 ------------------------------ -Finally, after much nagging by friends and acquaintances, I have done some "serious work" on the sort algorithm. On my 386/20 and using files of 989 satellites total arranged in just about a "worst case" order, the sort time went from about 3.5 minutes to 1 minute. Version 9208 -- February, 1992 ------------------------------ -ORBITEL modified to accept the "/A" and "/N" command line switches in the batch mode. -By popular request, ORBITEL has been enhanced to allow the user to specify a list of satellites to include when used in the batch mode. Program ORBITEL Verify & Sort Orbital Elements Page i Version 9207 -- February, 1992 ------------------------------ -This version has been updated to process Joel Runes' Space Object Catalogs. The Catalog is divided into sections, each of which includes data on 2000 sequential NORAD Catalog numbers and TLE data when available. If ORBITEL is given a filename of "NORADCAT.nnn", all text and data will be removed and a new file, "NORADCAT.TXT" will be created containing only the TLE data. The original file will not be altered. NORADCAT files may also be included in batch files but note that since there are currently some 6300+ objects for which NORAD maintains TLE's, ORBITEL cannot make a single composite catalog; its present limit is 1800 TLE's. Version 9203 -- January, 1992 ----------------------------- -Thanks to a bug report by Tom Hayhurst, Version 9203 substitutes "0" for spaces in the DAY portion of the Epoch in Line 1. Thus, an Epoch such as "92 9.004999123" will be changed to "92009.004999123". The program does not sort/select properly at year changes when spaces are present. Version 9153 -- December, 1991 ------------------------------ -In accordance with TS Kelso and Celestial BBS, RPV Astronomy BBS is returning to checksum calculations for 2-line elements which count "+" as ZERO rather than as TWO. Let us hope that NASA and NORAD can manage to keep heading in the same direction on checksums for a while now. -Beginning on January 1, 1992, all 2-line elements posted on RPV ASTRONOMY BBS will be checked by this version of ORBITEL (or later) to verify checksums. Version 9148 -- November, 1991 ------------------------------ -Fixes a file naming problem. Sometimes the output file was left with a file type of ".$$$". Version 9147B -- November, 1991 ------------------------------- -This version fixes a minor bug that caused problems if the entries in the ".LST" file were not all upper case. Case no longer is significant. -The cross reference (.DAT files only) and sort times have been significantly improved. Still not Really Fast, but MUCH better ... -The running total for checksum errors is now shown as each input file is processed. The number of errors in a given file is the difference between the number shown and the number shown for the prior file. If no errors are detected, the message is omitted. Version 9147A -- November, 1991 ------------------------------- -Somehow an intermediate version of 9147 was released instead of the correct version. In that release, F2 and F3 did not work and the output file using the .LST batch file was incorrectly named. Version 9147A Program ORBITEL Verify & Sort Orbital Elements Page i corrects these problems. -Added file list capability to batch mode. If the file specified on the command line has filetype ".LST", ORBITEL assumes that it contains a list of input filenames and an output filename. Input filenames must be preceeded by a space and the output filename must be preceeded by the "/" character. All other lines in the file are considered comments and are echoed to the screen. -Renamed the cross--reference file to ORBITEL.XRF to avoid confusion with files of the same name from other programs. This file was inadvertently omitted from the Version 9144 distribution. Sorry ... Version 9144 -- October, 1992 ----------------------------- -Version 9144 will automatically add filetype ".TXT" if no filetype (or ".") is included in the filename. This applies to both interactive mode and batch mode operations. (This feature in Version 9144 was previously undocumented.) -Repairs a bug in Version 9134 that caused duplicate satellites to not always be removed depending upon the epoch time difference and the order of appearance in the file. The sort routine now correctly orders all duplicate satellites by epoch and retains only the most recent elements. -Adds a batch file capability. If a filename is included on the command line, the file will automatically be verified and rewritten as if the "W" command had been entered. Satellites are sorted in DESCENDING order. If the filetype entered automatically or with the "W" command is ".N2L", the original file will remain unmodified and a new file with filetype ".TXT" will be created which does NOT contain the beginning and ending comments (marked by lines "startn2l" and "endn2l" respectively); this permits automatic checking, sorting, and editing of Ted Molczan's NORAD 2-line element files. -ORBITEL is now able to process the 2-line format from the GSFC Orbital Information Group RBBS. If the filetype is ".DAT", the extraneous second text line is removed and the satellite ID number is compared against the file ORBITEL.XRF (provided by Paul Traufler and which must be in the same directory as ORBITEL) and replaced with the ASCII name if found; if the satellite ID number is NOT found in the SATNAMES.XRF file, the name in the output file is the satellite ID number. Note that this search and replace requires additional time for each satellite! The original file will remain unmodified and a new file with the same filename but filetype ".TXT" will be written. ORBITEL may now be used with the GSFG OIG "Last 5" element sets BUT only the most recent element set for each satellite will be written to the output file. A sample batch file I use with the GSFC files is included. Version 9134 ------------ -Removed excess spaces on the first line of each satellite. Users had complained that those spaces "confused" some tracking programs. Program ORBITEL Verify & Sort Orbital Elements Page i Version 9118 ------------ -Initial public release. Added sort feature which is still slow but improved. This is because I store the complete ASCII file in internal arrays AND because I use a quick and dirty "brute force" method to do the sorting. Improvements and suggestions are welcome.