ORBITEL Version 9846 Update Notes (3K Text File)
ORBITEL Version 9846 Program (150K ZIP File)
Current TLE data from RPV Astronomy BBS
ORBITEL Cross-Reference ORBITEL.XRF Updated monthly by Chief Hill
.XRF and .SEL Files for ORBITEL (Courtesy Chief Hill, Atlantic Beach, FL)
NOTE: These .XRF and .SEL files are updated monthly by Chief Hill.
Program ORBITEL is a utility program to verify, merge, and sort standard 2-line orbital elements files ("TLE files") such as those posted on my home page and and elsewhere. I use the program routinely to produce the TLEnnn.TXT and GSFCnnn.TXT files from "raw data" obtained from US Space Command via Col TS Kelso and the NASA Goddard Space Flight Center respectively. In both cases, the "raw data" consists of two or more files with differing names and sometimes non-standard format (OIG) which must be merged and then sorted to produce the final output file. Perhaps from force of 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.
e-mail: David H. Ransom, Jr. Back to Dave Ransom's Home Page