[amsat-bb] Re: AMSAT TLE Question

Paul Williamson kb5mu at amsat.org
Mon May 7 10:17:27 PDT 2012

The nasabare.txt file is created from the 2-line elements bulletins by a little C program I wrote called NASAWASH. http://www.mustbeart.com/software/nasawash.html

NASAWASH was written to maximize the compatibility of its output. Its main purpose is to remove any text that isn't part of the two-line element sets, and generate a "clean" file that any program will accept as a completely valid stream of two-line element sets.

One of the compatibility issues, historically, has been treatment of "+" plus signs in the calculation of the checksum. Some programs would ignore plus signs, and others would add 2 to the checksum for each plus sign. These two methods are not compatible, except for element sets that don't contain any plus signs. That's why NASAWASH strips them out.

To create nasabare.txt on the AMSAT server, NASAWASH starts with the text of the AMSAT bulletin in 2-line format, exactly as emailed out to the KEPS mailing list. I notice that the plus signs are also missing from the elements in the KEPS bulletins, very likely for the same reason. I do not know what exact procedure Ray Hoad uses in generating the bulletins.

Did you encounter a compatibility problem with some program as a result of the missing plus signs? I'd be interested in more details.

73  -Paul
kb5mu at amsat.org

On May 7, 2012, at 7:01 AM, Thomas Doyle wrote:

> I notice that the AMSAT TLE data file
> (http://www.amsat.org/amsat/ftp/keps/current/nasabare.txt)
> uses what appears to be a "non-standard" format for the BSTAR drag
> value in some of the satellites (currently RS-30 HO-68 and SRMSAT).
> When the drag value is 0 the entry in the AMSAT files is 00000 0 rather than
> the more "standard" 00000+0. A drag value of 0 is certainly a curiosity in
> itself.
> I realize that we live in a world where a "standard" 8 foot 2 x 4 is 8 feet
> long but not
> 2 inches by 4 inches so there are possibly many "standards" for TLE data.
> I solved the problem I was having by switching to
> (http://www.celestrak.com/NORAD/elements/amateur.txt).
> I am still curious as to why the AMSAT file is different. Does AMSAT get
> their data
> from a different source or did AMSAT create their own standard for
> presenting the data.
> thanks,  W9KE tom ...
> _______________________________________________
> Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb

More information about the AMSAT-BB mailing list