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*Subject*: Re: [amsat-bb] TMSAT Status*From*: Roy Welch <rdwelch@xxxxxxxxxx>*Date*: Sat, 11 Jul 1998 14:51:50 +0000

I also had no trouble loading the keps here. Be sure that when you edit the message to get rid of the text that you delete the > character at the beginning of each line of the keps and that you don't leave a blank in it place. I have received a data carrier here just a few minutes ago on a low elevation pass to the east. The next pass will be better since this one was too weak to capture any data. I have found the frequency about 4 Khz higher here than I expected through out the pass. -- 73, Roy Internet: w0sl@amsat.org Home Page: http://home.swbell.net/rdwelch Chris Hill wrote: > > Hi Norm and All, > > I was able to load the two-line elements for TMSAT-1 into my satellite > program OK... > > In any case, I thought I'd respond to the "How is the modulo-10 checksum > calculated"; > > 1. Add up the value of the first 68 characters (numbers) in each line. > 2. Ignore non-numeric characters, except a minus sign ('-') counts as a 1 > (one). > 3. Divide the total by 10. > 4. The modulus is the remainder. > > For example, the line; > > 1 25395U 98043B 98191.87373682 -.00000045 00000-0 00000+0 0 24 > > adds to 134. > Dividing by 10 gives 13 (discard the 13), with a remainder of 4. Hence 134 > MOD 10 = 4. > > The simple check is that the 69th character in the line should be the > modulo-10 result as described above. In the example, the 69th character is > 4, hence the line is (probably) good. > > Here is a function taken from a Pascal program written by Dr T.S Kelso; > > +----------------------------------------------------------------------+ > Function Checksum_Good(line : line_data) : boolean; > var > i,checksum,check_digit : integer; > begin > checksum := 0; > for i := 1 to 68 do > case line[i] of > '0'..'9' : checksum := checksum + Ord(line[i]) - Ord('0'); > '-' : checksum := checksum + 1; > end; {case} > checksum := checksum mod 10; > check_digit := Ord(line[69]) - Ord('0'); > Checksum_Good := (checksum = check_digit); > end; {Function Checksums_Good} > +----------------------------------------------------------------------+ > > I used this routine in a little program I wrote, which allows the user to > edit some of the two-line elements in a text editor... my program then > calculates the mod-10 check digit and inserts it into each line, so that the > keps will check out OK in any program.... of course, the keps are false, > but it allows the user to experiment with some "what if's" like "what if a > LEO like KO-23 was in an essentially identical orbit to it's current one, > but inclined at zero degrees to the equator?". > > I've been meaning to clean it up a bit and describe it on a web page on the > Amsat site... if you would be interested in such a program, please let me know. > > 73 Chris VK6KCH > > p.s what version of InstantTrack are you running? > > At 19:29 11/07/98, you wrote: > >At 06:58 11/07/1998 +0100, you wrote: > >Snip..... > >>The following keps are accurate for tracking the spacecraft (Note that the > >>object number is not the final TMSAT object). > >> > >>TMSAT-1 > >>1 25395U 98043B 98191.87373682 -.00000045 00000-0 00000+0 0 24 > >>2 25395 98.7944 261.8948 0001516 6.1903 313.0257 14.22263117 96 > >>---- > > Ok, so when I load these into Instantrack I get the "mon 10 line checksum > >failed message. When compared to other elsets the checksum even looks > >wrong. Am I stupid and missing something... it has been a long day? > > > >BTW, how is the mod(ulus?)10 checksum calculated? I seem to recall having a > >similar problem with some Iridium elsets. > > > +-------------------------------------------------+ > | Chris Hill email : vk6kch@amsat.org | > | CRH Telnet PTY LTD A.C.N. 008 922 530 | > | Phone : +61 8 9354 8416 Fax : +61 8 9354 8826 | > +-------------------------------------------------+ > > ---- > Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA. > To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org ---- Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA. To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org

**References**:**Re: TMSAT Status***From:*Chris Hill

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