Hi David, KY7DR I suggest you to compare the 2 line NASA orbital data with the AMSAT Keplerian elements for the same day and you will get the answere to your questions.
Example for OSCAR-7 DECODE 2-LINE ELSETS WITH THE FOLLOWING KEY: 1 AAAAAU 00 0 0 BBBBB.BBBBBBBB .CCCCCCCC 00000-0 00000-0 0 DDDZ 2 AAAAA EEE.EEEE FFF.FFFF GGGGGGG HHH.HHHH III.IIII JJ.JJJJJJJJKKKKKZ KEY: A-CATALOGNUM B-EPOCHTIME C-DECAY D-ELSETNUM E-INCLINATION F-RAAN G-ECCENTRICITY H-ARGPERIGEE I-MNANOM J-MNMOTION K-ORBITNUM Z-CHECKSUM Two line NASA orbital data for orbit KKKKK or i.e. numbar 73100 AO-07 1 07530U 74089B 12256.61218065 -.00000027 00000-0 10000-3 0 4795 2 07530 101.4099 250.4681 0012001 109.6272 250.6089 12.53591141731001 AMSAT orbital data for the same Epoch revolution i. e. the same orbit numbar 73100 Satellite: AO-07 Catalog number: 07530 Epoch time: 12256.61218065 Element set: 479 Inclination: 101.4099 deg RA of node: 250.4681 deg Eccentricity: 0.0012001 Arg of perigee: 109.6272 deg Mean anomaly: 250.6089 deg Mean motion: 12.53591141 rev/day Decay rate: -2.7e-07 rev/day^2 Epoch rev: 73100 Checksum: 262 About your calculation: If the sign is plus like in +89689-4 your following calculation is correct: +89689-4 = 0.89689 * 10 ^-4 or 0.000089689 73" de i8CVS Domenico ----- Original Message ----- From: "David A. Rush" <[email protected]> To: <[email protected]> Sent: Thursday, September 20, 2012 2:19 AM Subject: [amsat-bb] Decoding Keps > I've been working on some code to decode the two-line Keplerian data > like the ARRL sends out weekly (with a thank-you to AMSAT-NA). > > A couple of the values are in a somewhat cryptic format, the "BSTAR" and > "second derivative of the mean motion". The strings tend to be either a > space or a + sign, five digits, usually a minus sign (but seen at least > once as a plus sign) and finally another digit, such as: > > +00000-0 > +11682-3 > 00000-0 > 30767-3 > 00000-0 > 00000+0 > +00000-0 > +89689-4 > > What I have found about this format is that it is "decimal assumed", and > examples suggest that +89689-4 = 0.89689 * 10 ^-4 or 0.000089689, if I > converted that correctly. > I'm guessing that the first character is the sign (+ or -) of the > number, where a space is assumed positive. I've only seen one example > of the 7th character being a plus (and all the digits were zero), so I > assume that + or - are valid values for the exponent. I guess the > format is fundamentally limited to an exponent between +9 and -9. > > Am I interpreting it correctly? Any other insight? > > David, ky7dr > _______________________________________________ > Sent via [email protected]. 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 _______________________________________________ Sent via [email protected]. 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
