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
