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