Re: USA 129 (spectacular glint) & QuickSat: questions

Bjoern Gimle (b_gimle@algonet.se)
Thu, 22 May 1997 21:49:31 +0200

Bill Krosney wrote:

>>Some questions:
>>
>>I felt pretty sure this was USA 129.  Has anyone observed it recently
>>such
>>that the above elements are indeed running about 3 minutes or more slow?
>>
>>Has anyone observed a bright glint from this sat before?
>>
I have seen similar glints from USA 86 for two years.

>>Is USA 129 in a sun-synchronous orbit, based on its inclination 
>>(>90 deg) and the fact that it repeated the same ground track almost
>>exactly 4 days later? 
>>
Yes, about 98 degrees - see the RAAN change by 0.985 degrees/day from
its 173.966 value in your set, like the Earth's motion around the Sun.

>>QuickSat actually selected USA 129 on my short list of sats brighter
>>than 3rd magnitude.  Although I ignored it because it predicted a 
>>magnitude 18!  I can understand the errorneous magnitude prediction
>>because there is no base magnitude for 24680 in the quicksat.mag file.
>>But I'm confused why it showed up in the short list.  Does QuickSat
>>ignore the magnitude filter if the satellite is not found in the 
>>magnitude file?
>>
The filter treats unknowns below a certain USSPACECOM number in one
way, above in another way :
"Line 7:  This line gives the 'cut-off' magnitude.
If the RCS value is unknown, then the intrinsic magnitude is assumed to be 
either 4.0 or 7.0 for this magnitude limit test.  For objects whose NORAD 
catalog number is less than 23328, an intrinsic magnitude of 7.0 is assumed.
For objects with a greater number, 4.0 is assumed."


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