Re: Question on #12986 Searches

Bjoern Gimle (
Thu, 15 May 1997 07:50:37 +0200

Ron wrote:

>This decaying object is in a 62 degree inclination orbit.
>The morning passes are moving to the south-southeast.  If the 
>object is early should I assume that it will be west of the 
>predicted path.  Also I assume that 1 degree per 4 minutes early 
>is the correct displacement.

Yes, this is correct. It is very slightly over 1 degree, since the
orbit progresses westward 1.2 + 0.98 degrees/day.

A larger effect to consider is the implied change of orbit parameters.
This morning (May 15 0530 UT) there were no new elsets, so you may
be working with (evolutions from) day 133.28 elset.
In two days, MM has increased by 0.8, and apogee decreased by 2200 km.
If this is 10% higher, its average MM has been 0.04 higher, and it has
made 0.08 orbits more. With a 200 min period, this makes it 16 min.
early. So, if you have a pass in the West, it will be four degrees
closer, but 220 km lower, since you are seeing it close to the apogee.

I hope my mental arithmetic is correct, and good luck!


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