Re: epoch; Progress M-33 deorbiting

Agapov Vladimir (
Wed, 12 Mar 1997 02:55:47 +0300

In message <>, Alan Pickup 
<> writes

>With a few exceptions, tles are for a point close to (but not exactly
>coincident with) a northbound equator crossing. I doubt if the object is
>under active observation at that position - rather I imagine the tle is
>an extrapolation from its observed motion at a later time on that rev.
>However, to get reasonable mean motion and drag terms, observations
>prior to the epoch must (usually) be included in the derivation of the
>tle. Of course someone (are you there Mike?) might suggest that some
>tles are "predicted", being based entirely on observations prior to the
>epoch. Does anyone have the answer?

Yes, some of TLEs are "predicted" indeed. I guess such TLEs produces for
some object which are hard to track due to their orbits and probably
due to SGP4/SDP4 theory that is using on tracking stations couldn't
be use to propagate correctly orbital motion for such satellites.
I know that such procedure is normal for 13901,19688,20413,21139,
22653,23331,23632,23686,23842 etc.
For example, currently you can found in OIG BBS
database TLEs for 13901 with epoch 97073.26759740, for 23632 - 97072.95002340,
for 20413 - 97071.56690600 despite of it is approx. 97071.0000000 now.

To the point, deorbiting of Progress M-33 is scheduled today, Mar 12.
Deorbit burn should take place at 02:35:00 UT, duration is 2 min 44.6 sec,
dV=87.90 m/s, current mass of Progress is 5592 kg.

Best regards,
   Vladimir Agapov.