Decays of #22709, #22808 and #23580

From: Bjorn Gimle <Bjorn_Gimle_at_lector.kth.se>
Date: Wed, 31 May 1995 08:50:15 -0400
The bright EORSAT 1993-44A #22709 now has about a week's orbital life left.
It is just becoming visible after midnight, and will have passes before
and around midnight by the end of that week, when I expect it to decay.

The Spektr rocket, 23580, 1995-24B, will also decay in a few days, and
is visible in the mornings.

Here are Tuesday's last elsets on OIG:
Cosmos 2258      6.0  0.0  0.0  4.5
1 22709U 93044  A 95150.49626872  .00650455  00000-0  57790-3 0  4085
2 22709 065.0208 233.1918 0063510 241.0547 118.4114 16.07985839107754
Cosmos 2264      6.0  0.0  0.0  4.5
1 22808U 93060A   95149.19665816  .00073761  89907-5  12410-3 0  2309
2 22808  64.9818  97.2671 0089503 254.0150 105.1145 15.95494025 98617
Spektr rocket 23580
1 23580U 95024B   95150.19378276  .00506809  11738-4  31347-3 0   298
2 23580  51.6652 245.7872 0046333 114.4642 246.1192 16.14621336  1617

>#22808 still has its engine running, so it should stay up for at least
>two more weeks. It has evening visibility for a few more days.

Patrick Schmeer,extpasc@rz.uni-sb.de asks me :
>>How do you know that the engine of 22808 is still running?

#22808 belongs to a group of satellites called EORSATS, though I don't
know anything about them but their orbital behaviour, and their 6.0 m
diameter according to Molczan elsets, and that they are Russian.
They are quite bright and steady. While they are active, they are kept
very accurately at a mean motion of 15.520, in one or two planes,
120 degrees apart, and spaced 120 degrees from each other, and indeed
from an imaginary satellite with no atmospheric drag at all, within
common planes. When their useful life is over, they are brought
into an elliptic orbit with MM=15.82 to decay.

When #22585 was brought down, I noticed that the decay rate was very low.
Then, after about 45 days, it suddenly multiplied by a factor of
about six, to a normal value, and decayed a month later.
I have not made any historic studies yet, but this may have occurred
before. Here are NASA SatSit data for the ones I have studied.
Under the "Decayed" heading, I added the dates when they were brought
out of the 15.52 orbit, and when the drag rate increased :

1994-072A       23336   CIS        92.8    65.0      419       403  37.5332
COSMOS 2293   Launched (11/02/94)
1993-060A       22808   CIS        90.5    65.0      369       234  17.6791
COSMOS 2264   Launched (09/17/93)  Decayed [03/31?-06?/? -06?/?/95]
1993-044A       22709    USSR      92.8    65.0      417       400  44.9138
COSMOS 2258   Launched (07/07/93)  Decayed [02/27 -04/29 -06/5?/95]
1993-029A       22643    USSR      92.8    65.0      417       401  31.8618
COSMOS 2244   Launched (04/28/93)  Decayed [02/14 -02/14 -03/18/95]
1993-018A       22585    USSR      87.2    65.0      143       127  21.4165
COSMOS 2238   Launched (03/30/93)  Decayed [09/24 -11/09 -12/09/94]

#22643, #22709, and #22808 have behaved similarly, except that #22643
had no low-drag phase, and #22808 is still in the low-drag  phase.
When #22808 jumps to high drag, it may decay within 15 days, because
it now has an MM higher than the others had when the engine was shut off.

The force generated by the engine, though not enough for MM=15.82 and
higher, was quite sufficient at MM=15.52, and this should explain the
saw-tooth appearance of MM in the controlled orbit, not like the rather
infrequent burst that keep spy sats in a useful orbit.

I had intended to write an article with my supporting data and graphs,
for "Flash", but apparantly this won't be ready for press before the
decay of #22808.

>>For what date do you expect the decay of 22709?

I have contradicting evidence, so I am still very uncertain.
E.g. ndot2 has decreased since days 137-139, according to elsets !
Maybe the engine still has some residual power or fuel leaks ?
Some time between June 8 and June 12 is my best estimate, though
comparisons with the ones decayed already indicate June 4-5.

=========================================================
Bjorn_gimle@lector.kth.se == bjorn.gimle@duesenberg.se ==
== bjorn.gimle@online.dextel.se ;  59.22371 N, 18.22857 E
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Received on Wed May 31 1995 - 10:36:21 UTC

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