Re: Gorizont 24

Björn Gimle (b_gimle@algonet.se)
Wed, 5 May 1999 21:05:29 +0200 

...
> observing conditions. However, both Gorizont 23 & Gorizont 24 are now well
> placed for European observers. For those observers who have never seen a
> geosynchronous satellites both of these objects are potentially visible in
> binoculars, flashing up to mag +5 at least. Gorizont 23 flash period is
> about 50s, whilst as Rob Matson indicates Gorizont 24 is flashing every 90s.
> 
> Here are recent elements for both of these objects;
> GORIZONT 23
> 1 21533U 91046A   99116.36469887  .00000017  00000-0  10000-3 0  1445
> 2 21533   4.5603  65.0425 0004945 103.1699 256.8504  0.98905113 22670
> GORIZONT 24
> 1 21759U 91074A   99113.45341774 -.00000018  00000-0  10000-3 0  8110
> 2 21759   4.2503  65.4330 0014683   2.6538 357.3166  0.98441951 27413
> 
Thanks to Jason's (and Rainer's and Gunnar's) alerts I finally saw my first
geosynch, with no more than 7*50 binoculars !

Of course it is no problem with magnitude 3.5 (my estimate) and good (SkyMap)
predictions. It is just that Rob's Superbird A predictions never coincided
with my weather, and I assumed other flashers were just as particular about
the time and location of visibility.

I observed 11 flashes over 19 periods. From my 'Synodic' plot of the absolute
times below ( 19 44.90 is 22:19:44.9 UT etc.) I get the period 50.487 seconds.
All points except two are within +- 0.12 sec of a centerline, one at +0.33 s
(late), and one 1.1 s early (!) - this is one I (thought I) saw at 1x power !

Using every (good) flash time instead of start-end reduces the error in
the period estimate.
Using absolute times means a single timing error does not affect the following
timing, and an error in reading or writing the time does not affect all
subsequent times.
Plotting the absolute times allows you to identify singular bad measurements
and ignore them, and estimate your timing precision.

0 19 44.90 0.00 -100.90 50.4870 781.00 "GORIZONT 23 21533 91-46A 1999-05-04 22:03:44.9 - 22:19:45.8  Mag +3.5 ?"
0 18 4.00 0.08 -50.20   
0 17 13.80 0.36 -252.70   
0 13 1.10 0.10 -151.40   
0 10 29.70 0.16 -100.90   
0 8 48.80 0.23 -101.20   
0 7 7.60 0.01 -50.40   
0 6 17.20 0.10 -51.60   
5 5 25.60 -1.02 -49.40   
0 4 36.20 0.07 -50.40   
0 3 45.80 0.16    


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