Re: high satellites with accelerating rotation

Jason Hatton (jason.hatton@etss.u-strasbg.fr)
Sat, 09 May 1998 14:05:29 +0000

Kurt Jonckheere wrote:

> >Gorizont 23 = 91- 46 A = 21533
> >Observations of the last months :              flashing period
> >91- 46 A 98-01-05 03:56:11.6 RM  306.2 0.5   6 51.04
> >91- 46 A 98-01-07 02:10      RGL       0.5  50 50.96  T=2547.9
> >91- 46 A 98-01-25 12:42      AB        0.2  30 50.667 T=1520.0, +-0.002
> >91- 46 A 98-01-26 12:45      AB        0.2  25 50.652 T=1266.3, +-0.002
> >91- 46 A 98-02-17 19:46:25.3 KJ        0.1  38 50.289 T=1911.0, mag max+5
> >91- 46 A 98-02-26 19:05      JPH 501.4 0.2  10 50.14
> >91- 46 A 98-03-18            MM                49.93
>  91- 46 A 98-05-04 20:54      KJ        0.1  28 49.908 T=1397.4

Last night (8-May-98, 21:10UT) I timed the flash period of Gorizont 23
to be 49.943sec (20 periods counted), so it looks like the period might
be increasing now. The flashes are quite bright (at least mag +5.7,
determined by comparison to field stars) & easily visible despite the
close proximity of the moon. Shortly after I made the timing Gorizont 23
passed only 1 deg. north of the moon, but was the flashes were still
easily visible in my 6" telescope with the moon at the edge of the
field! This set me thinking about another telecommunications satellite
now on its way to the moon, HGS-1 (AsiaSat 3).... 

Quoting Jonathan's Space Report
(http://hea-www.harvard.edu/QEDT/jcm/space/jsr/jsr.html):

"Final translunar injection on May 7 will lead to HGS-1 making a
circumlunar pass on May 13 followed by a return to geosynchronous
altitudes. The lunar flyby will be made with the satellite in
**spin-stabilized mode**, with the two main antennas deployed to give it
extra stability"

I know the odds are against it, but if HGS-1 is spinning & orientated
correctly it might flash brightly enough to be picked up visually in a
decent sized telescope. It is a large satellite with large solar panels.
The main problem is the close proximity to the near full moon & the
distance, 10x Geosynchronous distance = 100x (5 mag) fainter than a
comparable object in Geosync. orbit. However, one way maybe of detecting
it would be with a CCD; I've seen some extraordinary things acheived
with CCDs. A member of the Strasbourg astronomical association (SAFGA)
had suceeded in imaging faint galaxies taken with CCD's on moonlit
nights taken through thin cloud when the limiting visual magnitude was
+1! The raw image showed nothing, but image processing brought out an
image of faint star field with a galaxy. The other major problem is of
course knowing where to look - does anybody have really up to date
elsets (or predicted elsets) & will SDP4 based tracking programmes work
correctly for something on a lunar flyby?

Best wishes & clear skies,

Jason


Jason P Hatton
INSERM U311
ETS Strasbourg
67065 Strasbourg Cedex
France

48.538N / 7.731E / 143m