USA 32 "Strobe"

Jason Hatton (
Mon, 13 Jul 1998 09:47:00 +0000

Hi All,
	I had a chance observation of an unusual flare off USA 32 (19460 /
88-078A) last night. At 22:13:30UT 12/7/98 I saw a series of bright,
strobe like flashes which lasted about 4-5 seconds before the satellite
faded down to a steady mag +4. The flashes were at least mag +0, if not
brighter which a frequency of perhaps 5Hz, resembling EGP in many
respects. Using the molczan elset I got a perfect ID with USA 32. Apart
from this brief strobe like flare the satellite appeared steady as I
followed it in binoculars for a couple of minutes. 
	Since this was the first time in nearly a month that I've been able to
get out & observe due to a combination of work, weather & travelling, I
made the most of the opportunity, eventually spending 5h outside
observing high altitude satellites using my 6" telescope! I think luck
was on my side, since I found most of the satellites I was looking for.
The nicest catch of the night was Hipparcus, a European star mapping
satellite  (89-062B / 20169) giving off sharp flashes, as bright as mag
+8 with a period of 8.4s. It was pretty obvious at the time I observed
it, but I failed to find it earlier in the night, so it's visibility
probably varies.     
		Finally, a short reminder that the flashing Geo sat Gorizont 23
(91-046A, Cat No. 21533) is now currently visible from Europe & will
remain visible for the next two weeks. 
	For those of you are new to the list Gorizont 23 is a Russian
communications satellite which is no longer functional in a near
geosynchronous orbit. What makes it interesting is that it brightly
flashes, up to mag +5, approximately once every 50 seconds as a result
of sunlight reflecting off surfaces on the satellite as it rotates. This
makes it one of the easiest geosynchronous satellites to observe. The
flashes which last about a second are easily visible even from an urban
observing site with small binoculars & it is within naked eye range from
a dark site. So if you've never seen a satellite in geosynchronous orbit
(ie. 40,000km distant) this is a good opportunity. Since Gorizont 23's
orbital period is slightly longer than 1 day it appears to slowly drift
westwards in the sky. So in two weeks time it will be visible from the

Happy observing & clear skies,


Jason P Hatton
ETS Strasbourg
B.P. 36
10 Rue Spielmann
67065 Strasbourg Cedex

48.538N / 7.731E / 143m