re: Celestial optical transient or geosynch glint?

Philip Chien (
Sat, 20 Mar 1999 03:51:34 -0500 (Roland Vanderspek) said:

>(Sorry for the long-winded intro!).

hmm, obviously you haven't read many of my longer ramblings yet.

>The site of the telescope is California (121.87W, 37.88N, elevation
>maybe 500ft), and the transient was seen at RA=147.54, dec= *** -4.95 ***.
>When I saw the -4.95 degree declination, I thought "geosynchronous satellite".

>Mike McCants immediately picked up on a glaring omission in my previous email:
>The observation of the gamma-ray burst/geosynchronous satellite was on
>16 March at 9:41 UT.

Especially in the case of geosync satellites it helps to give the azimuth
and elevation (Yes, I know how to calculate it, but the easier you make it,
the easier it is to figure out what's up).  And if you can calculate the
sub-point longitude on the equator that's even more useful information.  I
can look at a geostationary longitude and most of the time know what
satellite's assigned to that location.  With only RA/Dec I've got a bit
more work to do.

>I'm also not very
>familiar with geosynchrous satellites and flashes from them:  with my
>instrument I saw steady geosynchronous satellites at about 8th magnitude,
>but that's a long way from 12.5.
>I was hoping someone on seesat could either give me a brief primer on the
>subject (is a flash at V=12.5 common?) or point me in the correct direction
>for reading up on the subject.

Geosync altitude objects can be lumped in to three categories - operational
satellites, non-operational satellites, and rocket bodies.

As a rule operational satellites are fairly steady objects.  They may have
an occasional sunlight glint but should not flash with any appreciable
rate.  (As a rule the solar panels are aimed directly towards the sun +/- a
couple of degrees so you'd have to be in an extremely unusual location to
have the right geometry for a bright flash.  Satellite size ranges from
fairly small Hughes HS-376 cylindrical spin-stabilized spacecraft to the
giant Milstar 1 series.  Most of these objects can be viewed in a backyard
telescope as stationary objects with the background stars moving behind.
Many have been spotted by Seesat viewers who can probably provide typical
magnitudes.  Photos and artist's renditions of most of these satellites are
available on the WWW at their manufacturers or owners web pages.

Non-operational satellites are raised in to a 'graveyard orbit' slightly
above geosync, so they precess 'backwards'.  They're shut off and either
enter a gentle tumble or some semi-stable attitude.  Obviously a satellite
which fails has no control and stays at geosync altitude until natural
pertubations push it out of the geo belt.  I doubt the smaller
spin-stabilized birds would flash much since they're cylindrical.  There
are several popular geo flashers and they all have a couple of things in
common - large flat solar arrays and spin rates which make them flash often
enough to be interesting.  Superbird A is probably the most popular.

Most western commercial satellites have built-in apogee systems and don't
result in additional rocket bodies at geo altitude.  However most U.S.
military satellites and Russian satellites use their launch vehicle to
perform the final apogee burns.  This includes anything launched by a
shuttle or Titan Intertial Upper Stage (TDRS, DSP, NRO geo birds), Titan
IV-Centaur (Milstar and assorted classified satellites) and any Proton geo
launch.  In these cases the final launch vehicle stage, remains in a near
geo orbit.  They quickly tumble since they don't have any attitude control.
I'm kind of surprised that nobody's reported spotting a Centaur (fairly
large and reflective) at geo altitude, however their elements are usually
impossible to get from OIG due to the fact that they're used to launch
classified payloads.  I believe several Proton upper stages have been

There's also a couple of geo satellites which eject their apogee stages
after they've finished their missions including the IABS (used to launch
DSCS-3 on an Atlas) and some weather satellite solid motors.  As a rule
these are fairly small objects.

Jonathan's Space Page has a list of geo objects and longitudes for most of

And just to toss a wrench in the works it's always possible that your
declination is just a coincidence and what you saw was a lower altitude
satellite which just happened to be passing across the geosync belt when
your observation took place.

And just to cover all bases, it's always possible that you happened to come
across a spaceship visiting Earth which forgot to turn on its stealth
shield for a couple of seconds ...

Philip Chien, KC4YER
Earth News
world (in)famous writer, science fiction fan, ham radio operator,
all-around nice guy, etc.