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Re: [APML] Satellite orbital taxonomy (was Satellite Tracking(was OK Whatthe He** is it??))
we used to take out the stars and other astronomical objects as noise. kept getting into trouble trying to convince people there was great astronomy and astronometry we were just discarding. just tons of data.
one thing is how much are you calling al elliptical motion in the satellite? the inclination on a geosynch is so small that theoretically you don't know the ascending RA point.
parking anything over a location without a geosynch orbit takes a lot of fuel (which is why we used geosynch except for a few other things which were further out).
and if you know the orbit, you know when its not there so you do the stuff you don't want observed during the times its somewhere else (which leads to frantic digging of holes, working for a few minutes then trying to fill in all the dirt...there's a reason for the Army dig a hole then fill it routine. gets you in the mindset for big holes in the ground.).
some Moly orbits had long dwell times over the US. it was a cheap way to keep a comm sat in a location without going to geosynch. they'd usually put several in same orbit so when one left station it had a backup. kinda similar to GPS.
once I project I was on came on line, they were pretty easy to keep track of. of course we killed Baker-nunn. ah well. progress, CCD over film.
I got even, worked on another project and proved film was better than CCDs.
hiding spy satellites isn't as much making it hard to find against a background. there were other limitations. decent star catelogues were incredibly helpful. take out stars, find what's left. its mainly a function of optical and CCD size. not your usual home grown stuff.
when I left that stuff, wanted to put more astronomy into the system. but don't know where its gone since then.
the usual limitations applied, seeing, background noise, weather, all the usual fun stuff astronomers have to deal with.
>>> rybskip@idcnet.com 5/22/02 9:07:00 PM >>>
Dear John,
On Wed, 22 May 2002 07:04:27 -0600, you said:
>Paul,
>
>> Since your photo was taken close to the ecliptic, note that
>> there is a class of _ecliptically_ synchronous spy satellites, one of
>> which may have been the cause of your problem. Whether or not these
>> are documented in recent literature would depend on the longevity of
>> databases of such objects.
>
>What do you mean by "ecliptically synchronous?"
I mean just that: they remain over nearly the same longitude
but stay within the _Ecliptic_ as it tracks north or south across
that longitude. One such satellite I tracked actually followed a
narrow, analemma-like pattern in the sky. I also tracked Russian
Molniya's which had highly elliptical -- but in no way geosynchronous
-- orbits. They were quite low and moved very rapidly across US
territory.
>Are you referring to
>satellites parked at the Earth's Lagrange points,
I don't think so, but I don't have the distance of the antisolar
Lagrange point from the center of the Earth and so don't know if a
satellite orbitting at that distance would yield a "geosynchronous"
track.
>or satellites in
>synchronous (24 hour) orbits at about 23.5 degrees inclination?
Definitely not. I described the orbit above.
>I can
>see no advantage to either orbit for a spy satellite - the Lagrange
>points are awfully far away, and the inclined 24 hour orbit doesn't keep
>the bird over a specific area.
Actually, there is; and that was why this location was such a
good one in which to park a spy satellite. To find a geosynchronous
satellite, you park a telescope at a specific altitude and azimuth,
don't move it and make lots of integrations. During those
integrations, stars will track through your field and possibly ruin
an exposure of a fixed target. The more stars, the better. Couple
trailing stars with a faint object moving orthogonally to the stars
and you create a spy satellite that is very difficult to find. Then
add orbit changes to this motion and you end up with a devilishly
difficult object to find. I know because I had to do it and
succeeded. But not without a very large (2.7 meter aperture)
telescope and not without knowing the orbit of the satellite. With
that same large telescope but without knowledge of the orbit, I would
not have had a prayer of finding this very faint object, even away
from the Milky Way plane. Note that a US quarter ($0.25 piece)
placed a geosynchronous distance will exhibit a maximum magnitude of
18. My object was fainter than that most of the time. However,
during maneuvering, the object could glint after sunset or before
sunrise just like the object in the photo under discussion.
>If you can tell me more about the
>orbital parameters you're talking about, I may be able to find out
>what's in that kind of orbit.
>
>> Note that a defunct such satellite may
>> have wandered away from the minimum in a specific tessoral harmonic
>> of the Earth's gravitational field where it would have been parked
>> years ago.
>
>This is a recurring problem with geostationary satellites (equatorial,
>synchronous orbits). The big gravity wells near the Indian Ocean and
>the Rockies tend to collect the drifters and the dead ones. However, I
>doubt that Jim's photo captured any drift - it's simply too short an
>exposure and the blob is tapered. My personal guess is that it's a
>rotating satellite body.
>
>> Only those who track space junk might know your culprit's
>> identity. And please correct me if I am wrong, but I believe NASA's
>> group who followed such objects optically were put out of business
>> recently by a NASA HQ costcutting measure.
>
>I don't know about NASA, but NORAD continues to track everything the
>Space Surveillance Network (SSN) can see. NORAD also provides collision
>avoidance assessment for all of NASAs flights, since they're the only
>folks who try to track everything. For deep space objects like those in
>synchronous orbits, they use variations of the Schmidt camera - first
>with film, then more recently with CCDs in the latest generation of
>sensors. Only a handful of radars can reach that far, but range data
>(not available from optical sensors) helps immensely in correcting the
>orbits of these objects. A lot of birds pay the ultimate price for
>collecting range data on deep space objects.
>
>Sincerely,
>Jon Kolb
>Adventures in Astrophotography
>http://home.datawest.net/jkolb/
>jkolb@datawest.net
Thanks,
Paul
--
Paul M. Rybski, Ph.D., Associate Professor and former Chair,
Dept. of Physics, and
Director, Whitewater Observatory
University of WI-Whitewater
Whitewater, WI 53190-1790
Office FAX: (414) 472-5633
Email address: rybskip@uww.edu
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