Subject: UCT 81214: Bright and stealthy
From: thomsona@netcom.com (Allen Thomson)
Date: 1995/10/11
Message-Id: <thomsonaDGAqwn.DBn@netcom.com>
Newsgroups: sci.space.policy,sci.space.tech,alt.war
A month or so ago we had a brief discussion of the
feasibility and utility of stealth in LEO. At the time I opined
that it might be worthwhile in tactical situations, but wouldn't
be a good idea if the aim were to protect satellites from
detection for long periods of time. The principal reason for
this, IMO, is the very wide range of sensor types and viewing
angles encountered by satellites in LEO and the fact that the
stealth technologies which have been revealed to date apparently
presuppose a known, fairly restricted set of "threat" sensors
and engagement geometries. Thus things designed to be stealthy
against one set of sensors might be detectable by other sensors
the designers hadn't known about or couldn't take into account
because of engineering constraints.
As it happens, a fairly concrete example of this has just come
to light (so to speak). Several papers in the proceedings of the
1995 Space Surveillance Workshop* describe preliminary results of
a orbital debris campaign sponsored by Space Command in late
1994. One of the interesting results concerned an object (UCT
81214) which was easily detected by a number of optical sensors
but was basically invisible to radars, some of them highly
sensitive range instrumentation radars, operating from 217 MHz
up to ca. 35 GHz. While 81214 probably wasn't intentionally
designed to have low rcs -- I'd guess it's a just a stray
fiberglass panel or something of the sort -- it nonetheless
illustrates the point that monostatic-radar-stealthy doesn't mean
optical-stealthy (and then there's IR, bistatic radar, lidar, etc).
"Of special interest was data collected on object 81214.
Initially detected by the ETS [Lincoln Lab optical sensors at
White Sands], this object has a bright optical signature but
appears very small to radar sensors, and may indicate the
presence of many more objects of this type...
"A considerable amount of data was collected on an interesting
object. Satellite 81214 appears moderately bright to optical
sensors, suggesting a large physical size. However, radar
tracking on this object indicates that it is quite small.
Millstone data at L-Band indicates a radar cross section of
approximately 0.00003 square meters, suggesting an object with a
small physical size. Several highly sensitive UHF radars have
been unable to track this object, however. Even the telescope
sensor at Anderson Peak, CA, that is normally not involved with
satellite tracking had no difficulty tracking this satellite.
The existence of this object and the data that has [sic] been
obtained lend credence to the theory that there is a population
of optically bright objects that appear quite small to a radar.
In fact, it is possible that many of the unknown objects
detected by optical sensors could fall into this area."
1994 Space Debris Campaign - Preliminary Results
Taft DeVere, SenCom Corp.
Tim Payne, SWC/AE
Capt. Gary Wilson, HQ AFSPC/DOYY
"[Kwajalein Missile Range] sensors participating in the 1994
Debris Campaign included ALTAIR (VHF, UHF), TRADEX (L- and S-
band), ALCOR (C-band) and MMW (Ka-band), and SuperRADOT visible
band optics...
"The most interesting optical track was on object 81214, which
was extremely bright to the SuperRADOTs, but was so small in
radar cross section as to be untrackable by the radars at the
1756 km point of closest approach."
Kwajalein Missile Range Contribution to the 1994 Debris Campaign
A. Gerber, G. Duff, and D. Izatt
MIT Lincoln Laboratory, Kwajalein Missile Range
*Proceedings of the 1995 Space Surveillance Workshop
28-30 March 1995
Lincoln Laboratory
Massachusetts Institute of Technology
Lexington, Massachusetts
K.P. Schwan, Editor
Project Report STK-235, Vol.1
(ESC-TR-95-022)
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