Space Surveillance Symposium

Allen Thomson (
Wed, 11 Oct 1995 04:29:38 -0700

I just obtained the unclassified proceedings* of the 1995 Space 
Surveillance Workshop which was held at MIT Lincoln Laboratory
last March, and found a few things which might be of interest
to Seesat regulars.

Several of the papers report preliminary results from a LEO orbital debris
detection campaign the U.S. Air Force Space Command sponsored in October 
and November of 1994. The campaign used a wide variety of sensors, from 
the NAVSPASUR VHF radar fence through UHF, L, C and X-band radars at a 
number of sites around the world, and finally to several kinds of optical 
sensors, including some  at Kwajalein called SuperRADOTs I hadn't known 
about.  (A colleague at work told me that the earlier RADOTs were 
installed when MIRV and penaid testing started to overwhelm the
ability of the existing radars to sort out incoming objects.)

A number of new results were obtained, of which the most interesting 
seem to be:

- There is an apparent absence of debris objects with rcs less than -30
dBsm at altitudes less than 800 km. This is in sharp disagreement with
current debris models, which predict an exponentially increasing 
population as the altitude decreases (down to some limit, of course -- 
I'd suppose 200 - 300 km). 

- There are more low-inclination objects than are reflected in the
NORAD catalogue; this is explained by the relative lack of Space 
Surveillance Network sensors near the equator.  A number of the 
objects are in seven-degree inclination, high-eccentricity orbits and 
are fairly large; apparently they are associated with Ariane launches 
into GTO from Kourou.  More high-eccentricity objects than expected were 
also found in the 20 to 30 inclination range used by the U.S. for GTOs.

- Three small (-20 to -30 dBsm) objects with eccentricities near 
0.7 and inclinations near 120 degrees were found.  These correspond to
no known spacecraft launches, although general considerations indicate
that Vandenberg AFB was probably the launch facility of origin.  Checks
with experienced surveillance system operators revealed that objects
such as these had been detected before, but not formally cataloged.

- Extensive observations were made of one object (UCT 81214), which
was optically bright but had a very low rcs at L-band (-45 dBsm at 
L band, just at the limit of system sensitivity) and totally escaped 
detection by a number of other sensitive radars.  It is suggested that
this may be only one member of a significantly large class of such 
objects and may help explain many previous unidentified optical 
satellite detections. 

Other interesting items were:

- A fast imaging photon-counting optical detection system in 
development at Los Alamos National Laboratory has undergone 
preliminary field trials and has performed as expected.  Ultimately, 
the developers hope to be able to detect and track LEO objects as faint
as visual magnitude 15 to 16.

- The FOX photometry and enhanced resolution imaging system has been
installed on the 50-cm satellite tracking telescope at the U.K. space
object identification facility at Herstmonceux.  It already has been
used during a European debris monitoring campaign and performed
bistatic photometry of geostationary satellites together with the
USAF Philips Laboratory site at Malabar, FL.

*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