Subject: Spysats: going higher?
From: thomsona@netcom.com (Allen Thomson)
Date: 1995/05/09
Message-Id: <thomsonaD8B2n5.yt@netcom.com>
Newsgroups: sci.space.policy
Various IC officials have made statements over the past two years
which seem to have strong implications for the future of US satellite
reconnaissance. Departing DCI Woolsey's valedictory statement to the
SSCI is typical:
"Pursuant to a plan that I put together in 1992, before I became
DCI, at the request of my predecessor, Bob Gates, we are in the
midst of cutting the number of reconnaissance satellites nearly
in half, and making even deeper cuts in ground stations."
World Threat Assessment Brief: Statement for the Record by R.
James Woolsey, Director of Central Intelligence, to the Senate
Select Committee on Intelligence, 10 January 1995, as prepared.
[Excerpt]
Other people, notably DNRO Jeffrey Harris and Keith Hall, DASDC3I,
have said similar things in interviews and congressional hearings. Just
what all this means in concrete terms has been something of a mystery,
but I believe that there may be some indication of the way things will
go in a recent publication by an IC official. The November 1994 issue
of Aerospace America contained an article ("The Space Business and
National Security, an Evolving Partnership") by DDCI Adm. William
Studeman which is remarkable for its frankness:
"Desert Storm did reveal some key shortfalls, the most
important of which can be tied to an inability to move data
with absolute efficiency and to provide the necessary total
coverage of the battlefield. A major one, of course, is the
inability of low-orbit imaging satellites to consistently dwell
or to acquire synoptic imagery in sufficient quantities to meet
intensive tactical demands. Similarly, because of bandwidth
demands of other architecture issues, we are plagued by
problems with the dissemination of imagery.
"In looking to the future we have kept these shortfalls in
mind and have developed strategies that should overcome them. A
main issue, though, is cost. We are carefully weighing the
tradeoffs that will allow us to provide -- in a resource
constrained environment -- collection assets that most
effectively address these deficiencies and other needs of
military leaders and policy makers."
If the governing requirements are to provide longer dwell and
synoptic imagery for battlefield use, then physics allows two
possible solutions: multiply the number of satellites in low orbit or
maintain a constellation of a few vehicles but raise their orbits
significantly. Since cost is a major constraint, the development of new
multisatellite systems or procurement of many more of the very expensive
current type seem to be ruled out, as Woolsey et al. said. So it looks
as if the future holds a migration of big spysats to altitudes higher
than the < 1000 km where they now seem to live. The NRO's continuing
requirement for heavy-lift vehicles is consistent with this idea.
As Kepler tells us, higher orbits are slower and provide longer
time-over-target. The additional time can be used to look at a limited
area repeatedly, or to scan a large field of view. If current spysats
have the ~3 meter aperture commonly quoted in the open literature, then
they could back off to ~5000 km altitude and still have a resolution of
1 meter, which is sufficient for most military and general
reconnaissance purposes. Transmitting less data per square meter of
target also sidesteps the bandwidth problem mentioned by Studeman.
I've run simulations for a number of high-altitude orbits to see
what kind of coverage they provide, and there are several promising
possibilities. Current favorites are ~5500 km x 500 km direct and
retrograde-sunsynchronous Molniya orbits that give high resolution at
perigee and long dwell at apogee. Argument of perigee could be adjusted
to suit the needs of the moment.
Going high has the added attraction of making satellites a bit less
vulnerable than those closer in. Five to ten Mm altitudes would
complicate the acquisition problem because the 1/r^4 dependence of
monostatic radar/lidar and 1/r^2 dependence of passive optics/IR make
the satellites harder to locate from the ground or LEO. Secondarily, an
ASAT weapon capable of reaching that high needs to be more expensive
than one designed to reach low altitudes. OTOH, the rapid advance and
spread of technology make these advantages uncertain and probably
transient, so a wise NRO would not count on them to keep its satellites
safe.
The problem of dissemination could be partially addressed by
providing direct downlinks to mobile user stations, rather than (or in
addition to) data relay through other satellites to a central processing
facility as is now apparently done. This approach also would make
possible a decrease in the number of fixed ground stations, consistent
with Woolsey's remarks.
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