Small Satellite Developments
NASA's Small Spacecraft Technology Initiative (SSTI) is a
program designed to demonstrate technologies for reducing the
cost and the time of getting civil and commercial space missions
from the drawing board to orbit. The program features new approaches
to satellite design and development that will not only significantly
lower cost but will also permit the builder to incorporate commercial
standards in the design and qualification process. Thus, the
program will serve NASA's needs by allowing more frequent space
missions within predictably lower budgets, and it will additionally
enhance the competitive posture of U.S. space system manufacturers
in the global market.
 Developed
by CTA, Incorporated, the Clark satellite is designed to demonstrate
technologies for a new family of satellites featuring reduced
cost and compressed development time.
The program was launched in 1994 with the awards of contracts
to two industry teams for development of "smallsats"
or "lightsats" in the 600-900 pound class. The small
satellites are designed to accommodate a wide range of missions
through use of standard hardware and software adapted to various
applications. The initial satellites are named "Clark"
and "Lewis" for the leaders of the 19th century U.S.
expedition to the Pacific northwest. Although the expedition
is invariably called "Lewis and Clark," the order is
reversed for the NASA program because Clark was scheduled for
the first launch. At Spinoff publication time in midyear
1996, Clark was targeted for November launch; Lewis was to follow
at yearend or early in 1997.
Clark is being developed by CTA, Incorporated, Rockville,
Maryland with Lockheed Martin Astronautics as principal subcontractor.
CTA is among the world leaders in manufacturing small space systems,
having built, launched and operated 21 lightsats, with several
others in development.
Clark is intended to demonstrate 36 advanced technologies,
among them image data compression, a mini star tracker, a low-cost
Sun sensor, advanced composite structures, room temperature x-ray
detectors, 3D imaging of atmospheric trace gases, and on-board
data processing.
Clark's sister satellite-Lewis-has an advanced remote sensing
imager that significantly broadens the range of Earth features
that can be analyzed. Both satellites will operate as commercial
remote sensing systems in addition to their NASA assignments
as technology demonstrators.
Although essentially a demonstrator of SSTI concepts, Clark
will also operate as a science and applications satellite with
three science payloads and a remote sensing imaging system. Principal
focus will be on commercial remote sensing which, CTA believes,
has promise of becoming a multibillion dollar industry. Science
research includes x-ray spectrometry, including atmospheric pollution
measurements, cloud detection and atmospheric tomography.
The Lewis satellite is being developed under the team leadership
of TRW Inc., Redondo Beach, California. One of the nation's largest
aerospace manufacturers, TRW developed smallsat technology for
a number of military programs and is currently building commercial
lightsats. Like Clark, Lewis is a technology demonstrator but
it will also carry science payloads and it will operate as a
pathfinder to stimulate the commercial market.
Lewis incorporates more than 25 new spacecraft and payload
technologies designed to provide superior performance while minimizing
cost and schedule time, among them miniaturized cryocoolers,
advanced composites, faster data processors, lightweight propellant
tanks and smaller star trackers.
A key feature of the Lewis spacecraft is a new Hyperspectral
Imager that will generate Earth imagery in 384 spectral bands
(the NASA-developed Landsat satellite has seven bands). The greater
capability of the imager will allow analysts to distinguish among
a much broader range of Earth features. The satellite will also
carry an extreme ultraviolet spectrometer, built by the University
of California at Berkeley, to take images of the night sky and
cosmic background.
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