NASA's Small Spacecraft Technology Initiative (SSTI) is a program designed to demonstrate technologies for reducing the cost and 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 greatly enhance the competitive posture of U.S. space system manufacturers in the global market.
The program was launched in June 1994 with the award of contracts to TRW Space & Electronics Group, Redondo Beach, California and CTA Incorporated, Rockville, Maryland. Under the contracts, two industry teams will build small (600 - 900 pound) satellites ("small-sats" or "lightsats") to be developed within two years, then launched into orbit and serviced for an additional year. The small spacecraft are designed to accommodate a wide range of mission requirements through use of standard hardware and software adapted to various applications. The initial satellites were named "Lewis" and "Clark" after the leaders of the early l9th century U.S. expedition to the Pacific northwest.
Both companies have extensive experience in building smallsats. TRW, one of the nation's major aerospace manufacturers, developed smallsat technology for a number of military programs, built several lightsats for NASA, and is currently building commercial lightsats. CTA is among the world leaders in manufacturing small satellites systems, having built, launched and operated 21 lightsats, with nine others in development. Both companies head teams of experienced aerospace manufacturers.
Shown at right, the TRW Lewis satellite will be a 870- pound spacecraft carrying three payloads for Earth observation, commercial remote sensing and astrophysics. Where typically payloads have represented 10 to 20 percent of a spacecraft's total weight, TRW has established a goal of 50 to 70 percent.
Lewis will incorporate more than 25 new spacecraft and payload technologies for providing superior performance while minimizing cost and schedule time, among them miniaturized cryocoolers, advanced composite materials, faster data processors, lightweight propellant tanks and smaller star trackers.
TRW is building one of the three Lewis payloads, a hyperspectral imager that will observe Earth in 384 narrow spectral bands (the NASA Landsat has seven bands). Although Lewis is a technology demonstration spacecraft, it will also operate as a commercial remote sensing system, supplying Earth resources data to a broad range of industry participants and schools.
The other payloads aboard Lewis are a broad area sensor, developed by Goddard Space Flight Center, that will provide spectrally resolved Earth imagery, and an extreme ultraviolet spectrometer, built by the University of California at Berkeley, to take images of the night sky and the cosmic background.
The CTA/Martin Marietta Clark satellite (lower right) will demonstrate 36 advanced technologies, among them a mini-star tracker, a low-cost Sun sensor, advanced composites, shape-memory mechanisms, room temperature x-ray detectors, image data compression, 3D imaging of atmospheric trace gases, and on-board data processing.
Clark will carry a modified commercial remote sensing imaging system and three science payloads. Principal focus will be on commercial remote sensing, which CTA sees as "the next frontier for domestic and international competition, with promise to become a multibillion dollar industry." Science research will include x-ray spectrometry, including solar flare measurements, cloud mapping and atmospheric tomography. CTA sums up its SSTI project as "a robust mission to deliver high value science, demonstrate multimission enabling technologies, use new design and qualification methods, and spawn commercially viable products in a two-year-to-flight profile."