RELEASE NO: 97-107

LEWIS SATELLITE READY TO DEMONSTRATE FINER SPECTRUM OF EARTH VIEWS

Outfitted with advanced technology Earth-imaging instruments and subsystems intended to push the state-of-the-art in scientific and commercial remote sensing, NASA's Lewis satellite is scheduled for launch at 2:51 a.m. EDT on August 10 from Vandenberg Air Force Base, CA.

Lewis features remote-sensing instruments designed to split up the spectrum of light energy reflected by Earth's land surfaces into as many as 384 distinct bands. In addition, Lewis carries the Ultraviolet Cosmic Background astrophysics instrument built by the University of California at Berkeley. The satellite was built by TRW Space & Electronics Group, Redondo Beach, CA, for launch aboard a Lockheed Martin Launch Vehicle (LMLV-1) under NASA's Small Spacecraft Technology Initiative.

"Lewis has proven to be a invaluable groundbreaker in our efforts to infuse fast-track procurement methods and industry-driven technology development into all of NASA's future spacecraft," said Samuel Venneri, Chief Technologist at NASA Headquarters in Washington. "This philosophy has since helped spawn the agency's New Millennium program and, more importantly, has fostered a mindset of innovation and partnership with industry across all of NASA's technology field centers."

The primary payload on Lewis consists of two complementary hyperspectral imaging radiometers. The 384-band Hyperspectral Imager (HSI) instrument built by TRW covers the spectral range from .4 microns to 2.5 microns. It is based on a conventional airborne spectro-radiometer design integrated with new advanced technology components, making it the first high-resolution hyperspectral imager to be flown in space. The HSI can resolve objects on the ground as small as 16 feet (five meters) in its panchromatic band and 100 feet (30 meters) in its hyperspectral bands.

The companion hyperspectral instrument on Lewis is called the Linear Etalon Imaging Spectral Array (LEISA). Built by NASA's Goddard Space Flight Center, Greenbelt, MD, it can "see" the Earth in 256 bands with 1,000-foot (300-meter) resolution, in the spectral region from 1.0 to 2.5 microns. LEISA's fundamentally new technology provides data in the same spectral bands as the HSI while offering "factors-of-ten" reductions in size, cost and design complexity as compared to conventional technology.

HSI and LEISA accomplish theoretically equivalent measurements using different approaches. The HSI takes a snapshot of a narrow "one-dimensional" stripe of the Earth and separates the incoming optical signal into its component spectral bands for a concurrent spectralobservation. It then uses the motion of the spacecraft over its ground track to build up the spatial image through 256 successive snapshots. In a criss-cross analogy, the new LEISA technology takes a "two-dimensional" snapshot of 256 adjacent stripes of the image, with each stripe viewed in a different spectral band. Using the motion of the spacecraft over the ground track, it then takes 256 successive snapshots, thus building up the complete spectral signature of each of the image stripes.

As a comparison, the primary imager on the Landsat-4 remote-sensing spacecraft views the Earth in just seven spectral bands with about 10 times lower resolution (although it has some thermal band capabilities beyond those of the HSI.) A key area of potential scientific and commercial interest in Lewis is the idea of "data fusion," where the unique new capabilities of Lewis are merged with the more mature Landsat data products to provide new insights.

"The sensors on Lewis will allow environmental scientists to discriminate between different types of vegetation, and determine their health, with a fine precision only hinted at by previous space- and aircraft-based measurements," said Dr. Diane Wickland, program scientist in NASA's Office of Mission to Planet Earth. "It also will enable much more accurate estimates of the run-off from spring snow melts, the distribution of surface minerals, and the composition of sedimentary discharges into coastal waters."

Potential commercial applications include pollutant monitoring, analysis of endangered species habitats, estimation of forest and agricultural productivity, soil resources and crop residue mapping and assessments of environmental impacts from energy pipelines, Wickland said. NASA's Stennis Space Center, Stennis, MS, will be the Agency's focal point for commercial applications and technical support on Lewis, and will help distribute and archive its data. Stennis also will work with TRW on spreading the results of Lewis into secondary school classrooms and will support validation of Lewis data via an aircraft-borne hyperspectral instrument flown on a NASA Learjet.

Another airborne imaging spectrometer instrument operated by NASA's Jet Propulsion Laboratory, Pasadena, CA, will support calibration and validation of measurements from Lewis and will help determine how the signals are changed when they pass through Earth's atmosphere.

Named for the 19th century U.S. explorer Meriwether Lewis, the mission incorporates approximately 40 new technologies and state-of-the-art components, including several developed at NASA Goddard. These new technologies include miniaturized cryocoolers, new composite material structural components with an integrated thermal and structural design, faster data processors, lightweight propellant tanks, miniaturized star trackers, and exploitation of the Global Positioning System (GPS) for space timekeeping, navigation and attitude control.

Lewis technologies contributed by NASA's Langley Research Center, Hampton, VA, include a Recorder Interface Module that provides both primary and back-up interfaces between the Lewis data recording system, the science instruments, the on-board computer and the communication subsystem. The Lewis Enhanced Attitude Control Experiment should lead to better future spacecraft attitude control systems that take into account the many disturbances a spacecraft experiences while in orbit, ensuring its science instruments remain accurately pointed. The Cloud and Feature Editing Experiment will assist the HSI by picking out areas of the Earth's surface that are covered by clouds, ensuring that only unobscured images of the Earth's surface are stored and transmitted to the ground for later analysis, doubling the useful capacity of the HSI image collection system.

The total cost to NASA of Lewis, including its launch vehicle and one year of orbital operations, is $64.8 million. Lewis and its partner remote-sensing technology demonstration mission Clark were selected by NASA for development in June 1994. The development of Clark has been paced by the availability of its commercially provided imager, and it is entering the final phases of construction. The earliest projected launch readiness date for Clark is early 1998.

The LMLV-1 booster will launch Lewis under the direction of TRW and Lockheed Martin from Space Launch Complex 6 (SLC 6) at Vandenberg. All checkout and launch-control equipment is housed in a Launch Vehicle Control Van, a 40-foot vehicle located near SLC 6.

Further technical details on the Lewis spacecraft and some color image files of the spacecraft being prepared for launch are available on the Internet at the following URL:

http://www.trw.com/seg/sats/SSTI.html

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