The Enhanced Thematic Mapper Plus (ETM Plus), the science instrument on Landsat-7, will continue a database of high- resolution Earth imagery begun in 1982 by the Landsat-4 thematic mapper. As changes occur on the Earth's surface due to natural or human-induced events, scientists will be able to use the archive of imagery from the Landsat missions to better understand the behavior of the global environment. Landsat images provide information meeting the significant and diverse needs of business, science, education, government and national security. Applications for Landsat-7 imagery will include agricultural crop planning, timber issues in the Northwest, and information about population change and water quality.

Landsat-7 will add to the global archive of sunlit, substantially cloud-free images of the Earth's land surfaces. The spacecraft contains several technological improvements over previous Landsat satellites and their instruments. These improvements include better instrument calibration and a solid- state data recorder capable of storing 100 individual ETM Plus Earth images. This capability will enable Landsat-7 to update a complete global view of the Earth's land surfaces seasonally, or approximately four times per year. The Landsat series has provided the longest record of the Earth's continental surfaces as seen from space.

"The launch delay of Landsat-7 was caused by a need for changes in the design of the electrical power-supply hardware for the spacecraft's instrument," said Phil Sabelhaus, Landsat-7 project manager at NASA's Goddard Space Flight Center, Greenbelt, MD. During instrument-level thermal vacuum tests beginning in December 1997, a power supply on the ETM Plus instrument failed twice. These technical challenges have been resolved and Landsat- 7 is on track for launch. "We're satisfied that our design concerns have been met, and we're ready for a springtime launch of the spacecraft."

Landsat 7 will continue the legacy of the first U.S. Earth Resources Technology Satellite (ERTS-1), launched in 1972, by building upon the only global data record captured from space.

The ETM Plus was designed and built by Raytheon (formerly Hughes) Santa Barbara Remote Sensing, Santa Barbara, CA. Lockheed Martin Missiles and Space built the Landsat-7 spacecraft, with integration of the instrument and spacecraft conducted at the company's facility in Valley Forge, PA.

NASA is developing in parallel to the Landsat-7 mission the next generation Landsat instrument and spacecraft technologies through the New Millennium technology demonstration program. This follow-on technology development effort will enable future measurements to be made by a sensor that is one-fourth the mass of the ETM Plus. A new sensor enabled by this development will use only 20 percent of the electrical power currently needed, while reducing the overall mission cost by 60 percent. The next generation Landsat flight demonstration is expected to launch in late 1999.

NASA intends to operate Landsat 7 and the flight demonstration spacecraft in the same orbit, but separated from each other by approximately one minute in distance. Such a flying formation will allow for observing the same area of Earth by both satellites, providing validation of the new imaging technologies being demonstrated. The advanced Landsat technology mission is intended to mitigate technological risk, improve future Landsat performance by a factor of four, and reduce overall mission development time by half.

Landsat is the central pillar of the national remote sensing capability. The Landsat 7 spacecraft was built to complement the research of NASA's Earth Science Enterprise, a long-term research program designed to study Earth's land, oceans, atmosphere, ice and life as a total integrated system. NASA's Goddard Space Flight Center manages the development of Landsat for the Earth Science Enterprise, NASA Headquarters, Washington, DC.

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