The present paper present the EOS program, centerpiece of NASA's Earth Science program. It highligths the LANSAT program, and namely the LANDSAT-7 satellite, launched on April 15th, 1999, describing the technological innovations of the program, the management and data distribution policy.
The Earth Observing System (EOS), the centerpiece of NASA's Earth science program, is a suite of spacecraft and interdisciplinary science investigations dedicated to advancing our understanding of global change.
The flagship EOS satellite, Terra (formerly EOS AM-1), scheduled for launch end of 1999, will provide key measurements of the physical and radiative properties of clouds; air-land and air-sea exchanges of energy, carbon, and water; trace gases; and volcanoes. Flying in formation with Terra, Landsat 7 will make global high spatial resolution measurements of land surface and surrounding coastal regions.
Other upcoming EOS missions and instruments include QuickSCAT, to collect sea surface wind data; the Stratospheric Gas and Aerosol Experiment (SAGE III), to create global profiles of key atmospheric gases; and the Active Cavity Radiometer Irradiance Monitors (ACRIM) to measure the energy output of the Sun. The second of the major, multi-instrument EOS platforms, PM-1, is scheduled for launch in 2000.
Interdisciplinary research projects sponsored by EOS use specific Earth science data sets for a broader investigation into the function of Earth systems. Current EOS research spans a wide range of sciences, including atmospheric chemistry, hydrology, land use, and marine ecosystems.
The EOS program has been managed since 1990 by the Goddard Space Flight Center (GSFC) in Greenbelt, Md., for NASA's Office of Earth Science in Washington, D. C. Additional information on the program can be found on the EOS Project Science Office Web site (http://eospso.gsfc.nasa.gov).
Landsat is the United States' oldest land-surface observation satellite system. Although the program has scored numerous successes in scientific and resource-management applications, Landsat has had a tumultuous history of management and funding changes over its 26-year history. Landsat 7 marks a new direction in the program to reduce the costs of data and increase global coverage for use in global change research
NASA launched the first satellite in the Landsat series (originally called the Earth Resources Technology Satellites - ERTS) on July 23, 1972. The program was given the name Landsat in 1975. Efforts to move the Landsat program into the commercial sector began under the Carter Administration in 1979 and resulted in legislation passed in 1984 that charged the National Oceanic and Atmospheric Administration (NOAA) to transfer the program to the private sector. The Earth Observing Satellite Company (EOSAT) took over operation in 1985 and was given rights to market Landsat data. Landsat 5 was launched in March 1984 and is still returning images. Landsat 6, which was commercially built and managed, was destroyed after launch in October 1993.
With the passage of the Land Remote Sensing Policy Act in 1992, oversight of the Landsat program began to shift from the commercial sector to the federal government. In 1994, NASA was named the lead agency working with NOAA and the U. S. Geological Survey (USGS), and integrated Landsat 7 into its EOS program. The agency is responsible for the development and launch of the satellite, and the development of the ground system. As the operational era begins, Landsat 7 is transitioning to a dual-agency program between NASA and USGS. Future management will be governed by a joint agreement between the two agencies.
As part of NASA's EOS series of satellites, Landsat 7 will provide a unique suite of high-resolution observations of the terrestrial environment. The satellite will fly in near-formation with Terra, observing the same ground track just a few minutes apart. While other sensors onboard the Terra satellite, to be launched no earlier than November 1, will characterize daily changes at coarse resolution, Landsat will provide data at a finer resolution to allow for investigations of the causes of land-surface change.
Landsat 7 will gather remotely sensed images of land surface and coastal regions for global change research, regional environmental change studies, national security uses, and other civil and commercial purposes. It will capture and store in a U.S. archive global landmass data once per season. The Landsat 7 project is part of NASA's long term, coordinated research effort to study the Earth as a global environmental system.
Landsat 7 was launched on April 15 and began normal operations on June 29. All day-to-day operations will be turned over to the USGS in October of 2001. Right now, NASA controls flight operations, whereas USGS is responsible for other activities. The USGS/EDC (Earth Resources Observation Systems (EROS) Data Center, Sioux Falls, S. D.) will process, archive, and distribute all U.S. Landsat data; supporting ground stations in Alaska and Norway will also be used.
The Landsat Project, located at Goddard Space Flight Center (Greenbelt, Md.), manages Landsat development for NASA's Office of Earth Science in Washington, D.C. USGS operations will be performed at a Mission Operations Center at the Goddard Space Flight Center and at the EROS Data Center.
The Landsat Science Team, composed of 14 scientific investigators, was selected in 1996. These researchers are conducting a range of studies designed to exploit the characteristics of Landsat 7 for global change research.
The instrument on board Landsat 7 is the Enhanced Thematic Mapper Plus (ETM+). ETM+ is a passive sensor that measures solar radiation reflected or emitted by the Earth's surface. The instrument has eight bands sensitive to different wavelengths of visible and infrared radiation and has better resolution in the thermal infrared band than the Thematic Mapper (TM) instrument carried by Landsats 4 and 5. The instrument's calibration is good to within 5 percent, making the ETM+ far more accurate than its predecessors.
Continuity of data with previous Landsat missions is a fundamental goal of the Landsat program. To accomplish this, images will be taken that are consistent in terms of data acquisition format, geometry, spatial resolution, calibration, coverage characteristics, and spectral characteristics with previous Landsat data .
Revisiting the same areas every 16 days, Landsat 7 data will be used to build and periodically refresh a global archive of Sun-lit, essentially cloud-free images of the Earth's landmass. Landsat 7's commitment to collecting and archiving all scenes in the United States including Alaska and Hawaii is a significant change in the program. Daily commands will be sent to the spacecraft defining which images to record and when to downlink data either to U. S. or international ground stations.
With an upgraded data system on the ground, Landsat 7 will collect 250 scenes per day. The Landsat 7 receiving station will handle 4-5 times more data than the existing program's receiving station.
Processing, distributing, and archiving Landsat data will also be significantly improved. All Landsat 7 data received at the USGS EROS Data Center receiving station will be archived and available electronically within 24 hours and will be sold at cost. In addition to the main U.S. receiving station, several international ground stations will collect Landsat 7 data around the globe, archive it, and make it available through on-line Internet browsers. Steps are being taken to link the browsers and give users single point of entry to the network and easy access to Landsat catalog information.
U.S. Geological Survey - EROS Data Center - Sioux Falls, SD 57198