Source: LG-1999(02)-OOI-GSFC
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Landsat 7 PROGRAM
Landsat 7 is part of NASA's Earth Science Enterprise (ESE) program, a long term coordinated research effort dedicated to studying how our global environment is changing. It is the latest in a series of satellites that have provided a continuous set of calibrated Earth science data to users worldwide since the early 1970s. Landsat 7 will provide images of the land surface and surrounding coastal regions to national and international users conducting global change research, regional environmental change studies, national security activities and other civil and commercial purposes. Launch is scheduled for April 1999 from the Western Test Range at Vandenberg Air Force Base, Calif., on a Delta-II Expendable Launch Vehicle.
PROGRAM OBJECTIVES
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, extending the consistent 26-year record of the Earth's continental surfaces. Landsat 7 will image large areas of the sunlit Earth daily, revisiting the same areas every 16 days to refresh a global archive. Digital copies of all images in the archive will be available to users for the cost of fulfilling the request (estimated to be $600 or less per each 183 by 170 kru image).
APPLICATIONS
Landsat data are used by those who observe, monitor, characterize, study, map and manage the Earth's continental surfaces over time. Some examples of applications are: monitoring global deforestation, monitoring wildfire damage, estimating soil moisture and snow water equivalence, and monitoring flood, storm, earthquake and volcanic eruption damage. In addition, Landsat has been used to monitor strip mining reclamation, population changes in and around metropolitan areas, and to assess water quality in lakes.
SPACECRAFT AND INSTRUMENT
The Landsat 7 satellite consists of a spacecraft bus being provided under a NASA contract with Lockheed Martin Missiles and Space in Valley Forge, Pa., and the Enhanced Thematic Mapper Plus (ETM+) instrument being procured under a NASA contract with Raytheon (formerly Hughes) Santa Barbara Remote Sensing in Santa Barbara, California.
At launch, the satellite, including the instrument and fuel, will weigh approximately 4,800 pounds (2,200 kilograms). It is about 14 feet long (4.3 meters) and 9 feet (2.8 meters) in diameter. The ETM+ instrument will acquire data in the visible, near infrared, short-wave infrared, and thermal spectrums. The spatial resolution is 15 meters in the panchromatic band, 30 meters in the visible, near infrared, and short-wave infrared bands and 60 meters in the thermal infrared band. The instrument images the Earth in 115 mile (183 kilometer) swaths.
OPERATIONS
After being launched into a Sun-synchronous polar orbit, the satellite will use on-board propulsion to adjust its orbit to a circular altitude of 438 miles (705 kilometers) crossing the equator at approximately 10 a.m. on its southward track. This orbit will place Landsat 7 along the same ground track as previous Landsat satellites and Landsat 7 will fly over the same place on the globe every 16 days.
Following an initial 60 to 70 day checkout period, the satellite will begin normal operations. 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. NASA will continue to manage these day-to-day operations until October 1, 2000, when they will be turned over to U.S. Geological Survey (USGS).
U.S. data will be acquired primarily at the USGS's Earth Resources Observation Systems (EROS) Data Center (EDC) in Sioux Falls, S.D. Supporting ground stations in Alaska and Norway also will be used. All U.S. data will be processed, archived and distributed by EDC.
HISTORY
The first Landsat, originally called the Earth Resources Technology Satellite (ERTS-1), was developed and launched by NASA in July 1972. Subsequent launches occurred in January 1975 and March 1978. Meanwhile, a second generation of Landsat satellites was developed with an improved sensor, the Thematic Mapper. Landsat 4 was launched in July 1982. Landsat 5, launched in March 1984, is still providing images. As a result, there is a continuous set of Landsat images available from mid-1972 until the present. Landsat 6, a commercially managed and built spacecraft/instrument package, failed to reach orbit in October 1993.
MANAGEMENT
Landsat 7 was developed as a tri-agency program between the National Aeronautics and Space Administration (NASA), the National Ocean and Atmospheric Administration (NOAA), and the Department of Interior's U.S. Geological Survey (USGS). NASA is responsible for the development and launch of the satellite, and the development of the ground system. As the operator of the national meteorological satellite system, NOAA provided its operational expertise to the developers of the ground system. USGS is responsible for the operations and data archives.
As the operational era begins, Landsat 7 is transitioning to a dual-agency program between NASA and USGS. The transition and management have been governed by a joint management plan agreed to by the three agencies; future management will be govemed by a bilateral Memorandum of Understanding between NASA and USGS. The Landsat Project, located at Goddard Space Flight Center, 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 in Sioux Falls, South Dakota.
FOR THE CLASSROOM
When people want to know something about the Earth, they often take pictures of it from airplanes and spacecraft, such as Landsat, so they can get a perspective that is different from one on the ground. When aerial and satellite photographs are used to gather information about the Earth, the distance, range. and resolution of the pictures to be taken are determined by considering what data are required for a given investigation. For example, if you want to map forest cover, you do not need nor want to see each tree. In this activity, students will grasp the concept that being closer is not necessarily better or more informative. The optimal point of observation, or perspective, depends on what you want to find out.
Objectives: The students will be able to explain perspective, range, and resolution. They will also be able to explain how the optimal viewing zone varies with what it is they want to know.
Materials: A large sign, photograph or poster
metric ruler or measuring tape
chalk
magnifying glass
note pads to record discoveries
Procedure:
- Set up a large sign, photograph or poster on an outside wall of the school at eye level or in a location that allows you to view the item from far away such as a gymnasium or long hallway. Bring the class into view of the item from so far away that they cannot tell what it is.
- Have the students slowly approach the poster in small
groups or one at a time. Have them approach in stages such as 2
meters each time. At each stage have them write down what they
see and what they think is on the item posted. Have them
continue until they can identify it. At that point, they should
stop and mark the ground with chalk. They should then approach
the item posted until they are so close they can no longer tell
what it is. At this point, have them mark the ground with chalk
again. Finally, have the students move right up to the item
posted and examine some detail of it with a magnifying glass
and record what they see.
- Students then measure the two distances from the poster. These distances define the range or "window" within which their "remote sensors" (eyes) arecapable of gathering the most useful information.
Discussion:
- Your students should discuss what kinds of information they
observed from each of the various distances. They should try to
frame questions that can only be answered from close up, but
not from far away, vice-versa, and some questions that can be
answered from a medium distance.
- Explain that scientists gathering data by remote sensing do
the same kind of exercise that your students just did. They
figure out just how close or far away the camera needs to be to
give them the information they want.
- Discuss the types of data they think the Landsat 7 satellite will be able to provide to scientists.
Adapted with permission from the Aspen Global Change Institute's Ground Truth Studies Teacher Handbook - second edition
NOTE: Additional Landsat educational materials targeted for 5th through 8th grade students has been created at: http://ltpwww.gsfc.nasa.gov/landsat7/
For more information on Landsat, visit:
http://geo.arc.nasa.gov/sge/landsat/landsat.html