Landsat Program History
Landsat 7 is the seventh in a series of land remote-sensing satellites. The Landsat satellites have been designed to provide a varied user community with timely visible and infrared imagery of the EarthÕs surface. The first Landsat satellite was launched in 1972. Landsat 2 and 3 (launched in 1975 and 1978 respectively) carried similar instrumentation to Landsat 1. In 1982 when Landsat 4 was launched it marked the first use of the Thematic Mapper (TM), a 7-band, mechanically scanned radiometer with 30 meter (m) ground resolution. In addition to using an updated instrument, Landsat 4 made use of the multimission modular spacecraft (MMS) to replace the Nimbus based spacecraft design of Landsats 1-3. Landsat 5, launched in 1984, was designed to be much like Landsat 4, containing only minor upgrades. Landsats 5 is still operational. Landsat 6 was lost shortly after launch in 1993.

Landsat 7
Landsat 7 represents a new generation of Landsat spacecraft. It carries the Enhanced Thematic Mapper Plus (ETM+), improving on the resolution and bandwidth obtained by past and current Landsat missions. Also, unlike Landsats 1-5 which were driven by user requests, Landsat 7 is operated largely as a survey mission, continually refreshing an existing Landsat database. Users of Landsat 7 will be able to obtain their desired data from a continuously updated archive rather than requesting the imaging of specific scenes on an as needed basis. This archive will be available to users for browsing and ordering of products. In keeping with past Landsat missions, international cooperators are able to pay a fee in order to receive science data directly from the spacecraft for their own use.

Landsat 7 was designed to have a lifetime of at least five years.

The National Aeronautics and Space Administration (NASA) was responsible for development of the Landsat 7 spacecraft and ground system. After launch, responsibility for spacecraft operations was transfered to the USGS. In addition, USGS is also responsible for the capture, processing, and archiving of all instrument and necessary ancillary data. USGS will also provide customer services to the user community.

Landsat 7 is operated from a control center located at Goddard Space Flight Center, a NASA facility in Greenbelt Maryland. Science data is captured and processed at the EROS Data Center, a USGS facility in Sioux Falls, South Dakota. Ground Sites in Sioux Falls, and Alice Springs Austrailia are used as downlink sites for all mission data. The NASA Telemtry Data Relay Satellites (TDRS) are also used to support the mission operations.

Launch and Orbit
Landsat 7 launched in April 1999 on a Delta II 7920-10 expendable launch vehicle from the Vandenburg Air Force Base, CA.

The Landsat 7 orbit has been chosen, and is maintained so that the groundtrack follows the well established Worldwide Reference System (WRS). The WRS is a series of "Paths" and "Rows" that are analogous to latitude and longitude and facilitate identification of individual images. This orbit gives the spacecraft near full Earth coverage and allows it to pass over any point on the Earth every 16 days. Although they vary slightly due to drag and other environmental factors, approximate orbital elements are as follows: