®®Landsat 7 was launched in 1999 from the Western Test Range by a Delta-II Expendable Launch Vehicle. At launch, the satellite weigh approximately 4,800 lbs (2200 kg). It is about 14 feet long (4.3 meters) and 9 feet (2.8 meters) in diameter. The Landsat 7 satellite consists of a spacecraft bus being provided under a NASA contract with Martin Marietta Astro Space in Valley Forge, PA and the Enhanced Thematic Mapper Plus (ETM+) instrument being procured under a NASA contract with Hughes Santa Barbara Research Center in Santa Barbara, CA.
A reaction control system is maintaining the orbit at an altitude of approximately 438 miles (705 km) with a sun-synchronous 98 degree inclination and a descending equatorial crossing time of 10:00 AM. The orbit is continuosly adjusted upon reaching orbit so that its 16 day repeat cycle coincides with the Landsat Worldwide Reference System. This orbit is maintained with periodic adjustments for the life of the mission. A three-axis attitude control subsystem stabilize the satellite and keep the instrument pointed toward Earth to within 0.05 degrees.
A silicon cell solar array, nickel hydrogen battery power subsystem will provide 1,550 watts of load power to the satellite. A communications subsystem will provide two-way communications with the ground. The command uplink and the housekeeping telemetry downlink will be via s-band while all the science data will be downlinked via x-band. A command and data handling subsystem will provide onboard commanding, data collection, processing and storage. A state-of-the-art solid state recorder capable of storing 380 gigabits of data (100 scenes) will be used to store selected scenes from around the world for playback over a U.S. ground station. In addition to stored data, real-time data from the ETM+ can be transmitted to cooperating international ground stations or to the U.S. ground station.