Landsat 4

Infobox Earth satellite
name = Landsat 4


launch_date = July 16, 1982
launch_vehicle = Delta 3920
launch_site = Vandenberg AFB
orbit_reference = WRS-2
orbit_type = sun-synchronous, near-polar
orbit_altitude = 705 km (438 mi)
orbit_inclination = 98.2°
orbit_repeat = 16 days
orbit_swath = 185 km (115 mi)
orbit_crossing = 9:45 AM +/- 15 minutes

Landsat 4 is the fourth satellite of the Landsat program. It was launched on July 16th, 1982, with the primary goal of providing a global archive of satellite photos. Although the Landsat Program is managed by NASA, data from Landsat 4 was collected and distributed by the USGS. Landsat 4 is no longer in operation, due to technical failure. It finally ceased transmission in 1993, far beyond its designed life expectancy of five years. The satellite orbit continues to be maintained by NASA.

pecifications

Landsat 4 had a maximum transmission bandwidth of 85 Mbit/s, and carried an updated Multi-Spectral Scanner used on previous Landsats, and a Thematic Mapper. It had a maximum 30 m resolution. Shortly after launch, the satellite lost half of its solar power, prompting fears the satellite would fail sooner than expected. This prompted the early launch of Landsat 5, a satellite identical in specification to Landsat 4.

It should be noted that Landsat 4 was the first satellite in the Landsat program to incorporate the TM (Thematic Mapper) sensor. The Landsat TM sensor is able to gather seven bands of data as opposed to the four bands of data collected from the MSS (Multispectral Scanner.) In addition to having three more bands of data to work with, scientists are able to view the TM data at a much higher resolution than with MSS. Bands 1-5 and 7 each have a spectral resolution of 30m while the MSS is only offered in 79m and 82m resolutions. Band 6 (which is a Thermal infrared band) has a maximum spatial resolution of 120m.

External links

* [http://landsat.gsfc.nasa.gov/about/L4_td.html NASA's Landsat 4 Website]