Landsat 4
Encyclopedia
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 imagery. Although the Landsat Program is managed by NASA
, data from Landsat 4 was collected and distributed by the USGS. Landsat 4 science operations ended December 14, 1993 when it lost the ability to transmit science data, far beyond its designed life expectancy of five years. The satellite
housekeeping telemetry and tracking continued to be maintained by NASA
until decommissioning June 15, 2001.
. It had a maximum 30 m resolution
. Shortly after launch, the satellite lost half of its solar power
and the ability to send science data directly to Earth, 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. Landsat 4 was able to resume science operations when the Tracking and Data Relay Satellite System
came on line, then was placed in standby in January 1986. Landsat 4 was brought back on line to provide international coverage in 1987, when Landsat 5 lost its TDRS link, and thus the ability to image areas beyond line of sight to a ground station, and continued to do so until it, too, lost its TDRS link in 1993, ending science data return.
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 spatial 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.
Landsat 5
was an identical clone of L4, a backup satellite and has survived over 25 years of active operation in space.
Landsat program
The Landsat program is the longest running enterprise for acquisition of satellite imagery of Earth. On July 26, 1972 the Earth Resources Technology Satellite was launched. This was eventually renamed to Landsat. The most recent, Landsat 7, was launched on April 15, 1999. The instruments on the...
. It was launched on July 16th, 1982, with the primary goal of providing a global archive of satellite imagery. Although the Landsat Program is managed by NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
, data from Landsat 4 was collected and distributed by the USGS. Landsat 4 science operations ended December 14, 1993 when it lost the ability to transmit science data, far beyond its designed life expectancy of five years. The satellite
Satellite
In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....
housekeeping telemetry and tracking continued to be maintained by NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
until decommissioning June 15, 2001.
Specifications
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 MapperThematic Mapper
One of the Earth observing sensors introduced in the Landsat program. A Thematic Mapper was first placed aboard Landsat 4 , and one is still operational aboard Landsat 5. TM sensors feature seven bands of image data most of which have 30 metre spatial resolution...
. It had a maximum 30 m resolution
Optical resolution
Optical resolution describes the ability of an imaging system to resolve detail in the object that is being imaged.An imaging system may have many individual components including a lens and recording and display components...
. Shortly after launch, the satellite lost half of its solar power
Solar power
Solar energy, radiant light and heat from the sun, has been harnessed by humans since ancient times using a range of ever-evolving technologies. Solar radiation, along with secondary solar-powered resources such as wind and wave power, hydroelectricity and biomass, account for most of the available...
and the ability to send science data directly to Earth, prompting fears the satellite would fail sooner than expected. This prompted the early launch of Landsat 5
Landsat 5
Landsat 5 is the fifth satellite of the Landsat program. It was launched on March 1, 1984, with the primary goal of providing a global archive of satellite photos. The Landsat Program is managed by USGS, and data from Landsat 5 is collected and distributed from the USGS's Center for Earth Resources...
, a satellite identical in specification to Landsat 4. Landsat 4 was able to resume science operations when the Tracking and Data Relay Satellite System
Tracking and Data Relay Satellite System
The Tracking and Data Relay Satellite System is a network of American communications satellites and ground stations used by NASA for space communications. The system was designed to replace an existing network of ground stations that had supported all of NASA's manned flight missions...
came on line, then was placed in standby in January 1986. Landsat 4 was brought back on line to provide international coverage in 1987, when Landsat 5 lost its TDRS link, and thus the ability to image areas beyond line of sight to a ground station, and continued to do so until it, too, lost its TDRS link in 1993, ending science data return.
Landsat 4 was the first satellite in the Landsat program to incorporate the TM (Thematic Mapper
Thematic Mapper
One of the Earth observing sensors introduced in the Landsat program. A Thematic Mapper was first placed aboard Landsat 4 , and one is still operational aboard Landsat 5. TM sensors feature seven bands of image data most of which have 30 metre spatial resolution...
) 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
Multispectral Scanner
The Multispectral Scanner is one of the Earth observing sensors introduced in the Landsat program. A Multispectral Scanner was placed aboard each of the first five Landsat satellites.-MSS Technical Specifications:...
.) 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 spatial 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.
Landsat 5
Landsat 5
Landsat 5 is the fifth satellite of the Landsat program. It was launched on March 1, 1984, with the primary goal of providing a global archive of satellite photos. The Landsat Program is managed by USGS, and data from Landsat 5 is collected and distributed from the USGS's Center for Earth Resources...
was an identical clone of L4, a backup satellite and has survived over 25 years of active operation in space.