Landsat 5
Encyclopedia
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 Observation and Science
. On March 2nd 2009, Landsat 5 celebrated its 25th anniversary of operation, 22 years over its 3-year mission.
and the sun. The rotation of the solar array drive became sporadic, and the solar array was not able to provide the power needed to charge the batteries. Maintaining power to the batteries is critical to sustain proper operation of the spacecraft. The primary solar array drive failed under similar circumstances in January 2005. As a result of this situation, imaging operations were suspended. After a month-long investigation in December 2005 and testing in January 2006, new operating procedures were developed that will allow Landsat 5 to continue normal operations.
Data downlink was restored on January 7, 2010 after a test successfully managed to retrieve a picture over North America. This test exercised the only remaining Traveling Wave Tube Amplifier (TWTA). The remaining TWTA is in fact the primary TWTA that was in operation when Landsat 5 launched in 1984. After several issues in late 1986 and 1987, the primary TWTA was turned off and the secondary, or redundant
, TWTA had been used since. The USGS Flight Operations Team were able to apply lessons learned while operating the redundant TWTA to the primary TWTA for its first successful transmission in over 22 years.
of 705.3 km (438.3 mi). It takes some 16 days to scan the entire Earth
. The satellite is an identical copy of Landsat 4
and was originally intended as a backup: it therefore carries the same instruments, including the Thematic Mapper
and Multi-Spectral Scanner. The Multi-Spectral Scanner was powered down in 1995.
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 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 Observation and Science
Center for Earth Resources Observation and Science
The Center for Earth Resources Observation and Science is a United States Geological Survey data management, systems development, and research field center. It serves as the national archive of remotely sensed images of the Earth's land surface acquired by civilian satellites and aircraft...
. On March 2nd 2009, Landsat 5 celebrated its 25th anniversary of operation, 22 years over its 3-year mission.
Solar Array Drive Anomaly
On November 26, 2005, the back-up solar array drive on Landsat 5 began exhibiting unusual behavior. The solar array drive maintains the proper pointing angle between the solar arrayPhotovoltaic module
A solar panel is a packaged, connected assembly of solar cells, also known as photovoltaic cells...
and the sun. The rotation of the solar array drive became sporadic, and the solar array was not able to provide the power needed to charge the batteries. Maintaining power to the batteries is critical to sustain proper operation of the spacecraft. The primary solar array drive failed under similar circumstances in January 2005. As a result of this situation, imaging operations were suspended. After a month-long investigation in December 2005 and testing in January 2006, new operating procedures were developed that will allow Landsat 5 to continue normal operations.
Still sending data
In March 2009, Landsat 5 celebrated its 25 years in orbit and was still sending back data.Malfunction on August 13, 2009
On August 13, 2009, Landsat 5 tumbled out of control and power fell to a critical level due to an unknown event. Landsat 5 resumed nominal operation (battery savings mode) on August 17, 2009.Malfunction on December 18, 2009
On December 18, 2009, the transmitter on Landsat 5 experienced technical difficulties.Data downlink was restored on January 7, 2010 after a test successfully managed to retrieve a picture over North America. This test exercised the only remaining Traveling Wave Tube Amplifier (TWTA). The remaining TWTA is in fact the primary TWTA that was in operation when Landsat 5 launched in 1984. After several issues in late 1986 and 1987, the primary TWTA was turned off and the secondary, or redundant
Redundancy (engineering)
In engineering, redundancy is the duplication of critical components or functions of a system with the intention of increasing reliability of the system, usually in the case of a backup or fail-safe....
, TWTA had been used since. The USGS Flight Operations Team were able to apply lessons learned while operating the redundant TWTA to the primary TWTA for its first successful transmission in over 22 years.
Amplifier fluctuations in November 2011
On November 18, 2011, image acquisitions were suspended for a period of 90 days, due to fluctuations in the performance of a critical amplifier that is part of the satellite's transmission system. The satellite was said by the USGS to be nearing the end of its life, after more than 27 years in space.Specifications
Landsat 5 has significantly exceeded its designed life expectancy by over 22 years by 2009, and lasting 25 years total. It has a maximum transmission bandwidth of 85 Mbit/s. It was deployed at an altitudeAltitude
Altitude or height is defined based on the context in which it is used . As a general definition, altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The reference datum also often varies according to the context...
of 705.3 km (438.3 mi). It takes some 16 days to scan the entire Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
. The satellite is an identical copy of Landsat 4
Landsat 4
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...
and was originally intended as a backup: it therefore carries the same instruments, including the 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...
and Multi-Spectral Scanner. The Multi-Spectral Scanner was powered down in 1995.
External links
- Landsat NASA homepage
- Landsat.org Home Page
- Atlogis Maps and Atlogis Meta-Maps: Online-Viewer for Landsat 5 and Landsat 7 Natural Color Mosaic
- CEOS MIM Database Landsat 5 Entry