{"id":7369,"date":"2012-06-05T09:00:09","date_gmt":"2012-06-05T14:00:09","guid":{"rendered":"https:\/\/esa.org\/esablog\/?p=7369"},"modified":"2012-06-05T09:00:09","modified_gmt":"2012-06-05T14:00:09","slug":"landsat-5-update-thematic-mapper-incommunicado","status":"publish","type":"post","link":"https:\/\/esa.org\/esablog\/2012\/06\/05\/landsat-5-update-thematic-mapper-incommunicado\/","title":{"rendered":"Landsat 5 update: Thematic Mapper incommunicado"},"content":{"rendered":"

End of routine acquisitions for the Thematic Mapper, secondary sensor is still sending data.<\/h2>\n

[update, March 2014: the Landsat 8 mission launched <\/a>successfully last year and the new satellite is sending great data back home. USGS decommissioned Landsat 5 in 2013.]<\/span><\/p>\n

By Liza Lester, ESA communications officer.<\/em><\/p>\n

\"landsat5<\/a>

Component problems or failures during Landsat 5\u2032s mission, specified by month\/year. Credit, NASA<\/a>.<\/em><\/p><\/div>\n

The US Geological Survey\u2019s Landsat 5 Thematic Mapper has been a faithful friend to ecologists. Recoding image data in seven bands covering visible, thermal, and infrared spectra, the satellite has shown us retreating glaciers, advancing wildfires, waxing and waning kelp forests, forest succession, and the ravages of bark beetle infestations.<\/p>\n

In November 2011, USGS shut down data transmissions for the duration of the northern hemisphere\u2019s winter<\/a> after the Thematic Mapper\u2019s transmitter began showing signs of trouble. USGS has not been able to resuscitate the ailing transmitter, and has ended routine data acquisitions from the Thematic Mapper. But is the program is<\/em> collecting data from a more limited, lower resolution instrument, the Multi-Spectral Scanner.<\/p>\n

The Thematic Mapper has been the workhorse instrument for routine image acquisitions on Landsat 5. The satellite\u2019s managers turned off the Multi-Spectral Scanner, an older design, in 1995. With the Thematic Mapper\u2019s data now out of reach, USGS switched the Multi-Spectral Scanner back on this spring and were gratified to see the instrument wake right up after slumbering more than fifteen years. The Multi-Spectral Scanner gathers data in green, red, and near infrared wavelengths, allowing us to distinguish vegetation and water boundaries, land formations, shallow water, and sediment-laden water. Check out the Landsat History Factsheet<\/a> for a comparison of sensor capabilities.<\/p>\n

This isn\u2019t the first transmitter failure. Landsat 5 is an old satellite, in orbit since 1984 and outliving several siblings, and its minders have worked around a number of equipment troubles. Its primary X-band<\/a> transmitter began having problems in 1987, just a few years after launch. Operations continued on the backup transmitter until 2008. After the backup failed, engineers flipped the switch on the primary transmitter, and it miraculously came back online. When USGS saw a familiar failure pattern developing last fall, they shut the instrument down hoping they could tweak things and get it going again, but the transmitter did not recover when they woke it in April.<\/p>\n

The Multi-Spectral Scanner (MSS) transmits on the S-band radio frequency<\/a> spectrum used for control of the satellite, and so is not affected by the Thematic Mapper\u2019s communication difficulties.<\/p>\n

USGS scientist Rachel Headley<\/a>, a geographer for the Landsat program, says it\u2019s fun to have the Multi-Spectral Scanner online again, although it\u2019s been so long since the sensor sent down data that the Landsat program has lost the capability to process it. USGS will not be releasing data until they can rebuild the necessary capacity and collect enough data for radiometric calibration<\/a>, which will make images consistent and comparable with other satellite spectra. That will not happen for many months, and certainly not before the end of the northern hemisphere\u2019s growing season.<\/p>\n

In the meantime, USGS is archiving the data. Though the Multi-Spectral Scanner is not as powerful as the Thematic Mapper, its archive could provide useful data continuity, particularly when merged with data from other missions. Maintaining the satellite\u2019s infrastructure does have a cost, however, and in the current, difficult budget environment, hard choices have to be made. USGS is discussing the value of continuing investment the Landsat 5 mission with stakeholders in the scientific community, and will decide its future soon.<\/p>\n

The latest Landsat scion, Landsat 8<\/a>, is in the final stages of construction and testing, and slated to launch in January or February of 2013.<\/p>\n

For updates on Landsat program, follow @USGSLandsat\u00a0 <\/a>on Twitter or check its Facebook <\/a>page.<\/p>\n

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Image: \u201cComponent problems or failures during Landsat 5\u2019s mission, specified by month\/year.\u201d\u00a0 NASA<\/a><\/p>\n

A sampling of recent ecological articles that have made use of Landsat data:<\/p>\n