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Landsat 8 to continue the legacy

by Santosh Singh

No discussion about earth observation and Remote Sensing is complete without a mention of Landsat satellites. The Landsat program is the longest running endeavor for acquisition of satellite imagery of Earth. On July 23, 1972 the Earth Resources Technology Satellite , eventually renamed to Landsat, was launched. The most recent, Landsat 7 with ETM+ on board, was launched on April 15, 1999. Landsat 7 data has eight spectral bands with spatial resolutions ranging from 15 to 60 meters; the temporal resolution is 16 days. 

This satellite featured:

  •  a panchromatic band with 15m spatial resolution
  •  on-board, full aperture, 5% absolute radiometric calibration
  •  a thermal IR channel with 60m spatial resolution
  •  an on-board data recorder


Considered a triumph in satellite data calibration, the Landsat 7 mission went flawlessly until May 2003 when a hardware component called Scan Line Corrector failed resulting in wedge-shaped spaces of missing data on either side of Landsat 7’s images. In this SLC-off mode, the ETM+ still acquires approximately 75 percent of the data for any given scene. The gaps in data form alternating wedges that increase in width from the center to the edge of a scene. In order to make the data useful the gaps are filled using other SLC-off scenes or the scenes date prior to the failure.
So now what’s new in Landsat 8, also called Landsat Data Continuity Mission(LDCM), to be launched in February 2013? LDCM is a collaboration between NASA and the U.S. Geological Survey. It will provide moderate-resolution (15 m–100 m) measurements of the Earth’s terrestrial and polar regions in the visible, near-infrared, short wave infrared, and thermal infrared region.

Landsat Data Continuity Mission, an Artist’s impression. Courtesy NASA.

 

LDCM will provide continuity with the 38-year long Landsat land imaging data set. In addition to widespread routine use for land use planning and monitoring on regional to local scales, support of disaster response and evaluations, and water use monitoring, LDCM measurements will directly serve research in the focus areas of climate, carbon cycle, ecosystems, water cycle, biogeochemistry, and Earth surface/interior.
Landsat 8 features two sensors Operational Land Imager (OLI) and Thermal Infrared Sensor (TIRS). Below are the specifications of both the sensors:

Operational Land Imager (OLI):

Band # Spectral Region Wavelength Resolution
Band 1 Visible 0.433 – 0.453 µm 30 m
Band 2 Visible 0.450 – 0.515 µm 30 m
Band 3 Visible 0.525 – 0.600 µm 30 m
Band 4 Near-Infrared 0.630 – 0.680 µm 30 m
Band 5 Near-Infrared 0.845 – 0.885 µm 30 m
Band 6 SWIR 1 1.560 – 1.660 µm 30 m
Band 7 SWIR 2 2.100 – 2.300 µm 30 m
Band 8 Panchromatic 0.500 – 0.680 µm 15 m
Band 9 Cirrus 1.360 – 1.390 µm 30 m

Thermal Infrared Sensor (TIRS):

Band # Spectral Region Wavelength Resolution
Band 10 TIRS 1 10.3 – 11.3 µm 100 m
Band 11 TIRS 2 11.5 – 12.5 µm 100 m

The LDCM scene size will be 185-km-cross-track-by-180-km-along-track. The nominal spacecraft altitude will be 705 km. Cartographic accuracy of 12 m or better (including compensation for terrain effects) is expected of LDCM data products.

The LDCM spacecraft is scheduled to be launched on February 2013 aboard an Atlas V rocket from Space Launch Complex 3 at Vandenberg Air Force Base (VAFB), California. The launch will be the first Atlas V launch from VAFB.


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