Space Imagers - Sensors

There are many remote sensing systems in orbit. Currently UMAC relies on three main sensors as sources of imagery -- Landsat, MODIS, and ASTER.

Landsat

This image shows Namib Desert, taken in August, 2000. The color combination used assigns Red, Green and Blue to bands 4, 3 and 2.

Landsat satellites have been collecting images of the Earth's surface for more than thirty years since the first Landsat satellite launched in 1972. Instruments onboard the satellites have acquired millions of images of the Earth. These images provide a unique resource for people who work in agriculture, geology, forestry, regional planning, education, mapping, and global change research. UMAC has archived Landsat series data and currently stores more than 700 scenes covering five main UMAC states and part of Minnesota.

Landsat is a multispectral scanning radiometer and has provided nearly continuous coverage with a 16-day repeat cycle. The image data consists of seven spectral bands with a spatial resolution of 30 meters for most bands (1 through 5 and 7). Spatial resolution for the thermal infrared (band 6) during image acquisition is 120 meters, but the delivered data are resampled to 30 meter pixel size. The approximate scene size will be 170 x 183 kilometers (106 x 115 miles).

MODIS

This image shows phytoplankton bloom in Florida acquired on December 20 2003. The color combination used assigns Red, Green and Blue to bands 1, 4 and 3 in a true color representation.

MODIS (or Moderate Resolution Imaging Spectroradiometer) is a key instrument aboard the NASA Terra (EOS AM) and Aqua (EOS PM) satellites. Terra MODIS and Aqua MODIS are viewing the entire Earth's surface every 1 to 2 days. It has a viewing swath width of 2,330 km and views the entire surface of the Earth every one to two days, and ground target revisit cycle is 16 days. Its detectors measure 36 spectral bands between 0.405 and 14.385 µm, and it acquires data at three different spatial resolutions 250m, 500m, and 1,000m.

MODIS is ideal for monitoring large-scale changes in the biosphere. Almost every day over the entire globe, the sensor monitors changes on the land surface. The sensor especially observes the "green wave" that sweeps across continents as winter gives way to spring and vegetation blooms in response. UMAC’s DNGP uploads the 250m resolution MODIS data (red and NIR bands reflectance and NDVI) weekly basis.

ASTER

This ASTER image of Baltimore was acquired on April 4, 2000 and the color combination used assigns Red, Green and Blue to bands 3, 2 and 1 in a false-color infrared presentation.

ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) is an imaging instrument flying on NASA Terra, a satellite launched in December 1999 as part of NASA's Earth Observing System (EOS). ASTER is one of the five state-of-the-art instrument sensor systems on-board Terra with a unique combination of wide spectral coverage and high spatial resolution in the visible near-infrared through shortwave infrared to the thermal infrared regions. It was built by a consortium of Japanese government, industry, and research groups.

ASTER data have contributed to a wide array of global change-related application areas including vegetation and ecosystem dynamics, hazard monitoring, geology and soils, land surface climatology, hydrology, and land cover change.

ASTER imagery provides three different spatial resolutions; 15m in band 1-3 (Visible and NIR), 30m in band 4-9 (Short Wave InfraRed), 90m in band 10-14 (Thermal InfraRed) in 14 spectral channels. Spatial coverage of an ASTER scene is 60x60 km.

ASTER coverage mosaic created from about 80,000 cloud-free scenes.

The color combination used assigns Red, Green and Blue to bands 3, 2 and 1 in a false-color infrared presentation.

Animation courtesy: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team