Terra (formerly known as EOS/AM-1) is a joint Earth observing mission within NASA's ESE (Earth Science Enterprise) program between the United States, Japan, and Canada. The US provided the spacecraft, the launch, and three instruments developed by NASA (CERES, MISR, MODIS). Japan provided ASTER and Canada MOPITT. The Terra spacecraft is considered the flagship of NASA's EOS (Earth Observing Satellite) program. In February 1999, the EOS/AM-1 satellite was renamed by NASA to “Terra”.
INTRUMENTS
Advanced Spaceborne Thermal Emission and Reflection Radiometer
ASTER will provide the highest resolution images (15-90 m) of the Terra instruments. Images can be obtained in visible, near-infrared, shortwave-infrared, and thermal infrared wavelengths. ASTER consists of three separate telescope systems, each of which can be pointed by investigators at selected targets. By pointing to the same target twice, ASTER can acquire high-resolution stereo images. The instrument operates for a limited time during each orbit.
Clouds and the Earth’s Radiant Energy System
CERES consists of two broadband scanning radiometers that measure reflected sunlight, Earth-emitted thermal radiation, and total radiation. The CERES scanners operate continuously throughout the day and night portion of an orbit. The two instruments obtain a complete representation of radiation from any direction by sampling in different ways the reflected and emitted radiation.
Multi-angle Imaging SpectroRadiometer.
MISR is a new type of instrument designed to view the Earth with cameras pointed at nine different angles. As the instrument flies overhead, each region of the Earth’s surface is successively imaged by all nine cameras in four wavelengths. Global coverage is acquired about once every 9 days. MISR acquires 36 simultaneous images at up to 250 meters resolution, but only during the daylight portion of each orbit.
Moderate-Resolution Imaging Spectroradiometer.
MODIS will observe the entire surface of the Earth every 1-2 days with a whisk-broom scanning imaging radiometer. Its wide field of view (over 2000 km) will provide images of daylight-reflected solar radiation and day/night thermal emissions over the entire globe. MODIS will be able to see features as small as 250 m-1 km. Some of the 36 different wavelength regions that MODIS samples have never before been monitored from space. MODIS operates continuously.
Measurements of Pollution in The Troposphere
MOPITT will be the first scanning radiometer to measure from space carbon monoxide and methane concentration in the lower atmosphere. The instrument operates continuously, providing science data on both the day and night portions of an orbit.
SCIENCE OBJECTIVES
• To provide the first global and seasonal measurements of the Earth system, including such critical functions as biological productivity of the land and oceans, snow and ice, surface temperature, clouds, water vapor, and land cover
• To improve the ability to detect human impacts on the Earth system and climate, identify the “fingerprint” of human activity on climate, and predict climate change by using the new global observations in climate models;
• To help develop technologies for disaster prediction, characterization, and risk reduction from wildfires, volcanoes, floods, and droughts
• To start long-term monitoring of global climate change and environmental change.
