EOS Terra Polar-Orbiting Satellite



Terra is a multi-national, multi-disciplinary mission involving partnerships with the aerospace agencies of Canada and Japan. Managed by NASA’s Goddard Space Flight Center, the mission also receives key contributions from the Jet Propulsion Laboratory and Langley Research Center. Terra is an important part of NASA’s Science Mission, helping us better understand and protect our home planet.

4.5-billion-year history is a study in change. Natural geological forces have been rearranging the surface features and climatic conditions of our planet since its beginning. Today, there is compelling scientific evidence that human activities have attained the magnitude of a geological force and are speeding up the rates of global changes. For example, carbon dioxide levels have risen 25 percent since the industrial revolution and about 40 percent of the world’s land surface has been transformed by humans. (Terra’s five main science objectives are discussed in detail in the fact sheets listed in the left-hand column of this page.)

Scientists don’t understand the cause-and-effect relationships among Earth's lands, oceans, and atmosphere well enough to predict what, if any, impacts these rapid changes will have on future climate conditions. Scientists need to make many measurements all over the world, over a long period of time, in order to assemble the information needed to construct accurate computer models that will enable them to forecast the causes and effects of climate change. The only feasible way to collect this information is through the use of space-based Earth “remote sensors” (instruments that can measure things like temperature from a distance). Consequently, NASA’s Earth Observing System has begun an international study of planet Earth that is comprised of three main components: 1) a series of satellites specially designed to study the complexities of global change; 2) an advanced computer network for processing, storing, and distributing data (called EOSDIS); and 3) teams of scientists all over the world who will study the data.

On February 24, 2000, Terra began collecting what will ultimately become a new, 15-year global data set on which to base scientific investigations about our complex home planet. Together with the entire fleet of EOS spacecraft, Terra is helping scientists unravel the mysteries of climate and environmental change. If you want to learn more about other EOS missions, visit the EOS Missions Page. If you want to learn about new EOS science results, visit the Earth Observatory.

Main Characteristics:

Launch date 18 December 1999
Spacecraft mass 5190 kg
Launcher  Atlas IIAS
Spaceport  Vandenberg Air Force Base
Average design lifetime  6 years
Orbital Parameters:
Orbit type Sun-synchronous, near-polar
Equatorial crossing time 10:30 a.m. ascending node
Average altitude 705 km
Semi-major axis 7085 km
Orbit period 99 minutes
Inclination 98°
Eccentricity 0.0015


On-board Equipment
Equipment Technical Parameters
Moderate Resolution Imaging Spectroradiometer (MODIS)
Polarization Sensitivity 2% from 0.43 m to 2.2 m and 45 scan
Swath 2300 km at 110° (±55°) from 705 km altitude
Spatial Resolution 13.5 km horizontal at nadir
Mass 229 kg

Duty Cycle 100%
Power 162.5 W (average), 225 W (peak)
Data Rate 6.2 Mbps (average), 10.5 Mbps (day), 3.2 Mbps (night)
Thermal Controllers Radiator
Thermal Operating Range 268°K ±5°K
Instrument Instantaneous FOV 250 m (2 bands), 500 m (5 bands), 1000 m (29 bands)
Physical Size 1.044 x 1.184 x 1.638 m
Measurement of Pollution in the Troposphere (MOPITT)
MOPITT is a nadir sounding instrument, which provides a horizontal resolution of 22 km, but introduces a number of challenges, such as the need for acurately characterizing the surface contribution to the signal.

For more information, see
the MOPITT page at www.ucar.edu.
The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER)
The Advanced Spaceborne Thermal Emission and Reflection Radiometer obtains high-resolution (15 to 90 square meters per pixel) images of the Earth in 14 different wavelengths of the electromagnetic spectrum, ranging from visible to thermal infrared light. Scientists use ASTER data to create detailed maps of land surface temperature, emissivity, reflectance, and elevation.

For more information, see
the ASTER web page
at NASA Jet Propulsion Laboratory.
Cloud's and the Earth's Radiant Energy System (CERES)
Three Channels in Each Radiometer Total radiance (0.3 to 100 µm); Shortwave (0.3 to 5 µm); Window (8 to 12 µm)
Swath Limb to limb
Spatial Resolution 20 km at nadir
Mass 50 kg per scanner
Duty Cycle 100%
Power 47 W (average) per scanner, 104 W (peak: biaxial mode) both scanners
Data Rate 10 kbps per scanner
Thermal Controllers Heaters, radiators
Thermal Operating Range 38±0.1°C (detectors)
Field of View (FOV) ±78° cross-track, 360° azimuth
Instrument Instantaneous FOV 14 mrad
Physical Size 60 x 60 x 57.6 cm/unit
Multi-angle Imaging Spectro-Radiometer (MISR)
MISR is a new type of instrument designed to address this need it will view the Earth with cameras pointed at nine different angles. One camera points toward nadir, and the others provide forward and aftward view angles, at the Earth's surface, of 26.1, 45.6, 60.0, and 70.5. As the instrument flies overhead, each region of the Earth's surface is successively imaged by all nine cameras in each of four wavelengths (blue, green, red, and near-infrared).

In addition to improving our understanding of the fate of sunlight in the Earth's environment, MISR data can distinguish different types of clouds, aerosol particles, and surfaces. Specifically, MISR will monitor the monthly, seasonal, and long-term trends in:
  • the amount and type of atmospheric aerosol particles, including those formed by natural sources and by human activities;
  • amount, types, and heights of clouds;
  • distribution of land surface cover, including vegetation canopy structure.

For more information, see
the MISR web page
at NASA Jet Propulsion Laboratory.