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January 19, 2023
Terra Constellation Exit
In April 2022, Terra began drifting to an earlier crossing time, reaching 10:15 am in October. In
mid-October, Terra lowered its orbit by 6 km. After "constellation exit" ASTER science
observations are continuing as before. Science observations will continue in concert with the
changing MLT. The major effect will be that the ASTER surface sampling pattern will no longer
be repeating every 16 days. However, sample locations will be reported with the data in the same
format as current data. The ASTER single pixel footprint size will decrease about 1% with the
lower orbit altitude, but will be maintained at 15m and 90m through re-sampling. We do not
expect these orbit changes to have significant impacts to ASTER data quality.
The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is an imaging
instrument onboard Terra, the flagship satellite of NASA's Earth Observing System
(EOS) launched in December 1999.
ASTER is a cooperative effort between NASA, Japan's Ministry of Economy, Trade
and Industry (METI), and Japan Space Systems
(J-spacesystems). ASTER data are used to create detailed maps of land surface temperature, reflectance,
and elevation. The coordinated system of EOS satellites, including Terra, is a major component
of NASA's Science Mission Directorate and the
Earth Science Division.
The goal of NASA Earth Science is to develop a scientific understanding of the Earth as an
integrated system, its response to change, and to better predict variability and trends in climate,
weather, and natural hazards.