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Ocean Surface Topography from Space
Instrument Description

OSTM/Jason-2 is a follow to the Jason-1 and TOPEX/Poseidon missions and continues to provide high quality sea surface height data. The design for OSTM/Jason-2 and Jason-1 was based on the concept successfully validated by TOPEX/Poseidon. The three main instruments on Jason-2, the Poseidon-3 altimeter, the Advanced Microwave Radiometer (AMR), and the Global Positioning System Payload (GPSP), all trace their heritage to TOPEX/Poseidon.

OSTM/Jason-2 spacecraft
Jason-1 spacecraft


TOPEX/Poseidon spacecraft

510 kg


500 kg


2400 kg

TOPEX/Poseidon, Jason-1, and OSTM/Jason-2 all have the same suite of instruments. They are:

Altimeter(s) - measures range (the distance from the satellite to the Earth's surface), wave height and wind speed.

Radiometer - measures water vapor content in the atmosphere so that we can determine how it impacts radar signal propagation. Its measurements also can be used directly for studying other atmospheric phenomena, particularly rain.

DORIS - locates the satellite on orbit in real time. This information is essential for providing altimetry data in real time or near-real time.

Laser Retroreflector Array (LRA) - used to calibrate the other location systems on the satellite (DORIS, TRSR) with a very high degree of precision.

Global Positioning System (GPS) - supports precise orbit determination by the DORIS system. It also helps to improve gravity field models and provides data for satellite positioning accurate to about 50 meters and 50 nanoseconds.

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