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Ocean Surface Topography from Space
JPL's AMR Instrument on OSTM/Jason-2
August 01, 2006

The Ocean Surface Topography Mission on board the Jason-2 satellite (OSTM/Jason-2) slated to launch
in June 2008 will continue the long-term collection of sea-surface height data, which began with
TOPEX/Poseidon in 1992 and continued with Jason-1, launched in 2001.

Some of the AMR team members.
Some of the AMR team: Standing, L to R: Orland Harrison, Reza Mohazeb, Andy Stone, Pete Kobzeff, Kobie Boykins, Ami Kitiyakara, Eric Olds, Bobbie Woo, Carolina Flores-Helizon; Kneeling, L to R: Ali Pourangi, Jim Aragon, Rudy Vargas
OSTM/Jason-2, like its predecessors, will include a suite of instruments allowing it to make extremely
accurate measurements of sea-surface height. The primary instrument for measuring sea-surface height
is the Poseidon-3 radar altimeter. The altimeter transmits microwave signals from the satellite to the
surface and measures the time it takes for the signals to return. Knowing the speed of transmission
and the time it takes to return, gives the distance to the surface. Since water vapor delays the signal's
return speed, to achieve an accurate measure of this distance, you have to remove the effects of water in
the atmosphere.

The Advanced Microwave Radiometer or AMR is the instrument on board the satellite that measures water vapor.
JPL has responsibility for the design and integration of this critical instrument. An excellent team of highly
trained and dedicated engineers is working on the AMR right here at JPL.

artists concept of Jason-2, with an insert of a line drawing of Jason-1.
Artist's concept of the Jason-2 satellite. The insert is a line drawing of the Jason-1 satellite showing the position of the Jason Microwave Radiometer. The AMR will be located in a similar position on the Jason-2 satellite.
The OSTM/Jason-2 AMR is an enhanced version of the Jason Microwave Radiometer (JMR). The instrument measures
total water vapor along the path viewed by the altimeter. In addition to measuring total water vapor, it is
used for range correction and to measure brightness temperatures. Resembling the JMR, the AMR combines the
measurements acquired at three different frequencies, and from this, scientists can extract the water
vapor signal.

The AMR consists of two subsystems: the Electronics Structure Assembly (ESA) and the Reflector
Structure Assembly (RSA). The ESA is developed by JPL, while the RSA is developed by ATK Space
Systems in San Diego.

Even when in the process of being built the AMR must go through a barrage of tests including
instrument calibration. The AMR calibration target shown below is not part of the instrument
but is instead being used for radiometric calibration of AMR in the thermal vacuum chamber.

AMR Electronics Structure Assembly AMR Reflector Structure Assembly AMR calibration target
AMR Electronics Structure Assembly   AMR Reflector Structure Assembly   AMR calibration target

The AMR is one of several instruments making up the OSTM/Jason-2 payload. We will continue to
watch its progress and that of the other spacecraft instruments as we move closer to launch.

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