News | August 1, 2006

JPL's AMR Instrument on OSTM/Jason-2

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.

Photograph of some of the AMR team — **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.

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.

Jason-2_artists_concept_with_Jason-1_line_drawing_insert — 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 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

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.