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TOPEX/Poseidon: Perspectives on an Ocean Planet

- Earth Sensor Assembly Module

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esam

The sensors in the earth Sensor Assembly Module (ESAM) give the spacecraft the ability to estimate the orientation of the satellite relative to the earth. This is necessary during certain orientation maneuvers after launch vehicle separation.

The ESAM has two solid-state infrared detectors which automatically scan in a circular pattern to find the earth. The sensors look specifically for the infrared signature of carbon dioxide in the earth's limb. When the sensors find the earth, the ESAM reports the location to the Attitude Control System.