A 120 X 5 degree instantaneous field-of-view Wide Angle Earth Sensor has been developed for use on missions that are prohibited from viewing the Earth with the payload sensor. Developed especially for NASA's WIRE (Wide-Field Infrared Explorer) mission, the WAES consists of two Sensor Heads and an Electronics Control Unit. On the WIRE mission the sensor heads are arranged back to back 180 degrees apart such that they can monitor one axis of rotation, while a sun sensor is used for the other axis. This is of extreme importance to these missions, as the telescope features a detector that is cooled by a solid hydrogen cryogen. Accidental viewing of the Earth or sun would cause the cryogen to boil off and end the mission prematurely. The predicted accuracy of 1.5 degrees exclusive of radiance errors and 3.5 degrees inclusive of radiance errors.
The thermistor infrared detector or bolometer is the detector of choice in many classical remote sensing applications such as horizon sensing, noncontact thermometry, and industrial applications. In recent years, the authors have developed a thin film process where the thermistor material is deposited from a target directly onto the substrate. This is an advance over the labor intensive ceramic technology, where sintered flakes of the thermistor are bonded to the substrate. The thin film technique permits a variety of device constructions and configurations. Detectors fabricated on heat-sunk ceramic substrates can withstand high operating temperatures and large incident optical power, in both pulsed and CW laser measurements. For dc or low frequency measurements, the films can be deposited onto a thermally isolated membrane with applications in motion sensing, gas detection, and temperature measurement. Utilizing advances in micromachining a 2D array of thermally isolated microbolometer sensors, integrated onto a silicon wafer containing readout circuitry may be achieved. This paper describes the construction of the sputtered film thermistor detectors, their operation, and applications.