Infrared radiometer for the 1969 mariner mission to Mars.

A two-channel radiometer has been developed to measure the equivalent blackbody surface temperatures of the equatorial and colder south polar regions of Mars. Two spectral channels, 8-12 micro and 18-25 micro cover the temperature range of 140 K to 325 K. Evaporated thin film thermopile detectors of unusual design provide temperature resolution capability of better than 0.50 degrees C for a surface temperature of 140 K. A simple low power stepping mirror in conjunction with a dc restore-memory circuit eliminates the need for a chopper, but at the same time provides a zero radiation reference and an inflight calibration point. The complete radiometer weighs 3.75 kg and consumes 3 W of power.