Active Calorimetry Development for Testing of Active Thermal Control Coatings and Devices

Physical Sciences Inc. proposes to develop a calorimeter designed specifically for accurately measuring the solar absorbance (alpha) to infrared emittance (epsilon) ratio, alpha/epsilon, as well as alpha and epsilon, of spacecraft thermal control coatings that can actively change their alpha or epsilon in response to the thermal environment. Our calorimeter is unique; it is autonomous, incorporating its processing and control electronics integrally with the sensor itself. It is lightweight, compact, low-power, and provides real-time measurements and digital output. It requires a small mounting area (~ < 10 cm^2), can be readily distributed over the spacecraft, and can be easily integrated, requiring only a digital communications line and regulated power. In Phase I we designed, fabricated, developed a thermal model for, and calibrated a proof-of-concept calorimeter. We demonstrated its operation by switching the emissivity of a thermal control material incorporated into the calorimeter and verified the resulting change in equilibrium temperature with the calorimeter facing a blackbody in vacuum. Our design showed that the control electronics could be accommodated on a circuit board within calorimeter enclosure. In Phase II we will develop and deliver six fully calibrated, functionally characterized, space environment qualified, easy-to-integrate, flight ready, prototype active calorimeters to AFRL.