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 long wavelength infrared emittance (epsilon) ratio, alpha/epsilon, of spacecraft thermal control coatings that can actively and controllably change their alpha or epsilon in response to the thermal environment. Additionally, we propose approaches to determine absolute values of alpha and epsilon on orbit. The unique feature of our calorimeter is that it is autonomous, incorporating its own processing and control electronics, which is highly miniaturized and integral with the sensor itself. The unit is lightweight (~ 150 g), compact (~ < 5 cm diameter x ~ < 5 cm long), low power (~ < 100 mW without heater, ~ < 500 mW with heater), and provides real-time measurements and digital output to the spacecraft data system. It requires a small mounting area (~ < 5 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 will design, fabricate, and calibrate a proof-of-concept calorimeter, and also develop proof-of-concept breadboard electronics and determine the required miniaturization level. In Phase II we will develop prototype calorimeters with integral miniaturized electronics.