Thermal Modeling and Testing of a Nanosatellite's Avionics Board

Abstract

A lumped-capacitance thermal model of an avionics board within the Miniature Autonomous Extravehicular Robotic Camera was developed to predict component temperatures. Subsequently, a thermal vacuum test was conducted to determine the board's measured thermophysical properties and validate temperature predictions. A functional prototype of the board was instrumented with 24 type-T thermocouples and placed in a thermal vacuum chamber. The board was then subjected to two power conditions while the temperature response was recorded. Analysis of the data shows that the measured values of the in-plane thermal conductivity are dominated by the dielectric material. Pretest analysis underpredicted the through-plane thermal conductivity by 63% and the in-plane thermal conductivity was overpredicted by approximately 740%. Additionally, the bulk emissivity of the board was determined using an average temperature of the thermocouples on the back side of the board. The emissivity calculated from measured temperature data, 0.95, was approximately 19% higher than the assumed emissivity used in pretest models, 0.80. Incorporation of the thermophysical properties based on measured data allows the updated model to predict temperatures of the LED board within an uncertainty of ±10°C and to capture the transient response of the board with considerable accuracy.