Pre-berth temperatures of exterior spacecraft components are a critical issue1. They’re strongly driven by several factors 2:
(1) The capacity of the elements to store heat (their “thermal masses” or “thermal capacity”)
(2) How the components absorb light and emit heat (their “thermal optical properties”)
(3) How thermal energy gets transferred from one part of the spacecraft to another (“thermal conductance“)
(4) Where the spacecraft is located in space (“orbital elements”), particularly altitude and inclination
(5) Where the components are pointing (their “orientation” or “attitude”)
Factors (4) and (5) define the spacecraft’s time-varying pattern of exposure to:
(a) Deep space
(b) Direct sunlight
(c) Sunlight reflected from Earth’s clouds and oceans
(c) Other surfaces of the immediate spacecraft
On orbit, the exposures alternate to cause temperature variations in the exposed components that look like a sine wave. The resulting oscillations of temperature happen either faster or slower depending on the thermal masses of the two elements, and by the thermal conductance path between the CBM and those masses. See (for example) Chapters 2, 4 and 5 of Gilmore3 for background on these issues, which are fundamental to the development of most spacecraft.
Footnotes- MIL-A-83577B “Assemblies, Moving Mechanical, For Space and Launch Vehicles, General Specification for” (1978)[↩]
- Conley, Peter L. (ed), “Space Vehicle Mechanisms: Elements of Successful Design”, John. Wiley & Sons (1998), Chapter 20 “Thermal Design”[↩]
- Gilmore, David G (ed.), “Satellite Thermal Control Handbook”, The Aerospace Corporation Press, El Segundo, CA (1994).[↩]