TABLE OF CONTENTS Spacecraft thermal control is a process of energy management in which environmental heating plays a major role. The principal forms of environmental heating on orbit are direct sunlight, sunlight reflected off Earth (albedo), and infrared (IR) energy emitted from Earth. During launch or in exceptionally low orbits, there is also a free molecular heating effect caused by friction in the rarefied upper atmosphere. This chapter gives an overview of these types of environmental heating.
The overall thermal control of a satellite on orbit is usually achieved by balancing the energy emitted by the spacecraft as IR radiation against the energy dissipated by its internal electrical components plus the energy absorbed from the environment; atmospheric convection is absent in space. Figure 2.1 illustrates this relationship.
Like a spacecraft's temperature, Earth's temperature is the result of a balance between absorbed and emitted energy. If one considers Earth and its atmosphere as a whole and computes averages of absorbed and outgoing energy over long time periods, one finds that the absorbed solar energy and the IR radiant energy emitted by Earth are essentially in...
