Initial design

In the beginning

Designing electronic subsystems for space vehicles can be considered in two overlapping phases. The circuitry has to carry out the required signal processing functions but also has to be capable of overcoming the particular problems associated with the subsystem existing and operating in the environment associated with the spacecraft.

In the early stages of a design, estimates have to be made of mass, volume and power consumption to determine what is feasible, within the constraints imposed by the spacecraft. Estimates are also required for cost, time and manpower to ensure that the flight hardware can be realistically produced by the required delivery date. Thus it is important to consider as soon as possible what problems associated with the space environment are seriously going to effect these estimates compared to a ground – based design.

A long life mission will have a significant impact on costs due to the requirement for increased reliability of components and manufacturing techniques, and for the introduction of component or system redundancy.

Apart from the requirements of telemetry transmitter power and type of antenna, the orbit can have a very significant effect on cost if it is associated with a high radiation environment. This may require the use of highly specialized, radiation tolerant components which may be difficult to procure. A high radiation environment can also have a major impact on mass where the wall thickness of the structure is no longer defined by structural and electrostatic screening requirements but by its ability to absorb radiation.