The Integrated Housekeeping Unit: A Method of Telemetry, Command and Control for Small Spacecraft

In a small satellite environment where the total power budget for telemetry command, ranging and all satellite control functions is not to exceed 2 Watts rather focused measures must be taken to consolidate these functions. Since 1975 AMSAT has been developing the concept of the Integrated Housekeeping Unit (IHU) for this purpose. The IHU combines the traditional telemetry encoder and command decoder with a multi-tasking microcomputer so that this single module is capable of handling all spacecraft functions simultaneously. The nature of the orbit planned for the series of spacecraft for which this unit was developed results in a high radiation environment tor the IHU. Special attention was paid to this in the design. A high-level language has been developed for the IHU. Called IPS, it operates on up to eight simultaneous tasks, including telemetry and command processing, and navigational functions concerned with orbital insertion and station keeping. The development of this concept is described in this paper.