ABSTRACT
This chapter illustrates some specific issues outlined in Chapter 10. I had a firsthand view of some of the effort in developing the system because the customer called me in as a consultant. Ecliptic Enterprises Corporation in Pasadena, CA, developed a video
system for data acquisition. It is a space version of a commercial offthe-shelf (COTS) video system; it is designed for shorter-term missions that approach low-earth orbits. The system uses commercial components to speed development and reduce cost. Inmanyways, the system is simpler and cheaper than most instruments designed for space travel because it does not have some of the requirements that long-lived missions might have. The system captures, processes, transmits, and displays images in real
time for a mission-critical application. The sensors were very similar to those in video cameras. The system compresses and multiplexes the data from the sensors into a single data stream and then sends the data via a telemetry link to a remote location. At the remote location, the support equipment decommutates (demultiplexes), decompresses, displays, and stores the data stream on disk. Figure 11.1 outlines the design of the system. The flight hardware has four
circuit boards: a video-compression board, a multiplexer board, a power supply board, and an analog housekeeping board. A field-programmable gate array (FPGA) on the multiplexer board buffers up the data streams from each sensor. Digital signal processor (DSP) chips on both the compression board and the multiplexer board multiplex data and to compress the images. The analog housekeeping collects temperature data and analog signals from various places on the sensors, converts it to digital format, and then multiplexes the housekeeping data into the data stream for telemetry. Source software code for the DSP chips is written in C. The display
software on the support equipment is a purchased COTS package.
