Tim Gallagher
Mars Pathfinder, Camera Control Electronics Designer
Lockheed Martin, Colorado

My Involvement With Mars

About three to four years ago while working on an instrument package going to Saturn's moon Titan, I was asked to join the Mars Pathfinder team because of my previous experience with imaging electronics. This was to be a fast-paced design proving NASA's quicker, simpler and cheaper philosophy for the next generation of small spacecraft systems.

The Imager For Mars Pathfinder (IMP) design, as quoted from the Mars Pathfinder forum "is a stereo imaging system with color capability provided by a set of selectable filters for each of the two camera channels." Please refer to the Web page above for a more detailed description of the science packages. Note that there are two main parts of the Pathfinder: the instruments or payload such as the IMP and rover Sojourner, and the spacecraft that delivers the payload to Mars. The design, launch and control of a spacecraft is very different from the development of an instrument package. The IMP system is basically along for the ride and hopefully after a successful journey and landing on Mars, it will start sending back pictures.

Our design interfaces included a Charge Coupled Device (CCD) and an IBM computer system used to control the taking of pictures (images). A CCD converts light (photons) to an electrical signal, which after processing, forms a picture. Basically, we built the electronic modules in-between.

After studying the CCD and IBM interfaces we started the design in earnest. To save space and cost it was decided to use Very Large Scale Integration (VLSI) circuits such as a Memory Multi-Chip Module (MCM) and a field-programmable Gate Array (FPGA). The Memory MCM could hold multiple pictures allowing the IBM computer to read out the images at its leisure while performing other critical tasks. The Gate Array was engineered to contain many smaller control circuits inside which saved space, weight and costs.

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