Risky Business

NASA began the New Millennium Program, which sponsored DS1, to develop and flight validate new technologies, such as the ion engine that would propel the spacecraft, to help lower costs and risks of future space missions. The ion engine is essential for more efficiently propelling spacecraft farther than traditional propulsion systems, yet the engine itself and its interactions with instruments -- particularly plasma sensors such as PEPE -- were unproved. There was a possibility the engine could damage PEPE or render it ineffective because the current coming out of the ion thruster would be far more intense than anything normally found in space.

SwRI engineers cautiously activated PEPE on December 9, 1998, from a distance of more than 4.5 million miles. The instrument immediately began detecting the solar wind and identifying the cloud of photoelectrons hugging the spacecraft. Since that time, PEPE has also identified xenon ions that return to DS1 after collisions inside the ion engine - with no obvious ill effects.

PEPE data have verified that it is safe to use the DS1 ion propulsion system for future space science missions taking plasma measurements. This opens the way for new missions to even more distant solar system bodies.

Published in the Summer 1999 issue of Technology Today®, published by Southwest Research Institute. For more information, contact Maria Martinez.

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