Deep Space 1 -- Futuristic Space Probe Powered By A Solar-Electric Propulsion System

The spacecraft, Deep Space 1, will attempt close flybys of an asteroid and possibly two comets, said CU-Boulder Associate Professor Fran Bagenal of the astrophysical and planetary sciences department. One of 15 science team members selected for the mission by NASA, Bagenal, with the help of Frank Crary, of CU's Laboratory for Atmospheric and Space Physics, will analyze data collected on charged particles and magnetic fields surrounding the asteroid and comets.

Deep Space 1 is scheduled for launch Oct. 25 aboard a three-stage Delta rocket from Cape Canaveral, Fla. Weighing only 1,000 pounds, the craft is packed with miniature instruments and devices designed to test 12 innovative technologies.

"The most exciting part of this mission to me is the ion-drive propulsion system," Bagenal said. "This is the first time it will be used for deep-space travel to propel a spacecraft out of the sun's gravity."

The propulsion system relies on the generation and bombardment of a chamber of xenon gas with hot, negatively charged electrons. The chamber is heated by solar energy that has been converted to electricity. As the electrons strike the xenon atoms, they knock off atom electrons, resulting in positively charged atoms, or ions.

The ions then are accelerated by an electric field to high speeds and expelled out the rear of the engine at about five miles per second, creating 3,000 tiny beams of thrust. Although the thrust is small -- increasing the speed of the craft by about 30 feet per second each day -- it eventually will propel the spacecraft to a speed of 8,000 miles per hour. The spacecraft will turn itself off periodically, allowing it to coast through space for weeks at a time.

"The ion-drive system would make being on Deep Space 1 like being in a car, rather than on the top of a rocket," she said. "It can drive around the solar system, changing its trajectory as it navigates using its computers and images of the stars taken by the on-board camera."

Because of the weight problem in lofting missions to the outer solar system, "we squeezed all the instrumentation way down," she said. "But if it works, we will move into a new era of space flight, going to a lot of new places more swiftly and easily."

Two primary instruments on board the craft are a camera and a particle detector, said Bagenal. The camera, which can take images in the visible, ultraviolet and infrared spectrums, weighs about 28 pounds -- or about six times less than the camera currently on the way to Saturn aboard NASA's Cassini mission. Deep Space 1 is managed by NASA's Jet Propulsion Laboratory in Pasadena, Calif.

The particle detector, weighing less than seven pounds, is about four times lighter than the particle detector aboard Cassini, she said. "Both of these instruments are small, light and have high performance capabilities."

Bagenal, who also has worked as a mission scientist on NASA's Voyager and Galileo missions with charged particles and magnetic fields, is particularly interested in the effect of the solar wind. The solar wind is believed to knock atoms off asteroids and comets in a process known as "sputtering," possibly ionizing them in the process.

The Deep Space 1 encounter with Asteroid 1992KD is expected to occur in July 1999, perhaps passing as close as three miles, she said. If all goes well, the craft is then expected to fly close by a burned out comet and an active comet. With the orbits of 250 asteroids and 250,000 stars stored in its computer memory, the craft can execute trajectory changes without the need for commands from Earth.

"This is a check-out mission to test new technology," said Bagenal. "There is no point in sending such radical technology into the outer solar system until we try it out and see if it succeeds in the inner solar system."

Bagenal said she is fairly optimistic the spacecraft will work. "We need to learn from these cheaper, faster test missions so we can move on to doing important science in other areas of space."