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By Greg Clark
Arizona Daily Wildcat
October 10, 1997

UA scientists design new generation of spacecraft


Graphic Courtesy of NASA
Arizona Daily Wildcat

  1. Miniature Camera/Spectrometer
  2. Experiment with "intelligent" power switch
  3. Microelectronics experiment to consume less power
  4. Diagnostics for the Ion Thruster
  5. Ion Thruster
  6. Solar Concentrator Arrays
  7. Experimental "cable free" incorporation of microelectronics into spacecraft

This diagram shows the Deep Space 1 spacecraft that will explore Comet West-Kohoutek-Ikemura after flying by Mars and an asteroid by late summer of 2000.

About five years ago, UA scientist Dave Brown and three colleagues had an idea.

The four wanted to come up with new and better instruments to find out just how the solar system works.

In July, NASA will launch a new generation of spacecraft, a generation Brown and other University of Arizona Lunar and Planetary Laboratory scientists have labored to bring forth.

NASA has named three UA scientists, Robert H. Brown, Dan Britt and Bill Sandel, as members of a team that will analyze data from the Deep Space 1, a revolutionary new spacecraft.

They will serve on the mission's science team to analyze data from the craft's flight past a small asteroid, Mars and a comet.

The spacecraft will be powered by an ion beam, and be able to make many of its own navigational decisions, said Brown, who was involved in designing instruments that became the prototype for one of those on Deep Space 1.

The spacecraft and its instruments are steps in a new direction for NASA, which is experimenting with several new technologies to make space exploration cheaper and easier, Brown said.

Deep Space 1 will carry two scientific instruments. One, called MICAS, for miniature integrated camera spectrometer, was designed and assembled in large part at the UA. It will allow scientists to determine the physical and chemical characteristics of its targets. The second instrument will measure charged particles and electronic fields.

MICAS functions as three separate instruments, a camera and two spectrometers, and is built entirely out of silica carbide, a strong and lightweight ceramic developed under the Department of Defense's Star Wars program, Brown said.

The instrument weighs 7 kilograms, uses 5 watts of electricity and cost about $8 million.

The instruments that perform a similar set of functions on the Cassini spacecraft, which Brown has worked on, weighs 100 kilograms, uses 100 watts of electricity and cost about $100 million, he said.

Cassini is scheduled for launch on Monday to study Saturn and its moons.

"This is a brand new approach to instrumentation, and if it works, which we expect it will, it will set a new standard for space exploration," Brown said.

One of the most powerful advances in technology used by Deep Space 1 is its solar electric propulsion system, "the 'ion drive' of science fiction," Brown said.

Instead of using chemical fuel and burning it to produce thrust, the craft will use solar electricity and about 80 kilograms of the inert gas xenon to produce an ion beam.

The propulsion system takes xenon and knocks off an electron to produce a charged particle, which is accelerated through an electric field, Brown said.

The process works the same way a television shoots a beam of electrons through a picture tube, he said.

Solar panels on Deep Space 1 produce the electricity needed to ionize xenon and to produce the magnetic fields.

The ion beam thruster is powerful and efficient, Britt added.

"Pound-for-pound it will deliver 10 times the thrust of any chemically-fueled rocket possible," he said.

The subjects of Deep Space 1's studies are also new for NASA.

"We've flown by only two asteroids in all of human history, and for a comet, this will be a first for NASA, Britt said.

The European Space Agency launched a probe that passed by Comet Halley in 1986, but the images were fuzzy, Brown said.

When Deep Space 1 passes Comet P/West-Kohoutek-Ikemura in the year 2000, outside of Mars' orbit, the comet will be much less active than Halley was, giving scientists a better opportunity to see the nucleus.

Comets are important to scientists because they represent an early age in the evolution of the solar system.

"The early solar system had lots of (comets)," Britt said. "Most went into the formation of the gas giants, Jupiter, Saturn and Neptune, but the ones that are left are records of the processes that were active 4.5 billion years ago in the making of planets."

Comets are also interesting because they are chemically very active, Sandel said.

Sandel, who specializes in ultraviolet spectroscopy, has spent the past two years working on MICAS. He hopes Deep Space 1 will reveal the chemical processes that occur on comets.

"Comets seem to have a uniform composition, but gases come off the nucleus in jets," Sandel said. "This is the first time we will be able to see how the jets behave."

Sandel also hopes to be able to detect the kinds and numbers of gasses present the comet's nucleus.


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