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University of Arizona


Peter H. Smith, for the SSI/RAC, 520-621-2725
William V. Boynton, for TEGA, 520-621-6941
Ralph Lorenz, for Mars Microprobe Project, 520-621-5585 

December 21, 1998

UA teams head to Cape Canaveral for Jan. 3 Mars Polar Lander launch

By Lori Stiles

A twin of the famous Pathfinder lander stereo camera, a close-up camera mounted on a six-foot-plus robotic arm and the tiniest out-of-this world ovens that ever cooked alien soil will be launched to Mars on Sunday, Jan. 3.

Researchers at The University of Arizona in Tucson poured considerable brainpower and time into these three instruments, which are a major part of the integrated payload called "MVACS," or the Mars Volatiles and Climate Surveyor. It is on the Mars Polar Lander, a mission to search for water after landing at planet's south pole in December 1999.

Dozens of scientists, engineers, students and colleagues from the UA Lunar and Planetary Laboratory will celebrate New Year's weekend at Cape Canaveral, Fla., anticipating the Sunday afternoon launch on which they have so much riding.

"We're going to a whole new place on Mars, and I can promise you won't be disappointed," said Peter H. Smith of the UA Lunar and Planetary Laboratory (LPL).

Smith heads the UA group who for this mission produced the Surface Stereo Imager, or SSI. It is identical to the Pathfinder camera that landed on Mars on July 4, 1997. That camera returned hundreds of images that excited not just scientists, but children and others with healthy imaginations who followed the Pathfinder news.

The overall goal for the 90-day MVACS mission is to study the distribution and behavior of water on Mars and the history of the Martian climate. David A. Paige of the University of California-Los Angeles is principal investigator for MVACS, which also includes a meteorology package. The big questions include: Where is all the water that once flooded Mars? What happened to the water through time? Did Mars once have a warmer and wetter climate that could have supported life? What causes Mars' climate change?

Also for this mission, together with scientists from the Max Planck Institute for Aeronomy, Smith and his team created RAC, or the Robotic Arm Camera. RAC is mounted near the cup-size scoop at the end of a robotic arm. While the SSI on the lander shows scientists the big picture of where around the lander they might most productively dig, the RAC shows them up close what they're looking at. The RAC is able to resolve an image of a single human hair from a distance of a half an inch, Smith said, so on Mars, researchers will learn a lot from a good-sized chunk of gravel or even from finer grains of sand.

The RAC will inspect trench walls as the robotic arm digs. It will look for ice, bright and dark layers in Mars soil, and any other clues to the history of the planet, Smith said.

Lamps mounted on RAC shine in red, blue and green from several directions. LPL engineer Roger Tanner is largely responsible for the design of the lights, which took considerable time to perfect. Without the colored lights, the scientists would see only black-and-white images. With them, they will see color as well as structure of the soil.

The TEGA, or Thermal and Evolved Gas Analyzer, represents years of "blood, sweat and tears," said William V. Boynton, UA professor of planetary sciences and head of the group that designed, built and tested this experiment.

TEGA will use electric current to heat soil samples collected by the robotic arm scoop. RAC then will photograph these soil samples. The scoop will dump the dirt onto a screen that then filters samples into TEGA.

TEGA has eight analyzers, each holding two ceramic ovens, each about the size of a piece of macaroni. In each analyzer, one oven will remain empty, the other will be fed four one-thousandths of an ounce of Mars soil. The ovens heat at a controlled rate of a few degrees per minute up to 1,000 degrees Celsius. The ovens leak heat; they are not perfectly insulated. By measuring heat loss in the empty oven and subtracting that amount from the heat in the filled oven, researchers know precisely how much energy the soil samples absorb. Also, a carrier gas wafts all gases released during heating into a 'gas analyzer' chamber. Scientists will learn how much frozen water and carbon dioxide are in the soil, as well as what gases are locked in various minerals.

Boynton said he began thinking of something like TEGA years ago, an idea sparked by a seminar he attended as a graduate student. He planned to include such an instrument on the the Comet Penetrator Lander, for which he was principal investigator, part of the Comet Rendezvous/Asteroid Flyby Mission. The flyby mission evolved into NEAR, the Near Earth Asteroid Rendezvous mission, which arrives Jan. 10 at the asteroid 433 Eros. Boynton is currently on the science team for the NEAR Gamma-Ray/X-Ray Spectrometer experiment. He also is team leader for the Mars Surveyor Program 2001 Gamma Ray Spectrometer Experiment.

Mike Williams, senior LPL engineer, said that TEGA is rare in UA history because the space project was designed from scratch, assembled and tested entirely at the University, without a space industry firm as major contractor.

The daunting task -- all within a 3-year deadline -- was to design, build and test a flight-ready science instrument with near-microscopic, delicate parts able to survive the force of 70 Gs at launch (force 70 times that of Earth's gravity) and, after the journey to Mars, heat soil at around minus 80 degrees Celsius to 1,000 degrees Celsius.

Unexpected challenges included the news that the MVACS package, then integrated with the lander at Martin-Marietta laboratories in Denver, would be tested at very cold temperatures. Extreme cold triggers TEGA into action -- and it delivers a once-only performance, Williams said. He and his colleagues had to quickly devise a way to lock all TEGA's triggering mechanisms for the cold test, then unlock it all again for launch.

"It took a big team effort, which is the only way this would have worked," Williams said. Those at the LPL who worked on TEGA gave "three-and-a-half years" of their lives to the 3-year project, he added. "It has been the most difficult project I've worked on here. I'll be glad to see it gone so I won't have to do anything more on it," he said. "Still, it is wonderful to know that something we created will actually be there, on Mars. This is something that happens only once in a lifetime."

Ralph D. Lorenz, a research associate at the LPL who worked on the TEGA, also is a scientist for the Deep Space 2 Mars Microprobe Project, a $2.8 million experiment piggybacking on the Mars Polar Lander.

The microprobes are two basketball-size aeroshells that ride underneath the lander's solar panels during its 11-month cruise to Mars. They will crash onto the Martian surface at a velocity of about 200 meters per second, about 60 miles (100 km) from the landing site. Each aeroshell will shatter on impact, releasing a miniature two-piece science probe that will punch into the soil to a depth of up to 2 meters (6.6 feet).

The microprobes are primarily to test key technologies for future missions that will land multiple microprobes on the surfaces of other worlds, but they also share the major science mission goal, which is to determine if water is present in the Martian subsurface. The tiny science stations will also measure temperature and monitor local Martian weather for 50 hours in the frigid Mars environment.

Whether batteries on the microprobes will survive impact is uncertain, Lorenz noted. So far, no penetrator has successfully reached another planet or moon. The penetrators will strike the surface with a force equivalent to 80,000 times their weight here on Earth, he added.

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