From the "JPL Universe" August 21, 1998
DS2 completes key thermal vacuum testsBy MARK WHALEN
The Deep Space 2 microprobe mission has successfully reached a critical milestone in its development with the completion of thermal vacuum testing.
Deep Space 2 is a New Millennium Program technology validation mission that will piggyback aboard the Mars Polar Lander, which is scheduled to launch Jan. 3, 1999 and land 11 months later. Just minutes before the lander touches down, Deep Space 2 will deploy two small, 2-kilogram (4.5-pound) microprobes beneath the Martian surface to study subsurface materials.
The end-to-end system verification sequences, the last of a series of major environmental tests, were conducted on Lab Aug. 1 to 4. "We had very positive results," said Project Manager Sarah Gavit. "This is a huge milestone in terms of verifying and proving our design end-to-end, because the tests simulated the entire mission in a Mars-like environment."
To simulate Mars' frigid climate, testing was conducted at temperatures as low as minus 110 degrees C (minus 166 F) for the probe's forebody and minus 80 degrees C (minus 112 F) for the aftbody. In addition, pressure testing was performed to prepare the mission for operation in a Martian atmosphere that is less than 1 percent that of Earth, she added.
The 10-centimeter-long (4-inch) forebody contains a drill for collecting a soil sample, a water detection instrument, a soil conductivity experiment and an impact accelerometer, and is designed to burrow up to 0.9 meters (3 feet) into the Martian soil. The circular aftbody, 13 centimeters (5 inches) in diameter, contains the batteries, telecommunications electronics, antenna, atmospheric descent accelerometer and sun sensor, and remains atop the surface. The two modules are connected via a flexible cable that unravels as the forebody dives into the soil after a freefall impact.
"In addition to verifying the probe's performance in a simulated Martian environment, the assembly of the qualification unit also provided invaluable lessons for the assembly of the flight probes," Gavit said. "This is especially important since the requirement for impact survival necessitates that many of the probe's assembly steps be irreversible.
"The skill level of the technicians involved in putting the probe's miniaturized assemblies together is phenomenal," she added. "The JPL Hybrid Laboratory has done an excellent job."
Work is still under way on the design of the microprobe's telecommunications system, which was not part of the qualification tests. The aftbody electronics assembly will be retested with the completed telecommunications system in September. The telecommunications system, together with miniaturized electronics in the forebody, will relay the probe's findings to Mars Global Surveyor for transmission to Earth via the Deep Space Network.
The project will continue with the assembly and test of the flight probes in the next several months. To date, the Mars Polar Lander interface structure, aeroshells, science blocks and most of the aftbody structural assembly are already complete. "Over the coming weeks," Gavit said, "we will be focusing on the integration and test of the forebody prism electronics, including the microcontroller, power electronics and instrument electronics."
Deep Space 2 is scheduled for a mid-October shipment to Kennedy Space Center for its integration onto the Mars Polar Lander cruise ring.
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