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DS2 completes key thermal vacuum tests
By 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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