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Mars Polar Lander Mission Status

December 2, 1999

Twenty-four hours before the Mars Polar Lander is scheduled to arrive at
the south pole of the red planet, flight controllers at NASA’s Jet Propulsion Laboratory,
Pasadena, Calif., report that the spacecraft is making excellent progress as the team
begins around-the-clock monitoring.

Mars Polar Lander is scheduled to land on Mars shortly after noon Pacific
time on Friday, December 3. The first signal is expected to be received at 12:39 p.m. The
entry, descent, and landing sequence is the most complex and challenging part of the

Once the spacecraft is on the ground, a series of activities equally critical to the
success of the mission will begin. If no communication is received from the lander at the
first opportunity at 12:39 p.m., there are many other windows during which the
controllers may hear from the spacecraft during the next few days. Several factors could
potentially delay the first contact without preventing later communication and the
execution of the full mission.

“The team will meet at 2 a.m. Pacific time Friday morning to review flight path
estimates, then at 5:30 a.m. we will make any final course corrections,” said Dr. Sam
Thurman, flight operations manager for the lander at JPL. “Right now it appears the
atmospheric entry angle is just a little steeper than we wanted, but it’s still in the sweet
spot. We have the luxury of examining the terrain and making minor adjustments to reach
the safest part of the target area that the science team has been able to identify.”

During descent, the spacecraft will enter the Martian atmosphere traveling at 6.9
kilometers per second (15,400 miles per hour). Onboard accelerometers will sense when
friction from the atmosphere causes the lander to begin to slow. From that time, it will be
5 minutes and 30 seconds until touchdown on the surface, during which time the
spacecraft will experience G forces up to 12 times Earth’s gravity and the temperature of
the heat shield’s exterior will rise to 1,650 C (3,000 degrees F).

“The powered descent phase is the biggest concern. The Martian atmosphere is
not well known,” said Thurman. “That’s why we have focused most intensely on the
design, testing, and verification of the powered descent and landing system. The key to
minimizing risk is to build a lot of margin and robustness into the vehicle design.”

The Deep Space 2 microprobes, which are piggybacking on the lander, will be
jettisoned to the planet about 5 minutes before the lander enters the Martian atmosphere.
Deep Space 2 Project Manager Sarah Gavit echoed Thurman’s views, saying that a
successful landing depends not only on how and where the probes enter the surface, but
also the entry angle. “We used a variety of techniques, a lot of trial and error, and a
rigorous test program, but the biggest risk is Mars itself,” said Gavit. The goal of Deep
Space 2 is to increase the efficiency and lower the costs of space science missions
through new technologies. “All the new technologies on board make this a lot more risky
than a typical spacecraft,” said Gavit. “To make progress we need to be bold. That’s what
it’s all about.”

Mars Polar Lander is part of a series of missions in a long-term program of Mars
exploration managed by JPL for NASA’s Office of Space Science, Washington, D.C.
JPL’s industrial partner is Lockheed Martin Astronautics, Denver. JPL is a division of the
California Institute of Technology in Pasadena.