MEDIA RELATIONS OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011 http://www.jpl.nasa.gov 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 mission. 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.

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