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Kathy Barnstorff
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RELEASE : 08-032
08-032: Langley Researchers Work to Help Phoenix Land on Mars

HAMPTON, Va. - NASA scientists and engineers expect to have an out of this world Memorial Day weekend, even though they'll be hard at work. Their mission is to land a spacecraft safely on Mars Sunday evening.

Three researchers from NASA's Langley Research Center in Hampton, Va. are part of the team working to guide the Mars Phoenix Lander to a soft landing on the northern polar regions of Mars, a never-before explored area of the Red Planet. Their primary responsibility is to help during entry, descent and landing (EDL) or "seven minutes of terror" as it's sometimes called.

"Seven minutes of terror means that the spacecraft has seven minutes from entry into the Martian atmosphere until touchdown," said Langley aerospace engineer Jill Prince. "You can't fix any possible problems in those seven minutes when they're actually happening, because it takes 15 minutes for the signal from Phoenix to reach earth."

Prince will be in the mission control room at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif., Sunday, May 25. She'll be at the console running computer simulations of entry, descent and landing scenarios and hoping to celebrate a successful landing as early as 7:53 p.m. EDT. Two other Langley engineers will be nearby with other EDL team members.

Phoenix launched on August 4 last year for the 422 million mile journey to Mars. It's preparing to begin a three-month mission to taste and sniff fistfuls of Martian soil and buried ice. The solar-powered three-legged robotic lander will manipulate a 7.7-foot arm to scoop up samples of underground ice and soil lying above the ice. Onboard laboratory instruments will analyze the samples. Cameras and a Canadian-supplied weather station will supply other information about the site's environment.

One research goal is to assess whether conditions at the site ever have been favorable for microbial life. The composition and texture of soil above the ice could give clues to whether the ice ever melts in response to long-term climate cycles. Another important question is whether the scooped-up samples contain carbon-based chemicals that are potential building blocks and food for life.

But first Phoenix must make it through the challenging Mars atmosphere. "When we hit the atmosphere we're doing almost 13,000 miles an hour," said Eric Queen, Langley research engineer. "The friction of the atmosphere slows us down until we get to about 900 miles an hour. At that point we open a parachute and that slows us down further. Eventually we drop off the parachute and we have rockets that fire on the vehicle to come to a soft landing."

Computer simulations at Langley showed there could be an issue with the parachute falling on top of the lander in low wind, so Queen said researchers suggested adding a "backshell avoidance maneuver. When Phoenix drops away from the parachute it actually moves to the side so that it can land safely and the parachute can go its own way."

Langley's expertise in Mars landers started decades ago when it led the Viking project in the 1970s. Viking successfully landed two spacecraft on Mars in 1976. Researchers are still using data from those missions today.

"Many aspects of the design are still relying on the technology, the heritage of the Viking vehicle itself. The capsule shape is very similar," said Prasun Desai, Langley Mars Phoenix Lander lead. "Viking also did a soft landing on Mars back in the mid-70s and we're doing the same here. So we're relying on a lot of the heritage that Viking pioneered."

Phoenix uses hardware from a spacecraft built for a 2001 launch that was canceled in response to the loss of a similar Mars spacecraft during a 1999 landing attempt. Researchers who proposed the Phoenix mission saw the unused spacecraft as a resource for pursuing a new science opportunity.

The Phoenix mission is led by the University of Arizona, Tucson, with project management at JPL. The development partnership is with Lockheed Martin, Denver. International contributions are from the Canadian Space Agency; the University of Neuchatel, Switzerland; the universities of Copenhagen and Aarhus, Denmark; the Max Planck Institute, Germany; and the Finnish Meteorological Institute.

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