NASA's Phoenix Mission Faces Survival Challenges

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
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Rhea Borja/Veronica McGregor 818-354-0850/354-9452
Jet Propulsion Laboratory, Pasadena, Calif.
Rhea.R.Borja@jpl.nasa.gov
Veronica.mcgregor@jpl.nasa.gov

NEWS RELEASE: 2008-199 October 28, 2008

NASA's Phoenix Mission Faces Survival Challenges

PASADENA, Calif. -- In a race against time and the elements, engineers with NASA's
Phoenix Mars Lander mission hope to extend the lander's survival by gradually shutting
down some of its instruments and heaters, starting today.

Originally scheduled to last 90 days, Phoenix has completed a fifth month of exploration in
the Martian arctic. As expected, with the Martian northern hemisphere shifting from
summer to fall, the lander is generating less power due to shorter days and fewer hours of
sunlight reaching its solar panels. At the same time, the spacecraft requires more power to
run several survival heaters that allow it to operate even as temperatures decline.

"If we did nothing, it wouldn't be long before the power needed to operate the spacecraft
would exceed the amount of power it generates on a daily basis," said Phoenix Project
Manager Barry Goldstein of NASA's Jet Propulsion Laboratory, Pasadena, Calif. "By
turning off some heaters and instruments, we can extend the life of the lander by several
weeks and still conduct some science."

Over the next several weeks, four survival heaters will be shut down, one at a time, in an
effort to conserve power. The heaters serve the purpose of keeping the electronics within
tested survivable limits. As each heater is disabled, some of the instruments are also
expected to cease operations. The energy saved is intended to power the lander's main
camera and meteorological instruments until the very end of the mission.

Later today, engineers will send commands to disable the first heater. That heater warms
Phoenix's robotic arm, robotic-arm camera, and thermal and evolved-gas analyzer (TEGA),
an instrument that bakes and sniffs Martian soil to assess volatile ingredients. Shutting
down this heater is expected to save 250 watt-hours of power per Martian day.

The Phoenix team has parked the robotic arm on a representative patch of Martian soil. No
additional soil samples will be gathered. The thermal and electrical-conductivity probe
(TECP), located on the wrist of the arm, has been inserted into the soil and will continue to
measure soil temperature and conductivity, along with atmospheric humidity near the
surface. The probe does not need a heater to operate and should continue to send back data
for weeks.

Throughout the mission, the lander's robotic arm successfully dug and scraped Martian soil
and delivered it to the onboard laboratories. "We turn off this workhorse with the
knowledge that it has far exceeded expectations and conducted every operation asked of
it," said Ray Arvidson, the robotic arm's co-investigator, and a professor at Washington
University, St. Louis.

When power levels necessitate further action, Phoenix engineers will disable a second
heater, which serves the lander's pyrotechnic initiation unit. The unit hasn't been used since
landing, and disabling its heater is expected to add four to five days to the mission's
lifetime. Following that step, engineers would disable a third heater, which warms
Phoenix's main camera -- the Surface Stereo Imager --and the meteorological suite of
instruments. Electronics that operate the meteorological instruments should generate
enough heat on their own to keep most of those instruments and the camera functioning.

In the final step, Phoenix engineers may turn off a fourth heater -- one of two survival
heaters that warm the spacecraft and its batteries. This would leave one remaining survival
heater to run out on its own.

"At that point, Phoenix will be at the mercy of Mars," said Chris Lewicki of JPL, lead
mission manger.

Engineers are also preparing for solar conjunction, when the sun is directly between Earth
and Mars. Between Nov. 28 and Dec. 13, Mars and the sun will be within two degrees of
each other as seen from Earth, blocking radio transmission between the spacecraft and
Earth. During that time, no commands will be sent to Phoenix, but daily downlinks from
Phoenix will continue through NASA's Odyssey and Mars Reconnaissance orbiters. At
this time, controllers can't predict whether the fourth heater would be disabled before or
after conjunction.

The Phoenix mission is led by Peter Smith of the University of Arizona, Tucson, with
project management at the Jet Propulsion Laboratory and development partnership at
Lockheed Martin, Denver. International contributions come from the Canadian Space
Agency; the University of Neuchatel, Switzerland; the universities of Copenhagen and
Aarhus in Denmark; the Max Planck Institute in Germany; and the Finnish Meteorological
Institute. The California Institute of Technology in Pasadena manages JPL for NASA.

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