[meteorite-list] NASA's Phoenix Mission Faces Survival Challenges

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 28 Oct 2008 16:14:05 -0700 (PDT)
Message-ID: <200810282314.QAA07884_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.cfm?release=2008-199

NASA's Phoenix Mission Faces Survival Challenges
Jet Propulsion Laboratory
October 28, 2008

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.

Media contacts: Rhea Borja/Veronica McGregor 818-354-0850/354-9452
Jet Propulsion Laboratory, Pasadena, Calif.
rhea.r.borja at jpl.nasa.gov
veronica.mcgregor at jpl.nasa.gov

2008-199
Received on Tue 28 Oct 2008 07:14:05 PM PDT