NASA's Phoenix Mars
Lander To Begin Rasping Frozen Layer
(15 July 2008) A powered rasp on the
back of the robotic arm scoop of NASA's Phoenix Mars Lander is being tested for
the first time on Mars in gathering sample shavings of ice.
The
lander has used its arm in recent days to clear away loose soil from a
subsurface layer of hard-frozen material and create a large enough area to use
the motorised rasp in a trench informally named "Snow White."
The
Phoenix team prepared commands early Tuesday for beginning a series of tests
with the rasp later in the day. Engineers and scientists designed the tests to
lead up to, in coming days, delivering a sample of icy soil into one of the
lander's laboratory ovens.
"While Phoenix was in development, we added
the rasp to the robotic arm design specifically to grind into very hard surface
ice," said Barry Goldstein, Phoenix project manager at NASA's Jet Propulsion
Laboratory, Pasadena, Calif. "This is the exactly the situation we find we are
facing on Mars, so we believe we have the right tool for the job. Honeybee
Robotics in New York City did a heroic job of designing and delivering the rasp
on a very short schedule."
The rasp bit extends at a shallow angle out
of an opening on the back of the scoop at the end of the 2.35-meter-long
(7.7-foot-long) robotic arm. To use it, the back surface of the scoop is placed
on the ground, and a motor rotates the rasp. The angle of the rasp is increased
from nearly horizontal to slightly steeper while it is rotating, so the tool
kicks shavings sideways onto a collection surface just inside the opening.
After the rasp stops, a series of moves by the scoop then shifts the collected
shavings from the back of the scoop, past baffles, to the front of the scoop.
The baffles serve to keep material from falling out of the rasp opening when
the scoop is used as a front loader.
The commands prepared for Phoenix's
activities Tuesday called for rasping into the hard material at the bottom of
the Snow White trench at two points about one centimetre (0.4 inch) apart. The
lander's Surface Stereo Imager and robotic arm camera will be used to check the
process at several steps and to monitor any resulting sample in the scoop for
several hours after it is collected.
Collecting an icy sample for an
oven of Phoenix's Thermal and Evolved-Gas Analyzer (TEGA) may involve gathering
shavings collected at the rasp opening and scooping up additional shavings
produced by the rasp. The Phoenix team has been testing this combination on
simulated Martian ice with a near-replica model of Phoenix in a test facility
at the University of Arizona, Tucson.
The Phoenix mission is led by
Peter Smith of the University of Arizona with project management at JPL and
development partnership at Lockheed Martin, Denver. International contributions
come from the Canadian Space Agency; the University of Neuchatel; the
universities of Copenhagen and Aarhus, Denmark; Max Planck Institute, Germany;
and the Finnish Meteorological Institute.
(source: NASA Jet Propulsion
Laboratory)
