NASA's Mars Exploration Rover Opportunity has resumed using its rock
abrasion tool after a pebble fell out that had jammed the tool's
rotors two weeks ago.
The abrasion tool successfully spun a wire brush late Monday to scrub
dust off two patches of a rock inside "Endurance Crater," and
engineering data received Tuesday confirmed that the tool is fully
recovered. Rover wranglers at NASA's Jet Propulsion Laboratory,
Pasadena, Calif., plan to use the tool's grinding rotor next to cut a
hole exposing the interior of the rock.
"We're delighted to be using Opportunity's rock abrasion tool again,"
said Dr. Stephen Gorevan of Honeybee Robotics, New York, lead
scientist for that tool on both rovers. "We had planned to kick out
that pebble by turning the rotors in reverse, but just the jostling of
the rover's movements seems to have shaken it loose even before we
tried that. The rock abrasion tool has functioned beyond engineering
expectations as a window for Mars Exploration Rover science. The new
imaging consultation makes it clear that not only does the tool appear
to be undamaged, but also that its teeth have not worn very much at
all."
Opportunity and its twin, Spirit, have each conducted more than four
months of bonus exploration and discoveries after successfully
completing their three-month primary missions on Mars.
Opportunity's rock abrasion tool has now been used 18 times to grind
into rocks and five times to brush rocks. Spirit's tool has
ground nine times and brushed 28 times. The criteria set in advance
for successful use of the abrasion tools was for each rover to grind
at least one rock.
Mars and Earth are approaching the point in their orbits when Mars, on
Sept. 16, will pass nearly behind the Sun, a geometry called
"conjunction." For several days around conjunction, the
energetic environment close to the Sun will interfere with radio
communications between the two planets. Rover operators have
planned a hiatus in sending up daily commands. The rovers will use
longer-term instructions to continue doing daily research and to
attempt daily communications until the conjunction period is over.
"Based on experience with other spacecraft, we expect that when the
Mars-Sun-Earth angle is 2 degrees or less, the ability to successfully
communicate degrades rapidly," said JPL systems engineer Scott
Doudrick, who has been organizing conjunction operations for both
rovers. "To be cautious, we're allowing three days on either side of
that period."
The planned gap in sending daily plans runs for about 12 days
beginning Sept. 8 for Spirit and Sept. 9 for Opportunity. The rovers
will be instructed ahead of time to continue doing atmospheric
operations and Moessbauer spectrometer readings daily during that
period. No movements of the wheels or the robotic arms are in the
conjunction-period plans, but the camera masts may move for making
observations. The rovers also will continue communicating daily with
NASA's Mars Odyssey orbiter and will also attempt to communicate
directly with Earth.
"The science team gets some time off from the daily planning cycle,
but we will have a full spacecraft team every day, so we will be able
to respond quickly if the rovers communicate a problem to us and
there's a good reason for emergency commands," Doudrick said.
JPL, a division of the California Institute of Technology in Pasadena,
manages the Mars Exploration Rover project for NASA's Science Mission
Directorate, Washington. Additional information about the
project is available from JPL at http://marsrovers.jpl.nasa.gov/
and from Cornell University, Ithaca, N.Y., at http://athena.cornell.edu/
.
