Opportunity Clears Jammed Rotors, Continues Exploration
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 (CA), 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
"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