[meteorite-list] Spirit Take A Bite Out Of Rock In The Name of Science

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:31:20 2004
Message-ID: <200402090533.VAA21178_at_zagami.jpl.nasa.gov>

http://www.spaceflightnow.com/mars/mera/040207spiritrat.html

Rover takes a bite out of rock in the name of science
BY JUSTIN RAY
SPACEFLIGHT NOW
February 7, 2004

Its two diamond-tipped teeth gnawing at 3,000 revolutions per minute, the
Mars rover Spirit has bore a hole in Adirondack, providing scientists a window
inside the volcanic rock.

"It is a great day for robotics and planetary exploration," Stephen Gorevan of
Honeybee Robotics, lead scientist for the drilling device, told reporters during a
teleconference Saturday.

The Rock Abrasion Tool, or RAT, located on the end of Spirit's moveable arm
performed the three-hour job Friday night (U.S. time). The arm then pointed its
science instruments into the hole to make detailed observations that will be
compared with data collected about the rock's exterior.

The grinding occurred on the patch of Adirondack that was brushed free of dust
a day earlier using bristles on the RAT.

After the RAT was placed on the rock Friday, engineers awaited word from
Spirit. But a communications session with the rover flooded Mission Control
with error messages. A software bug had cropped up.

"It is associated with how we set the particular currents for the motors that
drive the RAT. It just happens under certain circumstances the software
decides to complain on a fairly rapid basis. The problem is that crowds out the
other telemetry and data we are looking for in the downlink," mission manager
Matt Wallace said.

"We were worried, but it turns out everything was fine," Gorevan said.

In a later data relay session, Spirit uplinked the news of a successful RAT'ing
to the orbiting Mars Odyssey spacecraft for transmission to anxious controllers
on Earth.

"We learned that we had indeed succeeded," Gorevan said. "This is an
encounter with an unstructured environment all of these millions of miles away
from the Earth and it was an incredible achievement. We had no idea what the
strength of the rock was yet we put a nice, full circle hole in a rock on Mars for
the first time."

The hole carved is 2.7 millimeters (0.1 inch) deep and 45.5 millimeters (1.8
inches) diameter.

"A lot of people asked me 'did we expected to go deeper?' All I can say is I won
the pool," Gorevan joked. "It was just about right where I expected. It was very
clearly a strong rock; it gave us a lot of resistance. That's why we needed at
least three hours to go this deep."

The drilled area on Adirondack was slightly angled and had a few depressions.
As a result, the RAT didn't affect a few areas within the grinding circle.

"When you see the image, it almost looks like a Pac Man. By that I mean it
looks like it has a mouth and eye," Gorevan said, noting that those parts sit
below the 2.7 millimeters.

The grinding process had several steps as Gorevan explained.

"First, the RAT is placed on the rock and if it is properly placed, switches get
triggered indicating proper placement. We had to wait for a signal on the ground
to show that was OK. Then we sent up essentially a 'go' to execute the rest of
the sequence.

"What happens next is what we call a seek-scan. The RAT actually seeks the
highest peaks in the target area, finds them and grinds them down one by one
until it has achieved a full circular cut.

"And then the last 10 minutes is reserved for a cleaning operation because we
produce an awful lot of cuttings. You will see them in the image on the rim. This
is a 10-minute brushing by two brushes of the excavation so that we have a
nice, clean surface for the MI, APXS and Mossbauer.

"I would bet, I can't prove it, but from our ground tests it's so clean that if you
licked your finger, wiped it, you wouldn't see anything on your finger from the
bottom of that excavation."

The RAT tools are unlike any device operated on Mars before. Both Spirit and
Opportunity have RATs to strip away the weathered surfaces of rocks. The
rovers are exploring the Red Planet to find evidence of past water on Mars.

"The Rock Abrasion Tool is a very sophisticated tool...It has three motors on it.
We are able to grind very slowly and detect peaks in a micro sense, shave them
down until we achieved a full circle," Gorevan said.

"Two little diamond heads moving at 3,000 rpm just sweep along that surface,
cutting layer upon layer. If you gave us three hours, we'll cut in small layers,
we'll make progress after a while. That's why we only got 2.7 millimeters. On a
strong rock, we want to cut thin layers. That's the way we set the parameters."

After finishing the RAT'ing, the Mossbauer Spectrometer was placed into the
hole to look for iron-bearing minerals. The rover was slated to switch
instruments overnight so the Alpha Particle X-Ray Spectrometer could collect
elemental composition measurements.

During the next workday at Gusev Crater, which begins Saturday afternoon
(U.S. time), Spirit was scheduled to take microscopic images. Then the arm
would be stowed so Spirit could drive in reverse from the pyramid-shaped rock,
leaving a spot the rover has been sitting for a couple of weeks.

"The plan is to back away from the Adirondack after we finish the Microscopic
Imager and instrument arm work, take a Pancam of the RAT hole and then
Mini-TES of Adirondack as well," Wallace said.

Spirit was then headed for another rock nicknamed White Boat.

Upcoming for Spirit, the rover will begin the long trek to an impact crater in the
distance. The first day of the trip to Bonneville Crater will extend 20 meters,
setting a new Martian driving record by eclipsing the mark set by Mars
Pathfinder's rover in 1997, Wallace said.

"Sojourner's longest drive was about seven meters."

The Opportunity rover on the other side of Mars, its workdays separated from
Spirit's by 12 hours, continues to function successfully. The sol 14 day that
ended late Saturday morning (U.S. time) saw the rover's arm study a patch of
soil before Opportunity made another small drive.


A view from Opportunity shows the outcrop. Credit: NASA/JPL
 

"We had a very good day," Wallace said. "This was the first 'touch and go' for
the instrument arm on Opportunity. This is where deploy the arm out and we
took microscopic images from several angles of the soil in front of us, then
retracted and stowed the arm and drove nine-tenths of a meter in the forward
direction. It was actually several short moves and a short turn to move about
nine-tenths of meter in the direction of a rock called Snout, which is on the
northeast edge of the outcrop in the Meridiani crater.

"We completed that drive and the post-drive imagery indicated the targets
were within the work volume of the arm."

On the sol 15 day that begins early Sunday morning (U.S time), the arm will be
deployed again to snap several Microscopic Imager pictures of Snout and then
place Mossbauer down on the rock. Late in the day, the Alpha Particle X-Ray
Spectrometer will take over, performing an overnight observation.

Early Monday morning, the arm will be retracted so Opportunity can begin an
arcing drive around the lower edge of the outcrop to survey several points,
Wallace said.

"The science team is deciding how many 'bus stops' we want to hit along the
way. I think the number is varying anywhere between three to six-or-seven.
The total traverse distance is on the order of 30 meters. If we hit five'ish spots,
we are looking at five or six meters per drive."
Received on Mon 09 Feb 2004 12:33:03 AM PST