[meteorite-list] Mars Exploration Rover Update - November 1, 2007

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri, 2 Nov 2007 09:19:21 -0700 (PDT)
Message-ID: <200711021619.JAA29545_at_zagami.jpl.nasa.gov>

http://marsrovers.jpl.nasa.gov/mission/status.html#opportunity

OPPORTUNITY UPDATE: Opportunity Studies "Bathtub Ring" In "Victoria
Crater" - sol 1301-1308, Nov 01, 2007:

Opportunity is healthy, with energy levels ranging from about 450
watt-hours to 475 watt-hours (100 watt-hours is the amount of
electricity needed to light a 100-watt bulb for one hour).

Recently, Opportunity was temporarily unable to send scientific data to
Earth because the Odyssey orbiter experienced a computer crash and went
into "safing" mode. While in safing mode, the spacecraft shuts off
unnecessary power loads, orients itself for maximum sunlight to the
solar arrays, switches to communication modes most likely to receive
commands from Earth, and basically stops all unnecessary activity while
waiting for the folks back home to fix it and put it back in service.

While in safing mode, Odyssey did not send communications from either
Mars rover. Opportunity continued to collect as much science as possible
while waiting for Odyssey to be fixed.

After Odyssey was back in service, Opportunity began making up for lost
time. Following a series of "toe dips," during which the rover drove a
short way into "Victoria Crater" and backed out again, then drove a
little farther and backed out again, Opportunity began examining the
crater's interior.

Victoria Crater is interesting because it affords a chance to study rock
layers down to a depth of about 70 meters (230 feet) below the
surrounding surface. The modern surface isn't the original surface -- it
has been altered by an incoming meteor. When a meteor strikes, it throws
up a huge amount of debris that falls back around the crater and creates
an "ejecta blanket." This blanket is thickest near the crater rim and
thinnest farther away from the crater.

Below Victoria's raised rim is a light-colored band nicknamed the
"bathtub ring." Scientists hypothesize that this band is the dividing
line between the original surface and the ejecta blanket above it.
Opportunity has now reached this area -- but not without difficulty.

To reach the ring, Opportunity drove across a slope of about 25 degrees,
nearly the maximum allowable tilt for the rover. The rover approached
the ring on sol 1302 (Sept. 22, 2007) and then partially drove and
partially slipped into closer position. On sol 1305 (Sept. 25, 2007),
the rover unstowed the robotic arm and began studying the rocks that
make up the top, or "Alpha," layer of the ring. Below that are two more
layers, known as "Beta" and "Gamma," respectively.

Halfway through the last short drive of about 20 centimeters (8 inches),
Opportunity automatically stopped when the rover violated the tilt
limit. As a result, the rover drove laterally about 10 centimeters (4
inches) and then slid downslope 10 centimeters (4 inches). Subsequent
analysis suggested that one of the downslope wheels rolled off a slight
curb, producing a jolt that caused the rover to slip. Images showed that
the rover had stopped on a hard outcrop of rock rather than sand or soil
and was unlikely to slip farther.

Given the steep slope, Opportunity was extremely careful about moving
the robotic arm. Before placing it on Alpha Layer, Opportunity moved the
arm out, to the left, and to the right, while also checking for any
vehicle motion with both the inertial measurement unit and cameras. The
first rock target was dubbed "Steno."

Opportunity continued to conduct untargeted remote sensing by, among
other things, measuring Tau, or atmospheric opacity, several times each
Martian day, or sol. Now that the dust storms are over, the dust is
settling. How fast it settles is of both scientific and engineering
interest because it affects solar energy levels. Opportunity also
periodically checked deposition and movement of dust on the panoramic
camera mast assembly and solar arrays. This provides data for estimating
wind directions and speeds, dust particle sizes, and dust composition.

Opportunity performed two "Quick Fine Attitude" checks. These are
calibration activities that compensate for drift, or changes in time, in
the inertial measurement unit. The unit uses gyroscopes and
accelerometers to estimate the rover's motion, from which its position
can be calculated. However, the gyroscopes show a slight change in
attitude while the rover is still. (Older, mechanical gyroscopes drifted
because of friction; newer, electronic gyroscopes drift for more complex
reasons.)

The attitude checks compute where the sun should be based on the current
time and the rover's movement and then compares this to the actual
location of the sun in images from the panoramic camera. The difference
forms the basis of the attitude correction for the rover.

Sol-by-sol summary:

In addition to daily observations that included frequent measurements of
atmospheric dust with the panoramic and navigation cameras, surveys of
the sky and ground with the miniature thermal emission spectrometer, and
checks for drift (changes with time) in the miniature thermal emission
spectromeer, Opportunity completed the following activities:

Sol 1301 (Sept. 21, 2007): Opportunity acquired panoramic camera images
of the foreground, checked for drift in the miniature thermal emission
spectrometer, checked the operation of the spectrometer, and surveyed
the rover's external calibration target with the spectrometer. Before
going into a deep sleep, the rover surveyed the horizon at low sun with
the panoramic camera. The next morning, Opportunity monitored dust on
the rover mast.

Sol 1302: Opportunity stowed the robotic arm, drove toward Alpha Layer,
acquired images with the hazard avoidance cameras just prior to and
after completing the drive, and completed a "quick fine attitude" update
to confirm the rover's exact location. The rover unstowed the robotic
arm, acquired post-drive images with the navigation camera, and acquired
panoramic camera images of the work volume (the area reachable by
instruments on the robotic arm). After that, Opportunity went into a
deep sleep.

Sol 1303: Opportunity assessed the external calibration target with the
miniature thermal emission spectrometer, recalibrated the panoramic
camera, and spent six hours measuring atmospheric argon with the
alpha-particle X-ray spectrometer. The rover went into a mini-deep sleep.

Sol 1304: Opportunity surveyed the external calibration target with the
miniature thermal emission spectrometer, recalibrated the panoramic
camera, and went into a deep sleep. The next morning, the rover took
spot images of the sky with the panoramic camera.

Sol 1305: Opportunity stowed the robotic arm, bumped (drove a short
distance) to Alpha Layer, and acquired penultimate and ultimate images
with the hazard avoidance cameras. The rover completed a "quick fine
attitude" check, acquired panoramic camera images of the work volume,
unstowed the robotic arm, and acquired post-drive navigation camera
images. Opportunity recalibrated the panoramic camera and went into a
deep sleep.

Sol 1306: Opportunity acquired data from the external calibration target
with the miniature thermal emission spectrometer and recalibrated the
panoramic camera.

Sol 1307: Opportunity completed a "quick fine attitude" check, conducted
a safety test with the robotic arm, acquired left-eye images of the
alpha-particle X-ray spectrometer with the panoramic camera, and
acquired stereo images of Steno with the microscopic imager. The rover
placed the alpha-particle X-ray spectrometer on Steno and, after
relaying data to Odyssey and recalibrating the panoramic camera,
collected data from Steno with the spectrometer for 12 1/2 hours.

Sol 1308 (Sept. 28, 2007): After the usual dust monitoring and imaging
activities as well as data relays to Odyssey, Opportunity went into a
deep sleep.

Odometry:

As of sol 1308 (Sept. 28, 2007), Opportunity's total odometry was
11,572.94 meters (7.19 miles).
Received on Fri 02 Nov 2007 12:19:21 PM PDT