Mars Exploration Rover Update - November 5, 2007

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OPPORTUNITY UPDATE: Opportunity Studies Rock Composition and Changes
in
Atmosphere - sol 1316-1321, Nov 05, 2007:
Though atmospheric dust has returned to nearly pre-dust storm levels,
Opportunity's solar arrays are still dustier than before the storm,
keeping power levels about 200 watt-hours lower than pre-storm levels.
Opportunity continues to generate solar power levels of more than 600
watt-hours per Martian day, or sol (100 watt-hours is the amount of
energy required to light a 100-watt bulb for one hour), with the help
of
wind-related cleaning of the solar panels. The spacecraft is healthy.
Opportunity has been studying the so-called "bathtub ring," a light
band
of rock that appears to circle Victoria Crater partway below the
surface. Scientists think the band may be the remains of the original
surface of Meridiani Planum before a meteor blasted out the crater.
The
ring itself appears to have three layers, originally dubbed "alpha,"
"beta" and "gamma" after the first three letters of the Greek
alphabet,
but now renamed "Steno," "Smith" and "Lyell," in honor of pioneering
geologists of the 17th and 18th centuries.
Opportunity is to complete studies of Steno after grinding a hole into
the rock surface with the rock abrasion tool and acquire a final set
of
observations that include measurements with the Moessbauer
spectrometer.
The two spectrometers on Opportunity provide different kinds of
information. The alpha-particle X-ray spectrometer is a general-
purpose
spectrometer that helps determine the chemical composition of the
rocks.
The Moessbauer spectrometer is specifically designed to study
iron-bearing minerals, which are abundant on Mars and give the planet
its red-orange color. Both spectrometers rely on radioactive energy
sources but the one in the Moessbauer spectrometer has a shorter
half-life. That means it gets weaker faster. As a result, Moessbauer
integrations now take longer, typically as many as 60 hours to acquire
useful data. The rover acquires the observations over several sols.
To conserve battery power, which relies on sunlight as a source of
energy, Opportunity sleeps at night. Opportunity happens to have a
heater stuck in the "on" position that draws additional power.
Mechanical thermostats added to the mission just before it was
launched
in 2003 prevent the heater from running during the daytime. But the
heater continues to draw power at night.
Scientists plan to move Opportunity to a second spot on Steno for
continued investigation. Before moving, Opportunity must stow the
robotic arm. If the stow is successful, plans call for the rover to
back
uphill and aim high to compensate for potential slip on the steep
slope
of Victoria Crater before driving forward.
Plans also call for the rover to measure atmospheric argon. Argon is a
trace gas in the Martian atmosphere, comprising about 1.6 percent (the
bulk of the Martian atmosphere is carbon dioxide, the same gas that
gives soft drinks their fizz). Argon is one of the noble gases, so
named
because they don't react chemically with other substances. It is
always
a gas. Water, on the other hand, can be a gas (water vapor), a liquid
(cloud, mists, and rain), or a solid (ice, snow, sleet, and hail).
Water
can also bind physically or chemically to other substances in the air,
such as dusts and soots, smog, and acid rain.
Because argon is always in one physical state (a gas) that is
unadulterated by other substances, it can be used as a barometer. When
atmospheric pressure is high, there's more argon in the field of view.
When it's low, there's less argon. Measurements of the gas with the
alpha-particle X-ray spectrometer track changes in Mar's atmospheric
pressure as a result of changes in global energy flows, dust storms,
and
Mars' position relative to the Sun.
On sol 1320 (Oct. 11, 2007), Opportunity is scheduled to take a series
of nine microscopic images within a minute or two at exactly the same
spot. By adding the pixels (picture elements), engineers can reduce
the
amount of "noise" -- random, microscopic overexposures or
underexposures
-- within the image. Such noise is a constant in nature. By combining
the pixels, engineers can average out the noise to reveal details and
fine texture that would otherwise be obscured.
Sol-by-sol summary:
In addition to daily observations that included measurements of
atmospheric dust with the panoramic and navigation cameras, surveys of
the sky and ground with the miniature thermal emission spectrometer,
and
transfers of data to Earth via the Odyssey orbiter, Opportunity
completed the following activities:
Sol 1316 (Oct. 6, 2007): Opportunity acquired stereo microscopic
images
of Steno, studied the rock's composition with the alpha-particle X-ray
spectrometer, and checked for drift (changes with time) in the
miniature
thermal emission spectrometer.
Sol 1317: Opportunity acquired data from Steno using the Moessbauer
spectrometer, went into a mini-deep sleep, and checked for drift in
the
miniature thermal emission spectrometer.
Sol 1318: Opportunity restarted the Moessbauer spectrometer for
continued
observation of Steno for 24 hours. The rover took thumbnail images of
the sky and a mosaic of images of a target known as "Dolomieu" using
the
panoramic camera. The rover checked for drift in the miniature thermal
emission spectrometer.
Sol 1319: Plans called for Opportunity to restart the Moessbauer
spectrometer for 11 hours of observation of Steno and acquire images
with the panoramic camera as well as check for drift in the miniature
thermal emission spectrometer. The rover was to wake up at 11:20 p.m.
local Mars time to turn off the Moessbauer spectrometer before
returning
to a mini-deep sleep. The following morning, Opportunity was to take
thumbnail images of the sky with the panoramic camera and scan the sky
for clouds with the navigation camera.
Sol 1320: Plans called for Opportunity to take microscopic images of a
hole ground into the surface of Steno with the rock abrasion tool and
spend 23 hours observing the same surface with the Moessbauer
spectrometer. Opportunity was also slated to acquire full-color
images,
using all 13 filters of the panoramic camera, of a target known as
"Arduino" and survey the horizon and take thumbnail images of the sky
with the panoramic camera.
Sol 1321 (Oct. 12, 2007): Plans called for Opportunity to stow the
robotic arm, bump backward a short distance, take images with the
hazard
avoidance camera along the way as well as navigation camera images
after
the drive, and acquire panoramic camera images of the work volume
reachable by the robotic arm. The rover was to acquire post-drive
images
with the navigation camera, unstow the robotic arm, measure
atmospheric
argon with the alpha-particle X-ray spectrometer, monitor dust on the
rover mast, and check for drift in the miniature thermal emission
spectrometer.
Odometry:
As of sol 1321 (Oct. 12, 2007), Opportunity's total odometry remained
at
11,572.94 meters (7.19 miles).
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baalke
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