[meteorite-list] Mars Exploration Rovers Update - March 13-26, 2008

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri, 4 Apr 2008 16:46:53 -0700 (PDT)
Message-ID: <200804042346.QAA20979_at_zagami.jpl.nasa.gov>

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

SPIRIT UPDATE: Spirit Phones Home to Set Clock - sol 1491-1497,
March 13-19, 2008:

Spirit is feeling the strain of juggling activities on Mars in the face
of declining power levels as the winter Sun sinks lower on the horizon.
After acquiring compositional data from a rock target informally named
"Wendell Pruitt," Spirit had to wait a few sols (Martian days) to have
enough energy to conduct atmospheric studies and move the robotic arm
out of the way for a panoramic-camera portrait of a rock target known as
"Freeman." First, the rover had to make a "phone call" to Earth to
correct for drift -- changes in time -- in the spacecraft clock.

When Spirit phones home using a direct-to-Earth, X-band communications
link, the rover's transmitter has to be running, which requires a fair
amount of energy. During more typical, direct-from-Earth communications,
only the rover's receiver has to be on. To set the spacecraft clock,
Spirit transmits a data product called a time packet. The time packet is
used to synchronize the rover's clock back to Earth time (also known as
Universal Time). A previous attempt to relay the time packet was
unsuccessful, causing Spirit's clock to be off by as much as a minute
and a half.

In addition to resetting the clock, Spirit completed a light schedule of
activities on sols 1493-1494 (March 15-16, 2008). By sol 1496 (March 18,
2008), Spirit had generated enough solar power to proceed with
measurements of argon gas in the Martian atmosphere and studies of the
Freeman rock target. Interspersed with those activities, Spirit
continued to work on the "Bonestell panorama" and take panoramic-camera
images of a target dubbed "C.S. Lewis." The rover spent sols 1492, 1494,
and 1497 (March 14, 16, and 19, 2008) recharging the battery, conducting
only minimal science activities, and storing data for later transmission
to Earth.

Spirit continued to have difficulty receiving spacecraft commands via
the rover's high-gain, X-band, dish antenna as a result of the mast that
holds the panoramic and navigation cameras getting in the way and
partially obscuring the signal. To help address this challenge, rover
planners had Spirit complete a self-assessment to see if the rover could
independently recognize an occlusion of the high-gain signal and respond
by swiveling the high-gain antenna to a different position. The
self-assessment, on sol 1493 (March 15, 2008), was successful. Spirit
used the technique prior to an actual uplink session on sol 1496 (March
18, 2008), when the rover's handlers were expecting a particularly
severe occlusion. The activity was successful and the uplink did not
appear to be impeded in any way. Currently, this activity involves
having the rover use a temporary parameter that then goes away when the
rover shuts down for a nap. Rover planners are considering making the
temporary parameter permanent.

Looking forward, Spirit will go increasingly into "hibernate" mode as
the Sun continues to dim. Rover planners predict Spirit will be able to
conduct science activities until about late April.

Spirit is healthy and all subsystems are performing as expected. The
latest available power readings from sol 1496 (March 18, 2008) showed
power at 249 watt-hours (100 watt-hours is the amount of energy needed
to light a 100-watt bulb for one hour). Spirit has no plans to move
before the next Martian spring and is hard at work accomplishing as much
as possible before power levels drop to a point that temporarily
precludes use of the scientific instruments on the rover's arm.

Sol-by-sol summary:

To conserve energy, mission planners have restricted the number of sols
on which Spirit receives direct-from-Earth instructions via the rover's
high-gain antenna and transmits data to Earth via the Odyssey orbiter.
Spirit continues, on a daily basis, to monitor atmospheric dust levels
with the panoramic camera, check for drift (changes with time) in the
miniature thermal emission spectrometer, and survey the sky and ground
with the instrument. In addition, during the past week, Spirit completed
the following activities:

Sol 1491 (March 13, 2008): After communicating with Odyssey, Spirit
studied the elemental composition of "Wendell Pruitt" with the
alpha-particle X-ray spectrometer.

Sol 1492: In addition to monitoring atmospheric dust and conducting
surveys with the miniature thermal emission spectrometer, Spirit
recharged the battery.

Sol 1493: Spirit initiated a direct-to-Earth communications link using
the X-band antenna and transmitted a data packet to correct the
spacecraft clock.

Sol 1494: In addition to monitoring atmospheric dust and conducting
surveys with the miniature thermal emission spectrometer, Spirit
recharged the battery.

Sol 1495: In the morning, Spirit acquired column 3, part 1 of the
full-color Bonestell panorama, using all 13 filters of the panoramic
camera. Spirit positioned the alpha-particle X-ray spectrometer to
measure argon gas in the Martian atmosphere. The rover took a
single-frame image with the navigation camera. After communicating with
Odyssey, Spirit measured argon with the alpha-particle X-ray spectrometer.

Sol 1496: Spirit monitored dust accumulation on the rover mast and
acquired column 3, part 3 of the full-color Bonestell panorama. The
rover acquired full-color images, using all 13 filters of the panoramic
camera, of the Freeman rock target.

Sol 1497 (March 19, 2008): Spirit looked for changes in the "El Dorado"
dune field with the panoramic camera and acquired column 4, part 1 of
the Bonestell panorama. The rover recharged the battery. The following
morning, Spirit was to acquire movie frames in search of clouds with the
navigation camera, acquire super-resolution, panoramic-camera images of
a target dubbed "C.S. Lewis half," and survey the horizon with the
panoramic camera.

Odometry:

As of sol 1496 (March 18, 2008), Spirit's total odometry was 7,528
meters (almost 4.7 miles).

------------------------------------------------------------------------

OPPORTUNITY UPDATE: Opportunity Completes Dental Checkup - sol
1478-1483, March 21-26, 2008:

Opportunity is wrapping up its scientific investigation of the outcrop
exposure known as "Gilbert_A" at the bottom of the alcove known as "Duck
Bay," the lowest traversable portion of the crater's interior. Duck Bay
is a recess in the walls of "Victoria Crater."

Opportunity performed a dental self-examination of teeth in the rover's
rock abrasion tool on Sol 1482 (March 25, 2008). Images of the grinding
bit, taken with the hazard avoidance cameras, showed no appreciable wear
since the last measurement on sol 1443 (Feb. 14, 2008). In fact, the
rover's handlers saw a slight increase rather than decrease in bit
height, highlighting the uncertainty inherent in the bit measurement
technique. Indeed, the calculated 32 percent of grinding material left
is subject to a 39-percent relative error, resulting in an absolute
error of 12 percent (based on a statistical calculation, 0.32 * 0.39 =
12). Unfortunately, there is no clear way to reduce the error in bit
measurement.

Opportunity is healthy and all subsystems are operating as expected.
Energy is currently around 360 watt-hours (100 watts is the amount of
energy needed to light a 100-watt bulb for 1 hour). Tau measurement of
opacity caused by atmospheric dust is 0.68 (a Tau of zero would
correspond to a perfectly clear sky). The dust factor is 0.679, meaning
that about 68 percent of sunlight reaching the solar arrays penetrates
the coating of dust to generate electricity.

Next week, Opportunity is scheduled to drive toward the promontory known
as "Cape Verde" for a better look at the rocks exposed in the crater walls.

Sol-by-sol summary:

In addition to receiving morning instructions directly from Earth via
the rover's high-gain antenna, relaying data to Earth each evening via
the UHF antenna on the Mars Odyssey orbiter, and completing atmospheric
observations that included measuring atmospheric dust with the panoramic
camera, monitoring dust accumulation on the rover mast, and scanning the
sky for clouds with the navigation camera, Opportunity completed the
following activities:

Sol 1478 (March 21, 2008): Opportunity spent 12 hours acquiring data
from Gilbert with the Moessbauer spectrometer. The rover completed a
survey at high Sun with the panoramic camera and went into a mini-deep
sleep.

Sol 1479: Opportunity spent 12 hours acquiring data from Gilbert with
the Moessbauer spectrometer. The rover took thumbnail images of the sky
for calibration purposes with the panoramic camera and went into a
mini-deep sleep.

Sol 1480: Opportunity spent 5 hours acquiring data from Gilbert with the
Moessbauer spectrometer and took full-color images, using all 13 filters
of the panoramic camera, of the backslope to the left of the Gilbert
area. The rover acquired images of the rock target dubbed "Lyell Oxford"
and surveyed the horizon with the panoramic camera. The rover went into
a deep sleep.

Sol 1481: Opportunity spent 7 hours acquiring data from Gilbert with the
alpha-particle X-ray spectrometer and took images of Lyell Oxford with
the panoramic camera. The rover took six movie frames spaced at regular
intervals in search of clouds with the navigation camera and went into a
mini-deep sleep.

Sol 1482: Opportunity took a microscopic image of the hole ground into
Gilbert with the rock abrasion tool and completed a survey of the
grinding bit on the tool. Opportunity spent 8 hours integrating data
from Gilbert with the Moessbauer spectrometer and went into a mini-deep
sleep.

Sol 1483 (March 26, 2008): Opportunity spent 7 hours integrating data
from Gilbert with the Moessbauer spectrometer and went into a deep sleep.

Odometry:

As of sol 1483 (March 26, 2008), Opportunity's total odometry was
11,671.23 meters (7.25 miles).
Received on Fri 04 Apr 2008 07:46:53 PM PDT