January 11, 2004
Rover Readying
to Roll
NASA's Spirit rover now has its arm and
all six of its wheels free, and only a single cable must be cut
before it can turn and roll off its lander onto the soil of Mars.
As that milestone is completed, scientists are taking opportunities
to take extra pictures and other data.
During the past 24 hours -- the rover's
8th martian day on the planet, or "sol 8" -- pyro devices
were fired slicing cables to free the rover's middle wheels and
releasing pins that held in place its instrumented arm. The arm
was then locked onto a hook where it will be stowed when the
rover is driving.
Because one airbag remains adjacent to
the lander's forward ramp, the rover will turn about 120 degrees
to its right and exit the lander from the side facing west-northwest
on the planet -- also the direction of an intriguing depression
that scientists have dubbed Sleepy Hollow.
Spirit's Planned Roll Off
Route
Click
for larger image
Courtesy NASA/JPL
Current plans call for the rover to complete
that turn in three steps, said Arthur Amador, one of the mission
managers at NASA's Jet Propulsion Laboratory, Pasadena, Calif.
As currently envisioned, during the coming martian day engineers
will complete ground tests and execute dress rehearsals of the
drive-off, or "egress."
On sol 10 -- the night of Monday-Tuesday,
Jan. 12-13, California time -- engineers expect to sever the
umbilical cord that connects the rover to its lander by firing
a pyro device, the last of 126 pyro firings since Spirit separated
from its cruise stage shortly before landing on Jan. 4 (Jan.
3 in U. S. time zones). Also on that day, the rover will execute
the first of three parts of its turn when it moves clockwise
(as viewed from above) about 45 degrees.
After taking and analyzing pictures to
verify the first part of the turn, engineers anticipate completing
it on sol 11 (night of Tuesday-Wednesday, Jan. 13-14). First,
the rover will turn an additional 50 degrees and stop to take
pictures. Then, if all is well, it will turn a final 20 to 25
degrees to position it precisely in front of one of its three
exit ramps.
If no issues crop up as those steps are
completed, the rover could drive off onto the martian soil no
earlier than sol 12 (night of Wednesday-Thursday, Jan. 14-15).
"But we adjust our schedule every day, based on flight events,
so this remains an estimate," said Amador.
The rover's status overall is "pretty
darn perfect," Amador said. He described the communication
link from Mars to Earth as excellent, allowing the team to receive
170 megabits of data during the past day. All science data stored
on the rover has been sent to Earth. The rover is generating
900 watt-hours of power per day and using 750 watt-hours, and
its thermal condition is good, he added.
Rover Roll Off Test on Earth
Click
for larger image
Courtesy NASA/JPL
While engineers are completing and testing
commands to execute the rover's turn and egress, the science
team is enjoying an "unexpected dividend" of time to
collect data, Dr. John Callas, Mars Exploration Rover science
manager at JPL, said.
Until now, all science observations have
been planned far in advance, but the unfolding schedule of rover
activities gave the team the opportunity to do their first on-the-fly
planning for observations driven by previous results, Callas
explained. In doing so they segued to a working style that they
will practice on a day to day basis as the rover rolls across
the surface of its landing site in Gusev Crater, named the Columbia
Memorial Station.
In the next 24 hours, the team will collect
270 megabits of science data, considerably more than on any previous
martian day. This will include a high-quality, 14-color mosaic
taken by the panoramic camera of a third of the horizon toward
Sleepy Hollow, the direction in which the rover will leave its
lander.
In addition, they plan to complete two
remaining "octants" (each a pie slice showing an eighth
of the horizon) with the rover's miniature thermal emission spectrometer.
These areas will also be rephotographed with the rover's panoramic
camera in order to allow the camera and spectrometer data to
be co-registered. Plans also call for the spectrometer to "stare"
at three selected sites to collect very low-noise data, as well
as calibration of another science instrument, the alpha particle
X-ray spectrometer.
Spirit's twin Mars Exploration Rover, Opportunity,
will reach Mars on Jan. 25 (Universal Time and EST; Jan. 24 PST).
The rovers' main task is to spend three months exploring for
clues in rocks and soil about whether the landing sites may have
had abundant water for long enough in the past for life to appear.
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Extends Wheels and Sends More Photos
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