Spirit Rover Nearly Ready to Roll
January 11, 2004
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.
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," said Amador.
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.
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, said Dr. John
Callas, Mars Exploration Rover science manager at JPL.
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.
Pictures and detailed information from the mission is available
at the project's Web site: http://marsrovers.jpl.nasa.gov.
JPL, a division of the California Institute of Technology,
manages the Mars Exploration Rover project for NASA's Office of
Space Science, Washington.
