Spirit Slowly Emerges from Blanket of Dust
Aug. 31, 2007
Spirit remains healthy as the rover slowly picks up more solar energy. The dust storms appear to be over, at least for now, and the skies are slowly clearing. Unfortunately, what energy Spirit has gained from cleaner skies has been offset by losses to dustier solar arrays. Still, Spirit has the energy, about 325 watt-hours, to finally be roving again.
Tau, a measure of atmospheric dustiness, declined slightly. As of Sol 1299 (Aug. 29, 2007), the Sun was at about 8 percent of its full brightness, an increase of a little more than 2 percent compared with five sols earlier. Dust on the rover's solar arrays increased by about 3 percent and only about 59 percent of the sunlight hitting the arrays gets through to make electricity.
But rather than getting a 1-percent boost in solar power, the rover has been just about breaking even. The reason is that Tau measures direct sunlight but there's also scattered sunlight and it, too, increased by about 1 percent.
Much of the dust previously seen on the turret has blown or fallen off. Dust contamination remains a concern, particularly for the microscopic imager, where some of the dust clumps visible in earlier images have fallen out or moved out of the line of sight.
On Sol 1296 (Aug. 25, 2007), Spirit resumed driving to "Home Plate" and more specifically, to a location with gentle slopes and few rocks known as "the on-ramp." This drive was a turn-in-place, given Spirit's frozen right front wheel, to get the rover pointed in the right direction.
After two sols of remote sensing with emphasis on characterizing whatever dust had accumulated on the panoramic camera, Spirit's handlers decided to have the rover retrace its tracks to assess what dust contamination might be present on the miniature thermal emission spectrometer. To do this, they needed to measure a known target.
With a blanket of dust everywhere, scientists needed a way to distinguish dust on targets of scientific interest from dust on the optics. The best target for that was "Gertrude Weise," a patch of nearly pure-silica soil uncovered by Spirit's wheels. Rover planners decided to have the rover drag its wheels through it again to scrape off newly acquired dust and expose the same pure silica as before. Differences between old and new measurements would be due to dust on the instrument itself; once that signature was known, it could be subtracted from future measurements.
The first drive to Gertrude Weise was a little short and didn't uncover the silica as hoped. Spirit's handlers planned a second drive on Sol 1300 (Aug. 30, 2007), during which the rover was to scuff the soil with a half-turn of the left front wheel, then scuff it more by locking both left and right front wheels and driving them backward across Gertrude Weise. They then planned to have the rover back up some more to take images and move toward the Home Plate on-ramp.
Spirit was expected to resume the long-awaited trek to Home Plate on sol 1303 (Sept. 2, 2007).
In addition to daily direct-from-Earth uplinks over the rover's high-gain antenna, relays to Earth at UHF frequences via the Odyssey orbiter, surveys of the sky and ground with the miniature thermal emission spectrometer, measurements of atmospheric opacity with the panoramic and navigation cameras, and image acquisition with the front and rear hazard avoidance cameras, Spirit completed the following activities:
Sol 1295 (Aug. 25, 2007): Spirit conducted remote sensing and acquired panoramic camera images of targets known as "Eileen Dean," "Dorothy Mueller," and "Stealing Third."
Sol 1296: Spirit drove and turned in place 156 degrees to point toward the on-ramp of Home Plate. The rover assessed dust accumulation on the lenses of the panoramic camera and measured atmospheric opacity (Tau) at different times of day.
Sol 1297: Spirit conducted remote sensing and general atmospheric science, including characterizing dust on the panoramic camera.
Sol 1298: Spirit drove, returning to Gertrude Weise.
Sol 1299: Spirit conducted remote sensing and general atmospheric science, including characterizing dust on the panoramic camera.
Sol 1300: Plans called for Spirit to drive, scuff and drag its wheels over Gertrude Weise, and acquire images of the target. The rover was to conduct atmospheric science.
Sol 1301: Plans called for Spirit to conduct remote sensing and general atmospheric science, including characterizing dust on the panoramic camera. The rover was to measure atmospheric argon with the alpha-particle X-ray spectrometer.
Sol 1302 (Sept. 1, 2007): Plans called for Spirit to conduct remote sensing and general atmospheric science, including characterizing dust on the panoramic camera.
As of sol 1298 (Aug. 28, 2007), Spirit's total odometry was 7,169 meters (4.45 miles).
Source: NASA / JPL