* Astronomy

SPIRIT UPDATE: Spirit Finally Reaches a Potential Winter Haven - sol 803-811, Apr 14, 2006:

Spirit is basking in the sun, relatively speaking, on a 10.8-degree, north-facing slope in Gusev Crater on Mars. After turning away from the rover's previous heading toward "McCool Hill" last week, Spirit started driving toward a nearby area known as "Low Ridge Haven" and arrived there over the weekend. Because rover drivers were able to get Spirit to a place where the solar panels tilt more steeply toward the sun, the rover's power output increased by 50 to 60 watt-hours per sol. That gives the rover enough energy for about one hour of daytime remote science.

So far in this location, Spirit has collected a 360-degree panorama with the navigation camera, a smaller panorama with the panoramic camera, two targeted observations with the miniature thermal emission spectrometer, and five targeted images with the panoramic camera. Spirit also collected data with instruments on the robotic arm, including the microscopic imager, the alpha particle X-ray spectrometer, and the Mössbauer spectrometer. All the rock and soil targets in this area are being informally named after Antarctic research stations and explorers.

Sol-by-sol highlights:

Sol 803 (April 6, 2006): Spirit drove about 9 metres closer to "Low Ridge Haven," approaching a break in the north-facing slopes of the small outcrop.

Sol 804: Spirit recharged the batteries and conducted atmospheric remote sensing.

Sol 805: Spirit spent as much of the weekend as possible driving toward a north-facing slope to allow the rover's solar panels to soak up more energy from the sun. After advancing slightly more than 10 metres, Spirit ended up in a nice, sunny spot, with a northerly tilt of 10.8 degrees.

Sol 806: Spirit recharged the batteries and used the panoramic camera to view the surrounding terrain from the new location reached by the sol 805 drive.

Sol 807: Spirit's weekend drive placed the rover at a potentially safe place to spend the winter on Mars. Activities included a "get fine attitude," a procedure completed every couple of weeks to correct any error in the rover's knowledge of its attitude relative to the sun. (Between updates, the rover uses the onboard computer to keep track of attitude changes, but error builds up in this measurement over time.) The rover also used the navigation camera and panoramic camera for additional and higher-resolution images of the terrain surrounding the current location.

Sol 808: Spirit observed rock targets called "Marambio" and "Orcadas" using the miniature thermal emission spectrometer and collected images of a target called "Maitri" using the panoramic camera.

Sol 809: Spirit deployed the robotic arm for the first time since the week of sols 769 to 772 (March 2 to March 5, 2006), when the rover conducted scientific observations near "Home Plate." Spirit acquired microscopic images of a target called "Halley" and completed an overnight analysis with the alpha particle X-ray spectrometer. The rover also acquired panoramic-camera images of "Troll" and "Mirny."

Sols 810-811 (April 13-14, 2006): Plans for the weekend called for continued work on "Halley," including measurements with the Moessbauer spectrometer, and targeted remote sensing, including panoramic camera images of "Orcadas" and "Marambio."

Odometry:
As of sol 811 (April 14, 2006), Spirit's total odometry was 6,876.18 metres.

Sol 810

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Spirit is in Mars' Southern Hemisphere, where the sun is crossing lower in the northern sky each day. The rovers rely on solar power. The amount available will keep dropping until the shortest days of the Mars winter, four months from now.
To keep producing enough electricity to run overnight heaters that protect vital electronics, Spirit's solar panels must be tilted toward the winter sun by driving the rover onto north-facing slopes. However, on March 13 the right-front wheel's drive motor gave out. Spirit has subsequently driven about 80 meters using five wheels and dragging the sixth, but an initial route toward a large hill proved impassable due to soft ground. Last week, the team chose a smaller nearby ridge, dubbed "Low Ridge Haven," as the winter destination.
Spirit reached the ridge on Sunday and has a favourable 11-degree tilt toward the north.

"We have to use care choosing the type of terrain we drive over" - Dr. A****ey Trebi-Ollennu, a rover planner at NASA's Jet Propulsion Laboratory, Pasadena, California.

In tests at JPL, the team has been practicing a manoeuvre to gain additional tilt by perching the left-front wheel on a basketball-size rock.

Spending eight months or so at Low Ridge Haven will offer time for many long-duration studies that members of the science team have been considering since early in the mission. These include detailed mapping of rocks and soils; in-depth determination of rock and soil composition; monitoring of clouds and other atmospheric changes; watching for subtle surface changes due to winds; and learning properties of the shallow subsurface by tracking surface-temperature changes over a span of months.

The Mars rover Spirit, hampered by a broken wheel, has failed to reach its destination and will spend the Martian winter at an alternate site.

Sol 807

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This photo shows the slope called Low Ridge where Spirit will spend the winter and use the sun to power its solar panels.
Credit: Caltech/Cornell

Spirit was initially headed toward a layered rock outcrop known as "Korolev," to the east of the rover's current position, when the wheels began experiencing a high rate of slippage.
Spirit drove back downhill and began a different trek toward a slope that will provide maximum sunlight--and thus power--to survive the martian winter. (On the other side of Mars and nearer to the martian equator, Spirit's twin Opportunity does not face the same power concerns.)