EXPLORE


JOINRENEWJOIN

Give a Gift Membership
  

Planetary News: Mars (2007)

The Mars Exploration Rovers Rove Out of Dust Storms

By A.J.S. Rayl
August 29, 2007

Mars Exploration Rover
Click to enlarge >
Mars Exploration Rover
Mars Exploration Rover Color: True color. Credit: NASA / JPL / Maas

The Mars Exploration Rovers -- Spirit and Opportunity -- have survived the dust storms that whipped up and spread around the planet during the last couple of months and are now getting back to regular work schedules and doing what they do so well -- roving.

"Weather and power conditions continue to improve, although very slowly for both rovers," John Callas, MER project manager at the Jet Propulsion Laboratory (JPL), announced late last week.

No new storms have been lifting dust into the air near either solar-powered rover in the past two weeks and the skies are gradually brightening above both Spirit and Opportunity. The clearing, however, "could take months," noted JPL's Bruce Banerdt, MER project scientist. "There is a lot of very fine material suspended high in the atmosphere."

With the improved energy, both rovers are back on schedule to communicate daily. For several weeks, Opportunity was conserving energy by only communicating a couple of times a week.

After six weeks of hunkering down during darkened skies that reduced and limited solar power, Opportunity drove 13.4 meters (44 feet) toward the edge of Victoria Crater on August 21. MER mission controllers were taking advantage of gradual clearing of dust from the sky while also taking precautions against buildup of dust settling onto the rover.

One reason the rover team chose to drive Opportunity closer to the crater rim was to be prepared, if the pace of dust accumulation on the solar panels increases, to drive onto the inner slope of the crater. This would allow the rover to tilt its solar arrays to the Sun to maximize its intake of the solar power. The drive was also designed to check performance of the rover's mobility system, and it included a turn in place and a short drive backwards.

As the dust settles out of the air, it's accumulating on surfaces such as the rovers' solar panels and instruments. More dust on the solar panels lessens the panels' capacity for converting sunlight to electricity, even while more sunlight is getting through the clearer atmosphere.

But Opportunity got a break the day – or sol -- after its drive when a favorable gust whisked some dust from its solar panels, providing a boost of about 10 percent in electric output, forestalling the need to hurry to a Sun-facing slope. Its power level reached nearly 300 watt-hours on August 23, more than twice as much as five weeks ago, still less than half as much as two months ago. The team is anxious to get Opportunity inside Victoria Crater to check out a host of new science targets on the inner slope that were chosen in June, shortly before dust storms stopped the rover in its tracks. But just how soon the rover will enter the crater depends on assessments of how dust may be affecting the instruments and of how much energy will be available.

Spirit, meanwhile, has been faring well, although dust accumulation on its solar arrays has offset the would-be gain from clearing skies. Currently, Spirit's energy levels are about the same as Opportunity's, around 300 watt-hours per day.

Last Thursday, Spirit, which has been meticulously continuing it examination of a high silica rock called Innocent Bystander this month, drove 42 centimeters (17 inches) backwards to get in position for taking some final images of it. The rover team is planning additional drives for it to climb onto the raised volcanic formation called Home Plate.

The "injuries" sustained by the rovers during the dust storms is as yet undetermined. It appears that there is some dust on the lens of the microscopic imager on Spirit. That has slightly reduced image quality for that instrument, although image calibration can compensate for most of the contamination effects. The team is experimenting with ways to try dislodging the dust on the lens.

A complete report on the adventures and activities of Spirit and Opportunity this month, will be posted on Friday, August 31, 2007 in the Mars Exploration Rover Update.