Spirit Rover Gets Power Windfall

Feb 18, 2009
By Aerospace Daily & Defense Report



Controllers driving the Spirit Mars Exploration Rover will get some extra mileage in the coming weeks as it continues the search for silica deposits, following an apparently fortuitous wind that blew accumulated dust off its solar arrays.

Fresh off a troublesome loss of control in January (Aerospace DAILY, Feb. 6), Spirit's operators at the Jet Propulsion Laboratory (JPL) noted a 30-watt-hour increase in Spirit's power supply, which they believe is the result of lower dust accumulation on the arrays that generate the rover's electricity.

The increase gives Spirit about 240 watt-hours a day to work with, up from about 210. Overall the rover needs about 180 watt-hours per day for "basic survival" and communications, which means the amount of power available above that has roughly doubled.

"We will be able to use this energy to do significantly more driving," said JPL's Colette Lohr, a rover mission manager. "Our drives have been averaging about 50 minutes, and energy has usually been the limiting factor. We may be able to increase that to drives of an hour and a half."

Last month Spirit failed to respond to the daily driving commands radioed from JPL, setting off a round of testing and diagnostics that led mission managers to conclude a cosmic-ray hit had probably shut down the rover's flash memory. With the memory temporarily out of commission, the rover couldn't store the commands.

Tests also suggested Spirit's accelerometers were probably off by about 3 degrees, skewing its orientation on the surface.

Since the end of January the rover has been moving again, looking for high concentrations of silica to the north away from the "Home Plate" feature. Scientists believe such deposits may be evidence of ancient steam vents or hot springs.

Controllers first noticed the extra power on Feb. 6, and quantified it over the following two days. They believe that the wind cleaning boosted the amount of sunlight penetrating dust on the arrays from 25 percent to 28 percent.

Spirit and its twin Opportunity have been operating on the surface for more than five years, even though they were originally planned for a three-month nominal service life there.

Artist's concept of Mars Exploration Rover: NASA