A cleaning event is a phenomenon whereby dust is removed from solar panels, particularly ones on Mars, by the action of wind. The term cleaning event is used on several NASA webpages; generally the term is used in reference to the fact that Martian winds have blown dust clear of the solar panels of probes on Mars increasing their energy output.[1]
The term started being used in 2004 as the Mars Exploration Rovers' solar panels started to benefit from these events. The rovers were expected to last about 90 sols (Martian days) on Mars, after which dust would cover their solar panels and reduce solar power to levels too low for the rovers to operate. However, power levels went back up due to the cleaning events caused by the winds in the Martian atmosphere. Periodic cleaning events have allowed the MER rovers to operate for several years, rather than the planned 3 months.
Cleaning events can either be rapid, such as overnight, or over many days where solar power slowly goes up.[2] For example, the MER-A Spirit rover, on April 18, 2009 and April 28, 2009 the power output of the solar arrays were increased by cleaning events.[3][4] The power output of Spirit's solar arrays increased from 223 watt hours per day on March 31, 2009 to 372 watt hours per day on April 29, 2009.[4]
Other factors that affect solar power output include the opacity of the Martian atmosphere and Martian seasonal changes.
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