[/caption]Just when we were growing concerned that we might be losing two Mars surface missions within a week of each other, it turns out Mars Exploration Rover Spirit has survived its recent run-in with a Sun-dimming dust storm. On Tuesday, Nancy reported that Spirit had generated a record low power output from its solar panels, indicating the storm could drive Spirit’s energy levels to a point where an emergency fail-safe would switch the wheeled robot into a sunlight-deprived coma. Mission controllers sent Spirit commands to shut down non-essential instrumentation and instructed it not to communicate with NASA until today.
It would appear the rugged rover weathered the storm, expertly avoided a low-power fault and after four days of silence, sent the signal to NASA just as it was told to do. What an incredible little robot…
One might think that using solar panels to collect light on a planet where Sun-blocking dust is a problem is a bit silly. After all, it seems the Phoenix Mars lander succumbed to an arctic dust storm-induced drained battery, and Spirit was also hit by the solar panel’s old foe, a dust storm in Gusev Crater. But the key point that needs to be remembered in both cases is that these missions operated far beyond their expected lifespan. Phoenix was only supposed to be digging into the Martian dirt for three months (it lasted five months), plus the lander had a pretty tough deadline to keep to: the loss of sunlight and the freezing cold of the onset of the northern winter. Phoenix knew its fate, but it was able to push into the dark and cold for a little longer…
However, Spirit’s fate was far from sealed. Usually the rover enjoys a full sol of daylight, day and night as regular as clockwork. This is another piece of NASA engineering that has surpassed every expectation there is. I doubt that any scientist would have said that a mission designed to operate for only three months, would be roving the Martian surface nearly five years later! So already, every minute Spirit (and its twin rover Opportunity on the other side of the planet) spends transmitting data from the Red Planet is a huge bonus.
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However, MER scientists were not going to let Spirit drop dead due to a flat battery. When NASA realised Spirit was beginning to suffer, drawing much less power than was needed from its solar panels, action was taken. Firstly, some heaters were switched off (one heater protects the thermal emission spectrometer instrument from the cold), and Spirit was put on a strict low-energy consumption routine. This routine meant commanding Spirit not to attempt to communicate with Earth for four days, which was probably the most nerve-racking measure that could be taken; once communication is severed, who’s to say we’d ever hear from the rover again?
Even though engineers had stopped Spirit from communicating, they continued to listen, just in case Spirit dropped into a low-energy shutdown mode. However, no signal was received until today (Thursday), right when Spirit was scheduled to phone home. At mission control at JPL in Pasadena, CA, NASA engineers shouted “she’s talking,” when they got word that Spirit had made contact.
Although her batteries are low, the rover is still working and talking with NASA. Let’s hope Spirit holds on for a while longer…