“The clock should be the first thing to come back online and start ticking as the batteries charge back up, added Reich. “When the fault response runs, the clock will be re-initialized to that known value stored in its non-volatile memory, but the clock could be reseeded at any time on the sol it wakes up. This would almost certainly cause Oppy to think it’s a different solar time than it actually is and that will affect when she wakes up and whether or not she can talk to Earth.”

The extent of this offset can be on the order of months. “But the real danger is in the difference between what the rover believes is true solar time vs. actual time; for example, is it 09:00 local solar time (LST) or 13:00 LST when it’s actually 10:00 LST?” said Staab.

In any case, an off-set clock would leave Opportunity “so confused” about the time that she never gets a chance to talk to the Earth; consequently, the engineers have never been able to catch the rover with a ‘beep’ command, said Callas. “Or it could be that the rover never had enough power to do a ‘beep’ command because it browns out immediately because it’s not sleeping at the right time.”

If the rover is not DeepSleeping at the right time – that is, nighttime – that could be preventing the rover’s ability to charge up its batteries. It’s “essential” for the rover to be DeepSleeping at night, Callas noted. “We have this stuck-on heater that we’ve had since Sol 1, so if the rover doesn’t DeepSleep at night, then whatever power it charges up during the day is going to get lost to the heater, because that thing is likely going to consume the power we’ve tried to collect, and therefore is undermining the rover’s ability to charge,” he said.

“The clock off-set, coupled with a high Tau/low dust factor, could create this scenario where the rover may only be waking up for a few minutes every sol and just doesn’t have sufficient charge to talk to Earth via the X-band transmitters,” added Staab.

So, in coming sols,the engineers will also try tore-set the clock in the blind, with no data on the ground to tell us what’s happening. The team knows the clock has to have faulted at some point during the last seven and half months.“Maybe that command will get in and the rover will go: ‘Oh gee, I’ve been sleeping at the wrong time,’ and then start to normally sleep, which would allow the batteries to charge,” said Callas.