Engineers still hopeful Mars rover will wake up after dust stormAugust 22, 2018 William Harwood
The Hubble Space Telescope captured this view Mars, with its surface partially hidden under a veil of dust, last month as the planet reached the closest point in its orbit to Earth. Credit: NASA, ESA, and STScI(...) Given the bounty of data already collected during its extended mission, a failure to wake up, while disappointing to its legions of fans, would not be considered a failure in any traditional sense. Few space missions have chalked up a greater record of success, and scientists are hopeful the rover will be able to continue its trail-blazing exploration.
Even though sunlight is believed to be falling once again on Opportunity’s solar arrays, it could take several more weeks to establish contact.
“The problem is, there are still parasitic loads on the electronics,” Callas said. “It’s just like your TV at home. Even though you have your TV turned off, it’s still drawing energy from the outlet. So even though the rover’s powered off, the electronics will still waste energy at a low level.”
Those parasitic loads account for about 40 watt hours of energy. Another 220 watt hours could be going to waste because of an external heater that became stuck on full time early in Opportunity’s mission.
Flight controllers dealt with that problem by putting the rover into “deep sleep” every night to make sure the heater was turned off. Opportunity then woke up each morning thanks to its fully charged batteries.
“It’s kind of like you have a light switch stuck on in your home, so every night you go outside and turn off the master breaker for your house,” Callas said. “That’s kind of like deep sleep on the rover. We turn everything off so that heater goes off.”
But if Opportunity initially lost enough power to trigger a clock fault, “the rover will lose track of time and so it won’t know when to properly deep sleep,” Callas added. “And so it may not be deep sleeping when this heater is stuck on, and so it may be wasting energy that we’re trying to charge the batteries with.”
A clock fault likely developed in the wake of the extended power outage. If so, whenever it wakes up, Opportunity’s computer will reset its clocks to a time in the future and then set timers to trigger communications attempts.
“The rover won’t wake up in the middle of the night, it’ll only wake up during the day, but we won’t know when during the day,” Callas said. “It could be a game of whack-a-mole. It could wake up at one time of day and then we may not hear from it for three days and then wake up at a different time of day.”
To cover those scenarios, NASA’s Deep Space Network, made up of giant antennas used to relay data and commands to spacecraft spread out across the solar system, is “listening” for Opportunity’s call multiple times each weak and at various times of day, covering a broader range of frequencies just to be on the safe side.
Asked how confident he was about Opportunity’s eventual wakeup,
Callas said the odds were better than 50-50.
“Unless we got a whole bunch of dust dumped on the arrays, if we have at least a 50 percent clean array, this vehicle should be charging about now,” he said. “As long as the batteries haven’t gone kaput, and we don’t think they have, this thing should wake up.
“If we haven’t heard (from it) in a couple of months, yeah, then I’m really worried. But I think in the next few weeks, four or five weeks, we should hear something.”
https://spaceflightnow.com/2018/08/22/engineers-still-hopeful-mars-rover-will-wake-up-after-dust-storm/