STORY WRITTEN FOR CBS NEWS AND USED WITH PERMISSION
Flight leaders have not heard from NASA & # 39; s Opportunity Mars rover since June 10, when an increasingly heavy global dust storm blocked the sun, preventing the solar panels from charging the robot's batteries. But the dust storm eventually decreases and engineers hope that the long-living rover will wake up in the next few weeks and call home.
"The weather has improved on Mars," said project manager John Callas at NASA's Jet Propulsion Laboratory in Pasadena, California. "So the atmospheric coverage on the rover site is falling."
This opacity, a measure of how effectively suspended dust blocks the sunlight, climbed to record levels when the storm developed in June. A major dust storm in 2007 had an opacity level or tau above 5.5, while the current storm had an estimated tau of almost 11 on 6 June.
It is now back to a tau of about 2, "begins to approach a range where energy needs to be generated by the solar panels," Callas said in an interview with CBS News. "So we're starting to get close to the timeframe where the vehicle has to start charging, we're looking every day, people are betting about when they think we'll hear about it."
But it is not certainty.
Mars is now past its point of closest approach to the sun in its two-year orbit, and the dust storm, which has kept the atmosphere warmer than usual, is decreasing. As time passes, the temperatures at the Opportunity location will drop, threatening the electronics of the rover and other temperature sensitive systems in the absence of power to make the heating work.
Nevertheless, Callas indicated that a detailed analysis of the rover's systems shows that it should have survived its test by dust. It is just a question of building up enough cargo to wake up, go through the error programming and try to connect with the earth.
"I think everyone is staying closer to their email and their mobile phones right now because we think it's important now when we hear something," Callas said.
The Opportunity Story is an unlikely story about exploration and scientific success by a spacecraft that lasts only 90 days and still lives, albeit with a variety of age-related ailments, for more than 14 years since returning to airbagged airbags landing in January 2004.
Given the wealth of data collected during the extended mission, failure to wake up, although disappointing for its legions of fans, would not be considered a failure in any traditional sense. Few space missions have been more successful and scientists hope that the rover can continue his groundbreaking exploration.
Although it seems that the sunlight falls again on the Opportunity solar panels, it may take a few weeks before contact is made.
"The problem is that there are still parasitic loads on the electronics," Callas said. "It's like your TV at home – even if you've turned off your TV, it still takes energy from the wall socket, so even if the rover turns off, the electronics still waste energy at a low level."
These parasitic loads provide about 40 watts of energy. A further 220 watt hours could be lost due to an external heating that was full-time early in the Opportunity mission.
Flight leaders tackled that problem by putting the rover into deep sleep every night to make sure the stove was switched off. The opportunity then woke up every morning thanks to the fully charged batteries.
"It is as if you have glued a light switch on your house, so you go outside every night and take out the master breaker for your house," Callas said. "That's a kind of deep sleep on the rover, we'll turn everything off so that the stove goes out."
But if Opportunity initially lost enough power to activate a clock error, "the robber loses sight of the time and does not know when to sleep well," Callas added. "And so it may be that it is not deeply dormant when this stove is stuck, and so it can waste energy with which we try to recharge the batteries."
A clock error that probably occurred after the power outage failed. If so, the Opportunity computer will reset its clocks every time they wake up to a time in the future and then set timers to activate communication attempts.
"The rover does not wake up in the middle of the night, he only wakes up during the day, but we do not know when he is during the day," Callas said. "It could be a game crazy, it could wake up at some time of the day and then we might not hear it for three days and then wake up at another time."
To cover that scenario, NASA's Deep Space Network, consisting of giant antennas that are used to transmit data and commands to spacecraft scattered across the solar system, "listens" to Opportunity & # 39; s call multiple times, each weak and at different times of the day a wider frequency range to ensure the certainty.
When asked how certain he was about the possible awakening of Opportunity, Callas said the odds were better than 50-50.
"Unless we have dumped a lot of dust on the series, if we have at least a 50 percent clean row, this vehicle should be loading now," he said. "As long as the batteries have not broken, and we think they are not, this thing should awaken.
"If we have not heard it (within a few months), yes, then I'm really worried, but I think we should hear something in the coming weeks, four or five weeks."