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Air traffic controllers have not heard of NASA's Opportunity Mars rover since June 10, when increasingly heavy global dust blocked the sun and prevented the solar cells from charging the robot's batteries. But the dust storm is coming to an end, and the engineers hope that the long-lived Rover will wake up in the coming weeks and call home.
"The weather has improved on Mars," said Project Manager John Callas at NASA's Jet Propulsion Laboratory in Pasadena, California. "That's how the atmospheric opacity on the rover's terrain decreases."
This opacity, a measure of how effectively hovering dust blocks sunlight, climbed to record highs as the storm developed in June. A large dust storm of 2007 had an opacity level, or tau, above 5.5, while the current storm had an estimated dew of nearly 11 on June 6.
It's now back to about a dew of about 2, "An area where the solar panels should be generating energy is approaching," Callas said in an interview with CBS News. "We are slowly approaching the timeframe when the vehicle should start charging, we search every day, people make bets when they think we'll hear about it."
But it's not a safe bet.
Mars has now passed its point of approaching the Sun in its two-year orbit, and the dust storm, which has kept the atmosphere warmer than usual, is dwindling. Over time, temperatures at the Opportunity site will decrease, threatening the rover's electronics and other temperature-sensitive systems when the heater is not running.
Nevertheless, according to Callas, a detailed analysis of the Rover systems shows that it should have survived its dust test. It's just about building enough charge to wake up, program errors, and make contact with Earth.
"I think everyone is now closer to their emails and their cell phones because we think now when we start to hear," Callas said.
The story of Opportunity is an unlikely story of exploration and scientific success of a spaceship that lasts only 90 days and survives, albeit with a variety of age-related illnesses. for more than 14 years since it hit an airbag-cushioned landing in January 2004.
Given the plethora of data already gathered during the extended mission, a failure to wake up while it disappointed its legions of fans would not be regarded as a failure in any traditional sense. Few space missions have a larger track record, and scientists are confident that the Rover will be able to continue its groundbreaking exploration.
Even if sunlight on Opportunity's solar fields should fall again, it could take a few weeks to make contact
"The problem is that electronics still have parasitic loads," Callas said. "It's like your TV at home – even if you've turned off your TV, it still draws power from the wall socket, and even if the rover is off, the electronics will still waste energy at a low level."
Make these parasitic loads about 40 watt-hours of energy. Another 220 watt hours could be wasted because of an external heater that got stuck early in Opportunity's mission.
Air traffic controllers have dealt with this problem by putting the rover into "deep sleep" every night to secure the heating was switched off. Opportunity woke up every morning thanks to its fully charged batteries.
"It's like having a light switch in your house, so go outside every night and turn off the main switch for your house," Callas said. "This is like a deep sleep on the rover, we turn off everything to stop the heater."
But if Opportunity initially lost enough energy to trigger a clock error, "the rover loses time and does not know when should sleep properly deep, "says Callas added. "And so maybe it's not asleep when this heater is glued on, and so it may be a waste of energy that we try to recharge the batteries."
A clock error probably developed in the wake of the extended energy failure. If so, Opportunity's computer resets the time each time it wakes up to a time in the future and then sets timers to initiate communication attempts.
"The rover does not wake up in the middle of the night waking up only during the day, but we will not know when during the day," said Callas. "It could be a Whack-a-Mole game, it could get up at a certain time of day, and then we could not hear for three days and then wake up at another time of the day."
To cover these scenarios, the Deep exists NASA's Space Network from Huge Antennas It's used to relay data and commands to spacecraft that spread across the solar system. It "listens" several times for opportunities reputation at different times of the day and covers a wider frequency range to be on the safe side.
Asked how confident he was about the opportunity's being woken up, Callas said the odds are better than 50 to 50.
"If we do not throw a whole bunch of dust on the arrays, if we have at least 50 Have percent clean arrays The vehicle should now be charged, "he said. "As long as the batteries have not broken, and we do not think they have, this thing should wake up.
" If we have not heard in a couple of months (of it) then yes I'm really worried. But I think in the next weeks, four or five weeks, we should hear something. "