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WRITTEN HISTORY FOR CBS NEWS AND USED WITH PERMISSION
Flying controllers have not heard of NASA's rover Opportunity Mars since June 10, when an increasingly severe global dust storm prevented the sun from charging robot batteries. But the dust storm is coming down and the engineers hope that the long-term vehicle will wake up and call home in the coming weeks.
"The weather improves on Mars," said John Callas, NASA's Jet Propulsion Laboratory project manager.
This opacity, a measure of the effectiveness of suspended dust that blocks sunlight, reached record levels as the storm developed in June. A major dust storm in 2007 had a level of opacity, or tau, greater than 5.5 while the current storm had an estimated tau of nearly 11 to 6 June.
a range where energy should be generated by solar panels, "Callas said in an interview with CBS News. "So we're getting closer to the time the vehicle should start charging, we're looking at it every day, people are betting when they think we'll hear about it."
But this n & # It's not a safe thing.
Mars has now overtaken its closest point of approach to the sun in two and the dust storm, which has kept the atmosphere warmer than usual, is decreasing. As time goes on, temperatures in Opportunity will drop, threatening the electronics of the rover and other temperature-sensitive systems in the absence of power to run its heaters. he should have survived the test of dust. It is simply a matter of accumulating a sufficient charge to wake up, to review its programming of failures and to try to contact the Earth.
"I think everyone stays closer to their email and mobile phone now when we start hearing something," Callas said.
The story of Opportunity is an unlikely story of exploration and scientific success achieved by a spacecraft designed to last 90 days and survive despite some age-related problems. for more than 14 years, since bouncing on an airbag landing in January 2004.
Given the abundance of data already collected during his extended mission, the fact of not waking up, although disappointing for his legions of fans, would not be considered a failure at traditional meaning. Few space missions have been more successful, and scientists hope the rover will be able to continue its forward-looking exploration.
Even though sunlight is thought to be falling on Opportunity's solar panels, it may take several weeks to make contact.
"The problem is that there are still parasitic charges on the electronics," Callas said. "It's like your home TV." Even if your TV is turned off, it still pulls energy from the socket, so even if the mobile is off, the electronics are still wasting energy. low energy. "
These parasitic loads represent approximately 40 watt hours of power, and an additional 220 watt hours could be wasted due to an external heater blocking full time at the beginning of Opportunity's mission. 19659004] The flight controllers solved this problem by putting the vehicle in "deep sleep" each night was off.Requirements then rose every morning thanks to its fully charged batteries.
"It's as if you had a switch in your house, so every night you go out and turn off the main breaker in your house, "Callas said." It's a bit like a deep sleep on the rover. We turn off everything so that the radiator turns off. "
But if Opportunity initially lost enough power to trigger a clock fault," the rover will lose track of time and will not know when to sleep properly, "Callas added. may not be sleeping deeply when this heater is blocked, and it may waste energy as we try to charge the batteries. "
failure. If this is the case, the computer will Opportunity will reset its clocks at a later time, then set timers to trigger communication attempts.
"The mobile will not wake up in the middle of the night. only wakes up during the day, but we will not know when during the day, "Callas said. "It could be a part of whack-a-mole, he could wake up at one o'clock in the day, then we will not hear for three days and wake up at a different time of the day."
To cover these scenarios, NASA's Deep Space Network used to relay data and commands to spacecraft distributed throughout the solar system, "listens" to the call of opportunity multiple times each time low and at different times of the day, covering a wider range of frequencies to be on the safe side.
Asked about his confidence in the eventual awakening of Opportunity, Callas said the odds were better than 50-50.
"If we did not throw a whole lot of dust on the bays, if we have at least 50% vehicle should be in charge about now," he said. "As long as the batteries have not disappeared, and we do not think they exist, this thing should wake up.
" If we did not hear (of that) in a few months, yes, then I am really worried. But I think in the next few weeks, four or five weeks, we should hear something. "
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