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NASA Sets a Grim Deadline for Saving a Beloved Mars Rover
Some mission employees are stunned.
31 Aug 2018
https://www.theatlantic.com/science/archive/2018/08/opportunity-mars-rover-nasa/569071/
Excerpts:
On Thursday, NASA announced it had set a deadline for the current recovery attempts for the rover. According to atmospheric data from a NASA orbiter around Mars, there will soon be enough sunlight reaching the surface for Opportunity to recharge its batteries and kick off some automated procedures to bring it back online—if it survived the storm in the first place. When that happens, the countdown begins.
“If we do not hear back after 45 days, the team will be forced to conclude that the sun-blocking dust and the Martian cold have conspired to cause some type of fault from which the rover will more than likely not recover,” said John Callas, the Opportunity project manager, in a press release. “At that point, our active phase of reaching out to Opportunity will be at an end.”
JPL said engineers will undertake “passive-listening efforts” for several months beyond that. Instead of sending commands to the rover, the Deep Space Network will listen to the frequencies transmitted by all the spacecraft on and around Mars, and engineers will check the recordings for Opportunity’s specific frequency. There’s a chance that Opportunity’s solar arrays may be caked in dust, which would prevent the rover from powering its batteries, regardless of the amount of sunlight present. But “the chances are small that dust accumulation would be the root cause of Opportunity’s lack of communication,” JPL said Thursday.
The decision has prompted an outcry from some current and former members of the Opportunity team who don’t agree with NASA’s recovery plan. They point out that NASA tried harder with Spirit, which landed on Mars with Opportunity in 2004. When the rover went silent in 2010 during extreme winter conditions, engineers spent 10 months actively listening for its calls, and then another five on passive efforts. Spirit never woke up.
NASA officials came to this conclusion based on their understanding of how opaque the Martian atmosphere is, a measure known as tau. The greater that value, the less sunlight permeates the atmosphere to reach the surface. Before it went silent, Opportunity’s instruments recorded a tau of a 10.8—far greater than the usual tau in the southern hemisphere, which oscillates between 1 and 2. (During the last big dust storm on Mars, in 2007, the tau barely topped 6.)
Without Opportunity, NASA has relied on an instrument on the Mars Reconnaissance Orbiter to provide measurements of the tau. They’re less precise, but they provide good estimates. According to the orbiter’s latest measurements, tau is now at 1.7. JPL officials believe that when that level dips to 1.5, there should be enough sunlight peeking through the atmosphere to let Opportunity charge. That’s when they’ll start the [45 day active recovery effort] clock.
Former and current Opportunity team members and others say the 45-day period is not long enough to account for the potential of atmospheric phenomena known as dust-cleaning events. In the past, dust devils have swept away grains on Opportunity’s solar arrays. Sometimes, the wind was so effective that the panels were restored to their original sheen.
Engineers have carried out simulations predicting Opportunity’s current conditions. But they can’t account for how much dust remains—if any—on Opportunity’s solar panels. “The initial results [of the simulations] suggest that if tau was below about 1.5, there is a chance, depending on the dust loading on the panels, that we would be able to hear from Opportunity,” says Matt Golombek, the project scientist for the Mars Exploration Rover mission, which covers Opportunity and the now-defunct Spirit. “Although we have an estimate of the dust in the atmosphere, we have no idea how much dust is on the panels.”
The tau on Mars should reach 1.5 within weeks, Lemmon says. Even if engineers detect a ping from Opportunity, it may take weeks before they hear another one. Because the rover has been without power for so long, the onboard clock may have failed. When it wakes, Opportunity won’t know what time it is, which means it won’t know when it should attempt to communicate with Earth. It’s possible the rover will attempt to call home when the Deep Space Network is not listening. “It may take weeks or even longer to actually get control of the spacecraft again,” Golombek says.
If engineers are able to regain steady communication with Opportunity, they will ask the rover to send information about its vitals. They’ll even ask the rover to use its camera to take selfies, so that engineers can see how its exterior fared in the storm. NASA says that after engineers assess the rover’s health, they’ll take a poll to determine whether they should attempt a full recovery.
Some mission employees are stunned.
31 Aug 2018
https://www.theatlantic.com/science/archive/2018/08/opportunity-mars-rover-nasa/569071/
Excerpts:
On Thursday, NASA announced it had set a deadline for the current recovery attempts for the rover. According to atmospheric data from a NASA orbiter around Mars, there will soon be enough sunlight reaching the surface for Opportunity to recharge its batteries and kick off some automated procedures to bring it back online—if it survived the storm in the first place. When that happens, the countdown begins.
“If we do not hear back after 45 days, the team will be forced to conclude that the sun-blocking dust and the Martian cold have conspired to cause some type of fault from which the rover will more than likely not recover,” said John Callas, the Opportunity project manager, in a press release. “At that point, our active phase of reaching out to Opportunity will be at an end.”
JPL said engineers will undertake “passive-listening efforts” for several months beyond that. Instead of sending commands to the rover, the Deep Space Network will listen to the frequencies transmitted by all the spacecraft on and around Mars, and engineers will check the recordings for Opportunity’s specific frequency. There’s a chance that Opportunity’s solar arrays may be caked in dust, which would prevent the rover from powering its batteries, regardless of the amount of sunlight present. But “the chances are small that dust accumulation would be the root cause of Opportunity’s lack of communication,” JPL said Thursday.
The decision has prompted an outcry from some current and former members of the Opportunity team who don’t agree with NASA’s recovery plan. They point out that NASA tried harder with Spirit, which landed on Mars with Opportunity in 2004. When the rover went silent in 2010 during extreme winter conditions, engineers spent 10 months actively listening for its calls, and then another five on passive efforts. Spirit never woke up.
NASA officials came to this conclusion based on their understanding of how opaque the Martian atmosphere is, a measure known as tau. The greater that value, the less sunlight permeates the atmosphere to reach the surface. Before it went silent, Opportunity’s instruments recorded a tau of a 10.8—far greater than the usual tau in the southern hemisphere, which oscillates between 1 and 2. (During the last big dust storm on Mars, in 2007, the tau barely topped 6.)
Without Opportunity, NASA has relied on an instrument on the Mars Reconnaissance Orbiter to provide measurements of the tau. They’re less precise, but they provide good estimates. According to the orbiter’s latest measurements, tau is now at 1.7. JPL officials believe that when that level dips to 1.5, there should be enough sunlight peeking through the atmosphere to let Opportunity charge. That’s when they’ll start the [45 day active recovery effort] clock.
Former and current Opportunity team members and others say the 45-day period is not long enough to account for the potential of atmospheric phenomena known as dust-cleaning events. In the past, dust devils have swept away grains on Opportunity’s solar arrays. Sometimes, the wind was so effective that the panels were restored to their original sheen.
Engineers have carried out simulations predicting Opportunity’s current conditions. But they can’t account for how much dust remains—if any—on Opportunity’s solar panels. “The initial results [of the simulations] suggest that if tau was below about 1.5, there is a chance, depending on the dust loading on the panels, that we would be able to hear from Opportunity,” says Matt Golombek, the project scientist for the Mars Exploration Rover mission, which covers Opportunity and the now-defunct Spirit. “Although we have an estimate of the dust in the atmosphere, we have no idea how much dust is on the panels.”
The tau on Mars should reach 1.5 within weeks, Lemmon says. Even if engineers detect a ping from Opportunity, it may take weeks before they hear another one. Because the rover has been without power for so long, the onboard clock may have failed. When it wakes, Opportunity won’t know what time it is, which means it won’t know when it should attempt to communicate with Earth. It’s possible the rover will attempt to call home when the Deep Space Network is not listening. “It may take weeks or even longer to actually get control of the spacecraft again,” Golombek says.
If engineers are able to regain steady communication with Opportunity, they will ask the rover to send information about its vitals. They’ll even ask the rover to use its camera to take selfies, so that engineers can see how its exterior fared in the storm. NASA says that after engineers assess the rover’s health, they’ll take a poll to determine whether they should attempt a full recovery.
