Dust from Mars’ global storm is finally beginning to settle out of the atmosphere. As proof, I can report that I’m able to see the south polar cap and several surface features through my telescope. Other observers have reported similar views. But the fact that NASA’s Opportunity rover has yet to “wake up” and contact its handlers back home means we still have a ways to go before the Martian air clears.
NASA’s Opportunity rover has been silent since June 10, when choking dust cut off solar power for the nearly 15-year-old rover. Now that it appears more dust is falling out of the atmosphere than being blown back into it, mission control is hoping to hear from Opportunity soon. There’s reason to be optimistic. Studies before the storm showed the batteries to be in good health, and because dust storms tend to moderate temperatures, the rover should have stayed warm enough to survive its solar limbo.
Just as they do on Earth, dust storms on Mars block sunlight from reaching the surface. Scientists use the “tau” unit to measure how much sunlight is screened by dust. The higher the tau, the less sunlight. The last tau measured by Opportunity was 10.8 on June 10, the highest ever recorded by the rover. Compare that to an average tau of 0.5 for its location. At the time, NASA reported that the sky was as dark as midnight over the rover.
JPL engineers predict that Opportunity will need a tau of less than 2.0 before the solar-powered rover will be able to recharge its batteries. NASA’s Mars Reconnaissance Orbiter (MRO) has been watching for surface features to become visible as the skies clear to help scientists estimate the atmospheric transparency.
During the previous week (Aug. 7-14), the tau was measured at 2.1 — tantalizingly within range — before rising back up to 2.5. According to the latest rover update, it’s possible Opportunity has had a problem with its mission clock, the only instrument still operating. The clock is programmed to wake the computer so it can check power levels. If the rover’s computer determines that its batteries don’t have enough charge, it will again put itself back to sleep. The clock also tells the rover when to communicate; if it doesn’t know what time it is, it won’t know when to send a signal. As a backup, Opportunity can use environmental cues like an increase in sunlight to make an assumption about the time of day.
Several times a week, engineers use NASA’s Deep Space Network, which communicates between planetary probes and Earth, to attempt to talk with Opportunity. The antennas ping the rover during scheduled “wake-up” times, and then search for signals sent from Opportunity in response. In addition, JPL’s radio science group uses special equipment on the antennas to record any radio signal coming from Mars during the rover’s daylight hours, then searches the recordings for Opportunity’s “voice.”
Assuming they finally do hear back, the engineering team will want to know the state of the rover, take its temperature and ask for a history of its batteries and solar cells usage. If the clock lost track of time, the crew will reset it much like the way you or I would re-enter the time on the microwave clock after a power outage.
The rover will take photos of itself to see how much dust has caked onto sensitive parts and solar cells and check to see if dust is affecting mechanical operations. Even if engineers hear back from Opportunity, there’s a real possibility the rover won’t be the same. The batteries have been inactive for so long, their capacity or ability to be fully charged up again may be reduced. This would affect running Opportunity’s heaters during the bitter cold Martian winter when the batteries could quickly lose charge and “brown out.” As for dust, it’s has always been a problem for Mars rovers, but most of it falls away — or is blown off — over time.
While you and I continue to watch Mars from our yards back on Earth, NASA’s best are waiting for a sign. To keep their spirits up they’ve been sending the rover a “wake-up” song each day since August 4 in hopes of hearing back. Granted it’s quirky, but a sense of humor has helped many of us get through tense times.
Here’s the playlist through Aug. 15:
- Wake Me up Before You Go-Go — Wham!
- The Trooper — Iron Maiden
- Dust in the Wind — Kansas
- Here Comes the Sun — The Beatles
- Rocket Man — Elton John
- Everlong — Foo Fighters
- Times Like These — Foo Fighters
- Bohemian Rhapsody — Queen
- Space Oddity — David Bowie
- Life On Mars? — David Bowie
- Alive — P.O.D.
- Telephone Line — Electric Light Orchestra
- Don’t Look Back — Boston
- Keep Yourself Alive — Queen
- I Will Survive — Gloria Gaynor
- (We’re Gonna) Rock Around the Clock — Billy Haley & His Comets
- I Won’t Back Down — Tom Petty
- Gold Heart Locket — Sam Bush