NASA’s Opportunity rover goes silent as massive dust storm engulfs Mars
NASA’s long-lived Opportunity rover is currently weathering a massive dust storm—the largest the solar-powered rover has had to endure in its nearly 15 years of surface operations. The vehicle has been operating in Meridiani Planum since January 2004.
The dust storm was first detected by NASA’s Mars Reconnaissance Orbiter on May 30, 2018, according to NASA, and is now covering more than a quarter of the planet—some 14-million square miles (35-million square kilometers)—and is expected to go global within days. Engineer’s at the space agency’s Jet Propulsion Laboratory (JPL) were unable to contact Opportunity on June 12, 2018, prompting controllers to assume the golf cart-sized rover is now in a low power fault mode.
“There’s a severe dust storm on Mars that’s threatening Opportunity. As a result the rover has fallen asleep and is waiting out the storm,” said John Callas, Opportunity’s project manager, during a media teleconference about the dust storm. “The project team is very concerned. We’re watching the weather and we’re listening with the Deep Space Network for signals.”
A low power fault mode means the charge in Opportunity’s batteries has dipped below 24 volts. At that threshold, the rover is designed to turn off all subsystems except for the mission clock—including the vehicles electronics heaters.
Periodically, the mission clock will wake the computer up to check power levels. According to NASA, if its batteries don’t have enough charge, it will go back to sleep. This cycle will continue until it has enough charge, or the vehicle succumbs to the cold Martian environment.
However, mission managers believe the rover’s internal temperature won’t drop below its design limit of minus 67 degrees Fahrenheit (minus 55 degrees Celsius). With the heat retained by the storm and the warming summer temperatures, the vehicle is expected to maintain a steady temperature of about minus 33 degrees Fahrenheit (minus 36 degrees Celsius).
NASA said that because of the intense dust storm, mission engineers believe it is unlikely the rover will have enough sunlight to communicate at its current location in Perseverance Valley for at least the next several days.
After the MRO team noticed the storm growing near Opportunity’s location, they contacted the mission team on June 1. The rover’s power level was at 645 watt hours per day at that time with a opacity level, called tau, of around 0.3. The next day, the tau level was at 1.3 and by June 4, the opacity was at 2 with the solar panels generating 345 watt hours.
On June 5, the rover team implemented a low power plan, which meant that all science operations were halted and it placed into a sleep mode for two days with no communications. At that time, power levels were at 133 watt hours.
Then on June 8, the team chose to do another low power plan and didn’t communicate with the rover until June 10. During that transmission, Opportunity sent back data showing the storm was officially worse than the one it weathered in 2007. That storm had a opacity level of around 5.5, according to NASA. This storm is now at least 10.8 with its solar panels producing only 22 watt hours—barely enough for the mission clock to run.
The rover has not been heard from since.
In a Twitter tweet thread on June 11, Bobak Ferdowsi—an engineer at JPL who gained media attention in 2012 during the landing of the Curiosity Mars rover because of his mohawk hairstyle—said the 2007 storm took energy from the rover’s 700 watt-hours per day-generating solar panels to nearly 100 watt hours per day. He added that would be equivalent to a 100 watt light bulb operating for one hour.
“The good news is the dust storm acts like a nice insulating layer, keeping the rover relatively warm at night, when she’d usually be spending energy on heaters, so there’s hope,” Ferdowsi said.
If the rover’s power production gets much lower, it could go into what’s called a mission clock fault, which means that Opportunity won’t know what time it is. In the event that happens, it will attempt to wake every four hours or so (assuming it has enough power to do so) to see if the sun is up. If it isn’t, it will set another hour-hour alarm and try again until it is daytime to try to communicate with an orbiter.
The June 10 transmission also showed the rover’s temperature was about minus 20 degrees Fahrenheit (minus 29 degrees Celsius), NASA said. Because the temperature isn’t expected to get much lower, it is expect that Opportunity can sit in this configuration for an extended period of time until the storm blows over.
“As soon as the skies clear, we’ll have ample energy production,” Callus said.
Ultimately, it was the cold that caused Opportunity’s sibling rover Spirit, which operated on the opposite side of Mars in Gusev Crater, to cease functioning in 2010. The circumstances, however, were different.
A stalled wheel on Spirit caused the vehicle to get stuck in a sand trap in an area called Troy. As winter approached, the spacecraft, which was farther from the equator (15.5 degrees south) than Opportunity, was unable to move to a slope to position its solar panels toward the lower-horizon sun.
Ultimately, lower sunlight levels likely caused Spirit to enter into a low power fault mode. The last communication with the rover was March 22, 2010. JPL continued to try to communicate with the vehicle until May 25, 2011, without success.
It was speculated that excessively cold internal temperatures prevented Spirit’s survival heaters to run. Cold temperatures can cause damage to critical components and connections, which is likely what prevented the rover from operating.
Meanwhile, NASA’s other active rover, Curiosity, is also experiencing this dust storm from its location halfway around the planet in Gale Crater. However, that rover is powered by a radioisotope thermoelectric generator—a device that uses heat from decaying plutonium to create power—rather than solar panels. As such, dust is much less of a concern for the mission controllers operating it.
As for the team at JPL operating Opportunity, Callas said they have a very strong bond with the rover and often anthropomorphize it.
“The analogy I would use right now is it’s like you have a loved one in a coma in a hospital,” Callas said. “The doctors are telling you that ‘OK, you’ve just got to give it time and she’ll wake up. All the vital signs are good, so it’s just waiting it out.’ But if it’s your 97-year-old grandmother, you’re going to be very concerned.”
Derek Richardson has a degree in mass media, with an emphasis in contemporary journalism, from Washburn University in Topeka, Kansas. While at Washburn, he was the managing editor of the student run newspaper, the Washburn Review. He also has a website about human spaceflight called Orbital Velocity. You can find him on twitter @TheSpaceWriter.