Like every solar-panel-powered vehicle on Mars, maintaining electrical power always becomes an issue at some point in the mission. Last week, mission controllers at the Jet Propulsion Laboratory lost contact with the Ingenuity Mars Helicopter. While they were able to re-establish communications, which is done through the Perseverance rover, engineers know that keeping Ingenuity’s batteries charged is going to be increasingly difficult as the dark winter is on the way to Jezero Crater.
The engineering team had to do some trouble-shooting to figure out the issue, but they reported that the communications dropout on May 3, Sol 427 of the Perseverance rover’s mission at Mars, “was a result of the solar-powered helicopter entering a low-power state, potentially due to the seasonal increase in the amount of dust in the Martian atmosphere and lower temperatures as winter approaches.”
The amount of dust on the solar panels diminishes the amount of sunlight hitting the solar array, reducing Ingenuity’s ability to recharge its six lithium-ion batteries. When the battery pack’s state of charge dropped below a lower limit, the helicopter’s field-programmable gate array (FPGA) – basically the operating computer — was powered down.
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Even though Ingenuity flies through the air – and one would anticipate the dust would fly off the helicopter — dust on Mars is different from dust on Earth. Martian dust is electrostatically charged, so it clings to the solar panel’s glass. While many have said every solar powered vehicle on Mars should have a little whisk broom on its robotic arm or something like wiper blades to brush off the dust, engineers have said that would be difficult. The dust is also very gritty, and by trying to wipe it off, the solar panels could get scratched, damaging the panels and making the power problem even worse.
“We have always known that Martian winter and dust storm season would present new challenges for Ingenuity, specifically colder sols, an increase in atmospheric dust, and more frequent dust storms,” said Ingenuity Team Lead Teddy Tzanetos, in a press release. “Every flight and every mile of distance flown beyond our original 30-sol mission has pushed the spacecraft to its limits each and every sol on Mars.”
Ingenuity – the little 1.8 kg (4 pound) helicopter that has flown her way into our spacey hearts — became the first powered aircraft to operate on another world, making its first flight on April 19, 2021. The original mission plan was to make five experimental test flights over a span of 30 Martian days (sols). But Ingenuity has flown 28 times, covering 6.9 kilometers (4.2 miles).
With less sunlight, the batteries did not charge sufficiently and the FPGA lost power during the cold of night. The FPGA manages Ingenuity’s operational state, switching the other avionics elements on and off as needed to maximize power conservation. It also operates the heaters that enable the helicopter to survive frigid Martian nights, maintains precise spacecraft time, and controls when the helicopter is scheduled to wake up for communications sessions with Perseverance.
Ingenuity’s heaters are key to keeping electronics and other components within operational temperatures. As the FPGA turned off, its internal clock reset. JPL said that when the Sun rose the next morning and the solar array began to charge the batteries, the helicopter’s clock was no longer in sync with the clock aboard the rover. Essentially, when Ingenuity thought it was time to contact Perseverance, the rover’s base station wasn’t listening.
As Eric Berger from Ars Technica points out, while Ingenuity was initially viewed as an add-on demonstration mission, it has grown into much than that, and has become a scout for Perseverance, checking out the path ahead.
But when the team lost contact with the helicopter, the decision was made to halt all of Perseverance’s ongoing science activities for a full day to just sit there and listen intently for Ingenuity’s call. Former rover driver Scott Maxwell tweeted out how endearing and heartfelt that feels:
And now, with ‘ingenuity’ of the helicopter and rover teams, they have come up with a plan to keep Ingenuity warm and operating.
They will try to help the helicopter’s battery accumulate enough of a charge during the next few sols so that it could support all necessary spacecraft systems during the cold Martian night. They uplinked new commands to Ingenuity which lowers the point at which the helicopter energizes its heaters from when the battery falls below 5 degrees Fahrenheit (minus 15 degrees Celsius) to minus 40 degrees Fahrenheit (minus 40 degrees Celsius). The helicopter then shuts down quickly, rather than consuming the battery charge with the heaters. The team hopes this strategy will allow the battery to retain whatever charge it collected during the day. The Ingenuity engineers hope that after several days of the helicopter’s array soaking in the limited sunlight, the battery will have reached a point where the spacecraft can return to normal operations.
But there are some unknowns if this will work. Ingenuity has several off-the-shelf parts that weren’t designed for the cold of Martian winter.
“Our top priority is to maintain communications with Ingenuity in the next few sols, but even then, we know that there will be significant challenges ahead,” said Tzanetos. “I could not be prouder of our team’s performance over the last year, let alone our aircraft’s incredible achievements on Mars. We are hopeful that we can accumulate battery charge in order to return to nominal operations and continue our mission into the weeks ahead.”