It has traversed craters, taken photos of regions that would be difficult to reach on the ground, and served as a surprisingly resilient scout, adapting to the changing Martian atmosphere and surviving its harsh dust storms and frigid nights.
Now engineers and scientists at NASA’s Jet Propulsion Laboratory are concerned their four-pound, solar-powered drone is nearing the end of its life on Mars.
Winter is coming on Mars. The dust billows, covering Ingenuity’s solar panels and preventing its six lithium-ion batteries from fully charging. This month, Ingenuity missed a scheduled communications session with Perseverance, the Mars rover it relies on to send data and receive commands from Earth, for the first time since it landed on Mars more than a year ago.
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Will a dust-covered Ingenuity survive a Martian winter when temperatures routinely drop below minus 100 degrees Fahrenheit? And if not, how will the world remember the tiny helicopter that took $80 million to develop and more than five years to design and build? Those closest to the project say that with Ingenuity’s time running out, it’s difficult to overstate its achievements.
“The helicopter far exceeded those initial expectations,” Lori Glaze, director of NASA’s Planetary Sciences Division, told The Washington Post.
Given Martian atmosphere, the scientists and engineers working on Ingenuity weren’t sure the experiment would even succeed. Thomas Zurbuchen, deputy administrator for NASA’s directorate of science missions, said at the time it was an endeavor that forced NASA to find the “right line between crazy and innovative.”
When the first flight was a success on April 19, 2021, NASA announced it as a Wright Brothers moment. As a tribute, Ingenuity had a postage-sized piece of fabric from the brothers’ plane, known as a flyer, attached to a cable under the solar panel.
Ingenuity flew to Mars tethered to the belly of the Perseverance rover, star of NASA’s recent Mars mission. In February 2021, after covering some 300 million miles in seven months, Perseverance made a dramatic landing under a parachute with a secret code that read: “Dare Mighty Things.”
The rover, which is the size of an off-road vehicle, landed in an area of Mars known as Jezero Crater that once held water and could provide clues to the planet’s history and whether life existed there. The rover collects rock and soil samples that NASA hopes will be returned to Earth on a future mission, and uses its seven instruments to conduct science experiments and test new technologies.
Ingenuity was something of an add-on, a technology demonstration that could prove useful for future missions and allow the space agency’s scientists to explore more of the Martian landscape than they could by land alone.
But flying an autonomous drone on Mars would be extremely difficult. The atmosphere there is just 1 percent as dense as Earth’s, so to generate lift, the helicopter’s four-foot-wide rotor blades would have to rotate incredibly fast — 2,500 revolutions per minute.
“We built it as an experiment,” Glaze said. “So it didn’t necessarily have the flight-qualified parts that we use on big missions like Perseverance.” Components of smartphones, for example, were even bought off the shelf, so “there was a chance that they might not perform as expected in the environment. And so there was a risk it wouldn’t work.”
As Ingenuity flew on, controllers on the ground began to realize that their small project could make a big difference. Ahead of its fifth flight, they wrote in a blog post that “our helicopter is even more robust than we had hoped. The electricity system, which we’ve fretted about for years, provides more than enough power to keep our heaters on at night and flying during the day. The standard components for our guidance and navigation systems are also developing excellently, as is our rotor system. You name it, and it goes well or better.
As the feat progressed, NASA scientists became increasingly intrigued by the idea that this helicopter could potentially become an integral part of the mission.
“What happened, and it’s really crucial, after Ingenuity performed so well on those first five flights, the Perseverance science team came to us and said, ‘You know what, we want this helicopter to keep operating to help us at to help our exploration and achieve our scientific goals,'” said Glaze.
So NASA decided to keep flying.
On its sixth flight, Ingenuity ran into trouble. The helicopter navigates using a camera that takes 30 frames per second of the terrain below, each with a time stamp. An algorithm predicts what the camera should have seen at that particular moment, based on images taken just before. Then it calculates the difference between the predicted location and the actual location of features of the ground to correct its position, speed and altitude.
But on this flight the timestamps were wrong. As a result, Ingenuity looked like it was being flown by a drunk driver who “adjusted its speed and pitched back and forth in an oscillating pattern,” NASA said on the blog.
Despite this, he was able to land safely within 16 feet of his target because “considerable effort was expended to ensure that the helicopter’s flight control system had adequate ‘stability margin’,” NASA wrote. In other words, “Ingenuity literally fought its way through the situation.”
Flight 9 in July was also a “nail biter”, as NASA wrote. Not only because Ingenuity broke records for flight duration and cruising speed, but because it flew over a crater, “an area called ‘Séítah’ that would be difficult to traverse with a ground vehicle like the Perseverance rover,” NASA wrote on its blog.
Because Ingenuity was designed as an experimental technology demonstration, engineers designed it to fly over largely flat terrain and be more easily navigated by its onboard camera. For this flight, however, Ingenuity would have to dive into the crater. That required it to reduce its speed and for engineers to tweak the navigation algorithm. The flight was a success, and Ingenuity was able to beam back color photos of the region, including a location that some believe “could record some of the deepest water environments in ancient Lake Jezero,” NASA wrote. “Given the tight mission schedule, they may not be able to rover visit these rocks, so Ingenuity may offer the only way to study these deposits in detail.”
Since then, Ingenuity has continued to work, overcoming obstacle after obstacle. Sometime in September, during its pre-flight check, it discovered an engine problem “and did exactly what it was supposed to do: it canceled the flight.”
About a month later the problem was resolved and the flight went back.
In April, it made another discovery – as it flew over the parachute slowing the rover for its Mars landing, it spotted the ruins of the shell that had protected the rover as it plummeted toward the Martian surface. There were a pair of man-made objects sitting on another planet, images that “just blew my mind,” Glaze said. In the past, NASA was able to detect vehicles on the surface of Mars from a spacecraft orbiting far away. But here were pieces of hardware, up close, at such high resolution that the “Dare Mighty Things” encoded into the shaft were visible through a thin layer of red Martian dust.
Then, 10 days later, on April 29, it made its last flight to date, #28, a quarter-mile jaunt that lasted two and a half minutes. Now NASA is wondering if this will be the last.
The space agency believes the helicopter’s inability to fully charge its batteries caused the helicopter to enter a low-power state. When it went to sleep, the helicopter’s onboard clock was reset, like household clocks do after a power outage. The next day, as the sun rose and began charging the batteries, the helicopter was out of sync with the rover: “When Ingenuity thought it was time to contact Perseverance, the rover’s base station was essentially not listening,” he said NASA wrote.
Then NASA did something extraordinary: Mission controllers ordered Perseverance to spend most of May 5 listening for the helicopter.
Finally, little Ingenuity called home.
The radio link, NASA said, “was stable,” the helicopter was healthy, and the battery was 41 percent charged.
But, as NASA warned, “One radio communications session doesn’t mean Ingenuity is over the hill.” The increased (light-reducing) dust in the air means that charging the helicopter’s batteries to a level that would allow vital components (like the clock and heaters) to stay powered throughout the night presents a significant challenge stay.”
Maybe Ingenuity will fly again. Maybe not.
“At this point, I can’t tell you what’s going to happen next,” Glaze said. “We’re still working on finding a way to fly it again. But persistence is the primary mission, so we need to start setting our expectations appropriately.”