Mission Update After Ingenuity’s Flight 15: Craters, Swashes, and Servo Wiggle
Ingenuity’s mission on Mars has been a resounding success, but it is not without its emergent challenges; reports have returned from the space copter’s latest exploits, and things are getting tough out there. This fall, we experienced solar conjunction with Mars, where the two planets line up on exactly opposite sides of the sun. It’s a cool astronomical event, but it also forces a communications blackout that takes weeks to clear up, because the Sun’s radio emissions can corrupt signals we try to send between here and there. Ingenuity has also been dealing with declining atmospheric pressure for some weeks, as the Martian seasons roll ahead. And now, as if it wasn’t tough enough piloting a space helicopter on Mars, a mystery wobble is forcing NASA to decide whether to patch Ingenuity’s flight software.
Just after flight 13, telemetry reported a mechanical wobble in the swash plate atop Ingenuity’s rotor shaft. Eventually, it was traced to a minute oscillation that appeared to come from two of the six flight control servos. Thanks to the infuriating nature of intermittent problems, it showed up once and then vanished, and so far the problem isn’t easily repeatable. Mission scientists have tested the helicopter with a series of “servo wiggles,” but have been unable to reproduce the same deviation.
After communication with Ingenuity was restored, the scientists fired up the space copter for flight 14, a 23-second test hop at 2700RPM. Again, no wobble. Never one to pass up a chance to do a little science, Ingenuity “opportunistically” snapped a bunch of images of scientific interest during that hop, including a burst of images taken at seven frames per second. The raw images are still being processed, but like the rest of the frames captured by Ingenuity on its flights, as soon as they’re posted they are available to the public via Ingenuity’s mission portal.
Then, the rotorcraft started the home stretch of its months-long excursion. After more than a dozen successful outbound flights, the helicopter turned and began to make its way toward home base with a two-minute flight, the first of perhaps half a dozen that Ingenuity will make before it reaches Perseverance. This most recent flight is Ingenuity’s second after the solar conjunction, and its fifteenth overall. NASA announced its success via Twitter, and while they haven’t put out official stats from the flight as of this writing, here are Ingenuity’s most current performance numbers:
These high-RPM test flights are critical because they allow mission control to test its models for flight in an extremely low-pressure environment. Mars’ northern hemisphere is in the middle of summer, which means that its already delicate surface pressure drops by a third, settling at a wispy one percent of the sea-level pressure here on Earth. With fewer air molecules to push around, Ingenuity has to spin its rotor up to higher and higher speeds in order to stay aloft. But these more demanding flights also generate data on “critical high-RPM motor performance, which the team will use to design and tailor upcoming low-density flights in the months ahead,” said Teddy Tzanetos, Ingenuity Team Lead at NASA’s JPL.
The space copter’s current mission is to rendezvous with Perseverance, scouting its path for a northward sortie along the eastern edge of the Seitah region. After rounding the curve of the Seitah depression, the pair will tack northeast past the Octavia E. Butler landing site. From there, they will skirt around the rim of another crater, before turning west again to head for Three Forks, an ancient river delta that opens up at the northwestern edge of Seitah.
The delta is thought to be full of sediment and rocks, laid down in primordial floods that carved out a riverbed and filled up Jezero with water and turned it into a crater lake, with a flat bottom covered in ripples of silt and sand. Perseverance has taken some spectroscopic readings that back up the hypothesis; like craters in Arabia Terra just to the east, Jezero’s sediment is loaded with clay, which forms in the presence of water. It confirms that Jezero held a lake. (Jezero actually means “lake” in many Slavic languages.) But our imaging resolution hasn’t been good enough to test these fine assumptions, so the only way to know for sure was to go there and check. “Confirming that there was a lake in Jezero Crater is the first major science result of the mission,” explained two Perseverance team members, Melissa Rice and Briony Horgan, in an essay. “In the coming year, Perseverance will drive up to the top of the delta, studying the rock layers in microscopic detail along the way and collecting many samples. When those samples eventually make their way to Earth, we will learn if they contain signs of microbial life that may once have thrived in this ancient lake on Mars.”