Nasa’s Mars helicopter experienced an “in-flight anomaly” on its sixth flight from the Red Planet, tossing and turning in the foreign atmosphere as the space agency attempted to get it back under control.
The Ingenuity craft’s flight was intended to demonstrate aerial-imaging capabilities, climbing 10 meters before flying over the Martian ground capturing images.
It made its first flight in April 2021 – flying into the air, hovering for 30 seconds, and then touching down again safely. Following that success, Nasa said the helicopter would continue with scientific research rather than being abandoned.
For the first 150 meters of the helicopter’s latest flight, Ingenuity performed as expected; but as it reached its end, the helicopter began tilting back and forth in an “oscillating pattern”, Nasa says.
“This behaviour persisted throughout the rest of the flight. Prior to landing safely, onboard sensors indicated the rotorcraft encountered roll and pitch excursions of more than 20 degrees, large control inputs, and spikes in power consumption.”
Ingenuity keeps track of its motion using an onboard inertial measurement unit (IMU) which monitors the helicopter’s acceleration and rotational rate.
As this would not be stable on its own, the IMU also uses a navigation camera that takes 30 pictures a second of the Martian surface to feed into the navigation system – along with a timestamp of when the image was taken – so that an algorithm can correct its estimates of the helicopter’s position, velocity, and attitude.
The issues occurred 54 seconds into the flight, when a glitch was noticed in the pipeline of images being delivered to the navigation camera. This caused a single image to be lost and, more vitally, meant that later navigation images had inaccurate timestamps.
“From this point on, each time the navigation algorithm performed a correction based on a navigation image, it was operating on the basis of incorrect information about when the image was taken. The resulting inconsistencies significantly degraded the information used to fly the helicopter, leading to estimates being constantly ‘corrected’ to account for phantom errors,” Håvard Grip, Ingenuity’s Chief Pilot, said.
In spite of these difficulties, Ingenuity was able to maintain its flight and land safely on the surface of Mars.
“While the flight uncovered a timing vulnerability that will now have to be addressed, it also confirmed the robustness of the system in multiple ways,” Grip added.
“While we did not intentionally plan such a stressful flight, Nasa now has flight data probing the outer reaches of the helicopter’s performance envelope. That data will be carefully analysed in the time ahead, expanding our reservoir of knowledge about flying helicopters on Mars.”