Ingenuity gets the wobbles on sixth flight

Rotorcraft weathers navigation malfunction to land safely

Analysis of the first flight of Ingenuity’s extended mission on Mars, which took place on 22 May, shows the flight nearly ended in disaster, as the rotorcraft began wobbling one minute into its journey.

A photograph taken by Ingenuity during its sixth flight, 22 May 2021. Image credit: NASA/JPL-Caltech

The problem was traced to Ingenuity’s navigation system, which relies on speedy processing of photographs taken by the onboard camera. Each photograph is compared to the one before it, allowing Ingenuity’s flight software to determine the craft’s location with respect to the surface.

Fifty-four seconds into the sixth flight, the software failed to register one of the photographs. The loss was not in itself very significant, but it caused all pictures taken subsequently to be tagged with inaccurate timestamps. The navigation software relies on estimates of Ingenuity’s motion based on its recording of the craft’s rotor speed, tilt, and other mechanically measurable outputs, but because it then checks those calculations against the movement it actually records through its camera, the incorrect timestamps on the images meant the two data sets were no longer in agreement with one another.

The resulting cascade of anomalies literally threw the craft for a loop, causing excursions from vertical of as much as 20 degrees, and forcing the onboard systems to draw far more electricity from the batteries than usual in a series of worrisome power spikes. The craft eventually landed safely after a flight of approximately 215 metres. In spite of the problems experienced, Ingenuity managed to land less than five metres from its intended target. The flight reached an altitude of 10 metres above the Martian surface, a new record.

In a blogpost written by Håvard Grip, Ingenuity Mars Helicopter Chief Pilot at NASA's Jet Propulsion Laboratory, the craft robust programming was described as having come to the rescue: anticipating a scenario where timing errors might occur, the software designers ensured the craft would ignore all images during descent to the ground, making for a smooth landing to an otherwise wild flight.

Analysis of the anomaly is continuing.