By akademiotoelektronik, 17/09/2022

Ingenuity: why the loss of a single photo disturbed the 6th flight of the helicopter on Mars

For its sixth flight, the ingenuity helicopter has experienced some disturbances.The reason ?Of a photo problem, fortunately without gravity.

Once is not customary, the trial campaign of the ingenuity helicopter met on May 22 an incident, fortunately without gravity, which disturbed the quality of its air program above the Martian soil-this takeoff wasThe sixth operated by the nasa giravion.New altitude, speed and trajectory objectives had been set for the occasion.

Five days after the anomaly detected in flight, the American space agency returns to the subject in a summary article published on May 27.We learn that if the first stage of the mission went well (namely to rise 10 meters from the ground then move 150 meters), all the rest of the program was disrupted by a strange behavior of the helicopter.

Indeed, Ingenuity began to oscillate in flight, bowing from front to back."Before landing safely," explains Håvard Gip, the main pilot of the Jet Propulsion Laboratory machine, the embedded sensors indicated that the Giravion had undergone rolled and pitch movements of more than 20 degrees, entriesimportant controls and energy consumption peaks.»»

Pour aller plus loin Écoutez le tout premier son de l’hélicoptère Ingenuity volant sur Mars

You miss an image and everything is offbeat

Today, NASA knows why these unforeseen maneuvers were caused: it is because of the loss of a single image photographed by Ingenuity during its flight.After 54 seconds of flight, details Håvard Grip, a bug in the images processing chain provided by the navigation camera led to the loss of a snapshot and caused a gap in the horoding of the following photos.

"Consequently, each time the navigation algorithm made a correction on the basis of a navigation image, it operated on the incorrect database at the time it had been taken. Les incohérences en résultant dégradaient énormément les informations utilisées pour piloter l’hélicoptère, conduisant à des estimations constamment corrigées»», relève-t-il.

First black and white image of the third Ingenuity flight on Mars.

Source : NASA/JPL-Caltech (photo recadrée)

The helicopter uses an inertial unit of embedded to follow the way it moves. Mais le système de navigation se sert par ailleurs d’une caméra pour confirmer et corriger les opérations de l’unité de mesure inertielle — elle seule ne peut en effet pas suffire, car « les erreurs s’accumuleraient rapidement, et l’hélicoptère finirait par s’égarer»».The camera is therefore used to crop the flight.

However, the images of the camera are horoded to know when they have been taken and to help the algorithm to determine if the trajectory corresponds to what is expected - through the analysis of the field, which takes up accounts of the previous photos.This is how the helicopter can correct its position, speed and attitude estimates.But the image flow must still be stable.

The good news is that this failure did not endanger Ingenuity.The machine was able to land very close to the landing site which was planned - to the nearest five meters.One of the reasons is due to the fact that NASA had the good idea to provide margins to include any errors without making an impossible or unpredictable flight.Thanks to this tolerance to errors, the bug of horodatages has been overcome.

Pour aller plus loin Que va-t-il arriver à l’hélicoptère martien Ingenuity à la fin de sa mission ?

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