A software bug would explain the crash of Schiaparelli on Mars

schiaparelli-landingIf the launch of the ExoMars Orbiter around Mars can be considered a great success for Europe in space, the crash of the lander Schiaparelli on the surface of the red planet leaves a taste of incompleteness. An investigation was launched into the cause of the crash because the next mission ExoMars 2020 will see ESA send a robot on Mars. The first findings of the investigation show that an erroneous data would have pushed the landing sequence and rushed Schiaparelli to the ground.

Schiaparelli sent a lot of data before its crash

Nobody, apart from NASA, has failed so far to put a device in working condition on the planet Mars. Its mission is ExoMars, ESA was allied with Roscosmos, the Russian space agency but this has not prevented its Schiaparelli module crashing to the surface. Engineers are investigating the reasons for this failure on October 19 as the next mission ExoMars 2020 is already looming.

exomars2016-descent

The sequence of entry into the atmosphere and landing of Schiaparelli is abruptly interrupted when the IMU began to pass erroneous data.

Fortunately, during its descent Schiaparelli gave hundreds of megabytes of data, which allow to follow in detail the process of entry into the Martian atmosphere. It appeared that the initial stages of entry have been successful until the opening of the parachute. The lander then was at an altitude of 12,000 m 1730 km/h, in line with the originally computed sequence values. The descent continued normally until the ejection of heat shield at an altitude of 7,800 Mr. Doppler radar to measure the altitude of Schiaparelli, the next phase is to drop the CAP and the parachute as soon as the altitude of 1200 m is reached. Here is that another instrument will play the disorders festivals it’s the IMU for Inertial Measurement Unit. It delivers to the calculator a measure of rotation and angle of the lander, although data obviously important for the calculation of the actual altitude of the lander. It is this information that then dictates the start-up of the retro-rockets in the final stages of landing.

The Schiaparelli navigation software hurriedly dumped the parachute

schiaparelli-impact-on-mars

The impact of the lander on Mars spotted by NASA (Credit: NASA-JPL/Caltech/University of Arizona)

While the descent module rushes to the Martian soil, at the opening of the parachute the IMU starts sending erroneous data so well that for the navigation computer, the calculation of altitude becomes… negative! The computer then estimated that LG has happened on the ground, he commands then the headdress and the parachute drop. Schiaparelli is a particularly unwelcome because initiative instead of 1200 m, still 3,700 Mr. the retro-rockets are then briefly turned on then off and systems designed to be deployed once I get on the ground are activated. This scenario could be replayed in simulation, which suggests that it is this erroneous data of the IMU who pushed the navigation software to apply the procedure for landing too hastily. The investigation should continue until the beginning of the year 2017 for good identify the reasons for the crash and fix what needs to be for ExoMars 2020.
This bug is particularly heartbreaking at the time or code analysis tools to identify cost overruns of threshold of variables as can arrival with data from sensors. Many of the embedded software developers know the story of the crash of the first flight of Ariane 5. The European rocket was damaged in the waves of the Atlantic because its inertial guidance software, developed for previous models of Ariane, had not been able to manage the much more powerful acceleration of the new rocket, which resulted in an overrun of value in a variable of type integer and caused the loss of the rocket.

Translation : Bing Translator

Sources :

“ESA: Mars lander crash caused by 1-second inertial measurement error”, SpaceNews, November 23, 2016
“Schiaparelli landing investigation makes progress”, ESA release, November 23, 2016
“Exomars 2016 schiaparelli descent sequence”, ESA release, February 24, 2016

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