Schiaparelliā€™s heat-scorched shield. (Credit: ESA/ATG Medialab)

The European Space Agency has released new information about the crash of the ExoMars Schiaparelli lander. Soon after the deployment of its parachute, the lander made a miscalculation so bad that it thought it was below the Martian surface, when in reality was still two miles high.

The ESAā€™s investigation into the crash is far from over, but this latest revelation is painting a clearer picture of what happened during the failed landing on October 19.

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Schiaparelli deployed its parachute normally at an altitude of 7.5 miles (12 km) and at a speed of 1,075 miles per hour (1,730 km/h). As planned, the vehicleā€™s heat shield was ejected when it reached an altitude of 4.85 miles (7.8 km). But things went to complete shit from there.

As it was making its slow descent, Schiaparelliā€™s Inertial Measurement Unit (IMU) went about its business of calculating the landerā€™s rotation rate. For some reason, the IMU calculated a saturation-maximum period that persisted for one second longer than what would normally be expected at this stage. When the IMU sent this bogus information to the craftā€™s navigation system, it calculated a negative altitude. In other words, it thought the lander was below ground level. Ouch.

High-resolution images of the crash site. (Image: Copyright NASA/JPL-Caltech/University of Arizona)

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That fateful miscalculation set off a cascade of despair, triggering the premature release of the parachute and the backshell, a brief firing of the braking thrusters, and activation of the on-ground systems as if Schiaparelli had already reached the surface. This all happened while the vehicle was still two miles (3.7 km) above ground, causing a catastrophic free fall that sent the lander plummeting downward at 185 mph (300 km/h).

Encouragingly, this behavior was replicated in computer simulations, which means mission planners stand a good chance of correcting the anomaly. The exact cause of the IMUā€™s miscalculation was not disclosed, but if it was tripped by some kind of mechanical problem, that would be bad news. The ESA is planning a similar mission in 2020, which doesnā€™t leave much time for an engineering overhaul. A software glitch, on the other hand, would likely prove to be an easier fix. A full report of the investigation is expected in early 2017.

[ESA]

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