http://gizmodo.com/a-crazy-miscalculation-doomed-the-sciaparelli-lander-1789319670
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.
revelation is painting a clearer picture of what happened during the failed
landing on October 19.
Schiaparelli deployed its parachute normally at an altitude of 7.5 miles (12 km)
heat shield was ejected when it reached an altitude of 4.85 miles (7.8 km). But
things went to complete shit from there.
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
a negative altitude. In other words, it thought the lander was below ground
level. Ouch.
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
kind of mechanical problem, that would be bad news. The ESA is planning a
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.
http://exploration.esa.int/mars/58590-schiaparelli-landing-investigation-makes-progress/
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