ESA: Mars lander crash caused by 1-second inertial measurement error

[gary]

In an article today at SpaceNews.com, Peter B. de Selding reports that -

Originally Posted by Peter B. de Selding, SpaceNews.com

PARIS — The European Space Agency on Nov. 23 said its Schiaparelli lander’s crash landing on Mars on Oct. 19 followed an unexplained saturation of its inertial measurement unit, which delivered bad data to the lander’s computer and forced a premature release of its parachute.

Polluted by the IMU data, the lander’s computer apparently thought it had either already landed or was just about to land. The parachute system was released, the braking thrusters were fired only briefly and the on-ground systems were activated.

Instead of being on the ground, Schiaparelli was still 3.7 kilometers above the Mars surface. It crashed, but not before delivering what ESA officials say is a wealth of data on entry into the Mars atmosphere, the functioning and release of the heat shield and the deployment of the parachute — all of which went according to plan.

Article here -
http://spacenews.com/esa-mars-lander....MqNwH2sq.dpuf

[pluto (Hugh)]

Thanks for posting Gary.

[julianh72 (Julian)]

I'm sure there are good reasons why they programmed the lander such that a single instrument feed was used to trigger the parachute release and thruster firing, so that when that single data feed became saturated, the landing sequence was triggered prematurely. However, it does seem to be a contravention of long-standing design practice in the aerospace industry that you use multiple redundant feeds / processors, with independently designed systems and sensors for critical functions, and in the event of a discrepancy, you use a 2:1 voting majority to decide what to do next. (E.g. if one sensor says "We've landed!", but the other two say "No we haven't!", you conclude that you probably haven't yet reached the ground.) It's not exactly rocket science. (Well, actually, in this case it IS rocket science!)

As ESA Says - the main objectives of the lander project were to acquire understanding for future lander projects - one of those learnings should be to not forget the learnings of the past!