ExoMars Lander Crashed Because It Thought It Was Underground

The first ExoMars spacecraft arrived in orbit of Mars last October as part of a join European-Russian mission to search for evidence of life on the red planet. However, the Schiaparelli lander encountered issues during its descent and was lost. Now, an analysis from the European Space Agency (ESA) details the failure and makes suggestions(Opens in a new window) as to how the second phase of the mission might avoid a similar fate.

The saucer-shaped Schiaparelli lander undocked from the ExoMars Trace Gas Orbiter and started its descent on October 19th of last year. The lander was non-mobile and had a non-rechargeable battery pack. So, it would have spent its entire four-day life in a single spot on Mars, returning data on wind speed, humidity, pressure, temperature, and more. However, the lander never sent back a signal that it landed successfully, and several days later NASA's Mars Reconnaissance Orbiter spotted the lander's crash site with its HiRISE camera.

Mission control did receive about 600MB of data from the Schiaparelli lander as it was falling through the atmosphere. That was enough to figure out what went wrong and (hopefully) prevent it from happening again. The report confirms early suspicions that the problem stemmed from the Inertial Measurement Unit (IMU) failing to properly respond to the unexpectedly high rate of rotation as the lander's parachute deployed. This kicked off a chain reaction that led to the crash.

The IMU was supposed to relay rotation information to Schiaparelli's guidance computer, but it became "saturated," when the rate of rotation exceeded its operational parameters. The lander stabilized itself, but the guidance computer was left with incorrect orientation information -- the lander thought it was upside-down. As a result, the guidance computer calculated that Schiaparelli was actually below ground level when it was actually still about 12,000 feet (3,700 meters) from the surface. Believing that it had already "landed," the craft jettisoned its parachute and fired its landing rockets for three seconds instead of the intended 30 seconds. It impacted Mars at 335 mph (540 kph).