Dead Mars Lander Thought It Had Safely Landed Before It Crashed
Four minutes and 41 seconds into its descent sequence, the European/Russian-built lander apparently got disoriented.
Concept art of Schiaparelli firing its retrorockets. Image: European Space Agency/Roscosmos/Rlevente
The ExoMars Schiaparelli lander may have suffered a software glitch that caused it to crash into the Martian surface at 186 miles per hour, according to European Space Agency (ESA) mission leads quoted Tuesday in Nature.
The lander's last messages back to Earth indicate that the error occurred four minutes and 41 seconds into its entry, descent, and landing (EDL) sequence on Wednesday, October 19. At this late point in the lander's six-minute-long EDL, its onboard computer system prematurely jettisoned the heat shield and parachutes, apparently because Schiaparelli thought it was much closer to the surface than it was in reality.
The module then fired its retrorockets, but only for three seconds, instead of the 30-second-long burn that had been planned to guide it down to a gentle landing. This truncated burn may also have been prompted by the lander's confusion over its altitude. Though it was about two-to-four kilometers (roughly one-to-three miles) above the surface when the rockets fired, it behaved as if it was only a few meters from the ground, switching off its engine early to initiate the landing.
This conclusion is further validated by the fact that, as it hurled towards the crashsite, Schiaparelli activated its onboard instruments, designed to take temperature, pressure, and electric field readings. To the ExoMars team, this suggests that the module thought that it had successfully stuck the landing and was getting ready to radio information about its surface surroundings back to its home world.
"My guess is that at that point we were still too high," said ExoMars project scientist Jorge Vago in Nature. "And the most likely scenario is that, from then, we just dropped to the surface."
Bear in mind that this initial diagnosis is not final, and more details will have to be confirmed and hashed out as the post-mortem evaluation proceeds. ESA leads also stress that the ExoMars Trace Gas Orbiter (TGO) completed its maneuver into Martian orbit without a hitch, and it is expected to operate there for at least six years, so the mission as a whole is far from a wash.
Even so, the landing failure is obviously disappointing, the latest in a string of thwarted Martian landings for ESA and Roscosmos, its Russian partner on ExoMars. Soft-landing on another world is extremely difficult, and so far, only NASA has been able to conduct surface operations from Mars's surface. The European and Russian spaceflight communities had hoped Schiaparelli would demonstrate that the Martian landscape was accessible to other nations and agencies. Not this time, sadly.
Going forward, the ExoMars team will focus on the rooting out exact causes of the crash to prevent the same problem from compromising the second-generation ExoMars 2020 spacecraft, which includes a rover, scheduled for liftoff in four years.
The launch date for the ExoMars rover has already had been kicked back once, from 2018 to 2020, so it would be a shame to see it delayed further. A flexible timeline may be inevitable, however, to ensure the problem is fully addressed and to secure adequate funding for the next stage of ExoMars from ESA member state ministers.
"It would have been much nicer to be able to go to the ministers with a mission where both elements had performed flawlessly," Vago admitted. "As it is, we have one part that works very well and one part that didn't work as we expected. The silver lining is that we think we have in hand the necessary information to fix the problem."
We at Motherboard have spilled a lot of online ink about the unique pathos that our robotic explorers can cultivate over their lives and deaths. The idea of plucky little Schiaparelli gearing up to message its creators that it had pulled off its landing while, in actual fact, it was about to smash into the surface, explode, and leave a 49-by-131 foot burnt hole as a gravesite, is an especially excruciating new chapter of that saga. Rest in pieces, Schiaparelli, and best of luck to the ExoMars rover in ending NASA's unchallenged spacecraft monopoly on Mars.
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