LOS ANGELES (AP) -- A design error in the positioning of gravity-switch devices likely caused the parachute system of NASA's Genesis mission to fail, allowing a capsule with samples of the sun to smash into the Utah desert last month.
The likely cause identified by a Mishap Investigation Board was announced Thursday by NASA.
The switches sense the braking caused by the craft's entry into Earth's atmosphere and then start a timing sequence that leads to deployment of a drogue parachute and then a parafoil, NASA said.
A specially equipped helicopter was supposed to snag the parafoil during the descent on Sept. 8 and then gently lower the capsule to the ground to prevent damage to panels that collected atoms and ions from the solar wind during nearly three years in space.
Instead it impacted the Utah range at nearly 200 mph, which NASA officials have termed "a hard landing." The solar collection wafers shattered into pieces that fill more than 3,000 containers, but scientists remain optimistic that the samples will be useful.
"This single cause has not yet been fully confirmed, nor has it been determined whether it is the only problem within the Genesis system," MIB chairman Michael G. Ryschkewitsch said in a statement.
"The board is working to confirm this proximate cause, to determine why this error happened, why it was not caught by the test program and an extensive set of in-process and after-the-fact reviews of the Genesis system," he said.
Genesis and its sample return capsule were built by Lockheed Martin Astronautics at its facility in Waterton, Colo., where the hardware was being examined by the MIB.
The mission was managed by NASA's Jet Propulsion Laboratory in Pasadena, Calif., where the craft's damaged lithium sulfur dioxide battery was being evaluated.
"Both Lockheed Martin and JPL have been providing every possible support to our investigation," said Ryschkewitsch.
The board expects to complete its work by late November, NASA said.
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