After 18 months, NASA's Curiosity Mars rover's onboard laboratories are back online. Thanks to over a year's work by engineers at the space agency's Jet Propulsion Laboratory (JPL) in Pasadena, California, the unmanned explorer has been taught a new way to use its crippled drill so that it can resume taking soil samples and conveying them to its robotic labs for analysis.
One of the primary tasks assigned to Curiosity since its touchdown on the Red Planet in 2012 has been to carry out extensive drilling operations with its robotic arm. This is part of its mission to seek out sites where life could once or still may contain life. For the first four years, the nuclear-powered rover operated longer and better than expected, but in December 2016, a problem occurred.
The key technology for Curiosity's soil sampling is its robotic arm, specifically its robotic hand, which is a complex assembly of sensors, drilling apparatus, and a system for accepting, grading, and conveying soil and rock powder to the laboratories located inside the body of the rover.
For drilling into rock, the hand's drill is placed over the desired spot, where it rests on two metal pins. Between these pins, the drill is extended, bores into the rock, and then recesses back into the hand to place the sample into the Collection and Handling for In-Situ Martian Rock Analysis (CHIMRA) sorting and transporting system. But in 2016, the drill malfunctioned and wouldn't extend properly on command, so drilling operations had to be suspended.
Using a duplicate rover at JPL, engineers studied the problem and came up with an alternative drilling method called "feed extended drilling," which was used for the first time on May 20 of this year. In this technique, the drill is fully and permanently extended and locked in place beyond the pins. The drill is then placed over the sample site and pressed down by the robotic arm like a person would with a power drill. Meanwhile, a force sensor lets the rover's computer know how far the drill is digging and how difficult the job is.
The second phase of the new operation was tested on May 31. This is "feed extended sample transfer," where CHIMRA is bypassed and the drill is suspended over the inlet to the laboratory to allow the sample to trickle down for later delivery to the analysis section.
According to JPL, the technique is not as simple as it sounds because the much drier conditions on Mars and the thin Martian atmosphere causes the powdered rock to fall out of the drill differently than on Earth. As a result, the engineers had to use images sent back by Curiosity to estimate how to get the proper amount of sample, which is in the milligram range, into the laboratory so that it's enough to work with, but not enough to clog the mechanism.
So far, results have been promising and mission control has even ordered Curiosity to return to old sites that it visited while the drill was unserviceable.
"The science team was confident that the engineers would deliver – so confident that we drove back to a site that we missed drilling before," says Ashwin Vasavada of JPL, the mission's project scientist. "The gambit paid off, and we now have a key sample we might have never gotten. It's quite remarkable to have a moment like this, five years into the mission. It means we can resume studying Mount Sharp, which Curiosity is climbing, with our full range of scientific tools."
The video below demonstrates the new drilling technique.
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