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“One of the most fun ways to do engineering is to think of all the things that can go wrong,” says Olivia Billett.
Billett is a Lockheed Martin engineer who led a team that designed and operated the science mission for the OSIRIS-REx spacecraft. This week, the rover appeared to take a geological sample from an asteroid 220 million miles away that will return to earth, an astonishing technical achievement. And one of the reasons it did was that Billett and his colleagues were up for some deep space surprises.
Billett and Lockheed have experience with missions to Mars and other planets, but they faced new challenges exploring the asteroid Bennu. “When you’re in orbit around a planet, gravity is such a dominant force and everything else is noise,” explains Billett. “You know exactly where the spacecraft will be in relation to the planet weeks into the future.”
Bennu, although roughly the size of the Empire State Building, is much smaller than a planet and has a weaker gravitational pull. That means everything from solar radiation to the spacecraft’s internal motion can throw it off course. For planetary missions, the Billett team could take weeks to design and test a maneuver. For this effort, they have been downloading information from the spacecraft’s sensors, plotting maneuvers, testing them, and sending the instructions into space, overnight.
The OSIRIS-REx sample collector design is perhaps the most unique aspect of the spacecraft: an 11-foot-long arm that began life as a plastic cup and a canister of compressed air in an engineer’s garage. Called TAGSAM, for its touch-and-go sampling mechanism, it is briefly pressed on the surface of Bennu, which explodes with nitrogen gas, propelling dust and small rocks into prepared containers.
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The mission launched in 2016, and when it arrived at Bennu in 2018, scientists were in for a surprise: They had anticipated that Bennu’s surface would be like a sandy beach. Instead, it was pretty rocky. That meant the spacecraft couldn’t rely on laser rangefinders to guide it to the surface, as they couldn’t distinguish between a rock and a patch of sand. Instead, OSIRIS-REx would use onboard cameras and software that could analyze the surface to guide it towards landing. The next two years were spent examining Bennu and practicing for the finishing touch this week.
In the next few days, we’ll find out if OSIRIS-REx has gathered enough rocks and dust to begin its return journey, or if it needs to make one or two more attempts to collect a sample. If all went well, the spacecraft will parachute its cargo to New Mexico in 2024. Scientists, who came up with the idea for this mission more than eight years ago, are eagerly awaiting these materials because they could help explain how our system grew. solar. and it changed over time, potentially increasing our understanding of the origins of life on Earth.
This astronomical tag game has another reason: Bennu’s orbit will pass quite close to Earth in the next century, with a slim chance of a disastrous impact on our planet. The detailed understanding that NASA has gained of the asteroid will allow us to more accurately predict the asteroid’s trajectory and potentially allow us to take defensive action if Bennu re-marks Earth.
A version of this story originally appeared in the Quartz’s Space Business newsletter.
