Ten months after guiding NASA’s DART spacecraft toward a small asteroid, the probe hit a bull’s-eye today on a planetary defense training tour that got help from engineers at Aerojet Rocketdyne in Redmond, Washington.
DART – the acronym for Double Asteroid Redirection Test – was designed to see how a projectile would have diverted a potentially threatening asteroid away from Earth.
In this case, the object did not pose any actual threat. DART’s target was Dimorphos, an asteroid the size of the Great Pyramid of Egypt that orbits a half-mile-wide asteroid called Didymos. Both celestial bodies travel on a path that extends beyond the orbit of Mars and gets close enough to Earth’s orbit for study. At the time of today’s collision, the double asteroid system was about 7 million miles from our planet.
The mission team clapped and cheered at the Johns Hopkins University Applied Physics Laboratory in Maryland as near-realistic images from the spacecraft’s DRACO camera showed Demorphos looming even further in the metaphorical windshield. The body of the DART spacecraft, which NASA says weighed about 1,260 pounds and was roughly the size of a vending machine, collided with the small moon at an estimated speed of 14,000 miles per hour.
“Oh, awesome!” The camera has stopped working, said Laurie Glaese, director of the Planetary Science Division in NASA’s Science Mission Directorate. “Now when the science begins.”
After the collision, APL director Ralph Simmel joked about the destruction of the spacecraft. “I’ve never been so excited before to see a signal go away,” he said.
A backpack probe called LICIACube observed the collision from a safe distance and is due to send out its own images over the next few days. Over the next two months, observations by ground-based telescopes as well as NASA’s Hubble Space Telescope and James Webb Space Telescope will trace how Demorphos’ orbit around Didymus was altered by the crash.
The effect is not expected to be dramatic – perhaps a difference of several minutes in the 11.9-hour orbital period of Dimorphos. Caroline Ernst, a DRACO instrument scientist at APL, said the young moon looked like a loosely connected pile of rubble rather than a solid piece of rock. This can affect the amount of the DART effect that translates into an orbit shift.
However, data collected from the DART mission – as well as lessons learned from previous missions (such as NASA’s Deep Impact, which included the crash of a comet in 2005) and from future missions (such as the European Space Agency’s Hera, which are due to be examined once Others with Didymos and Dimorphos in 2026) — could help scientists figure out how best to divert deadly asteroids like the ones that wiped out the dinosaurs 66 million years ago.
“At its core, DART represents an unprecedented success for planetary defense, but it is also a unit mission of real benefit to all of humanity,” NASA Administrator Bill Nelson said in a press release. “While NASA studies the universe and our home planet, we are also working to protect this home, and this international collaboration has turned science fiction into science fact, demonstrating one way to protect Earth.”
The Aerojet Rocketdyne team in Redmond shared the success by playing a role in building two propulsion systems for the DART spacecraft.
Twelve Aerojet MR-103G Hydrazine thrusters performed a number of course correction maneuvers during the spacecraft’s 10-month flight to Didymus. Aerojet has also designed and built an experimental solar electric propulsion system called NEXT-C, based on technology developed at NASA’s Glenn Research Center in Ohio.
Ed Reynolds, DART project manager at APL, said the NEXT-C xenon ion thrusters were powered for a two-hour in-flight test. Mission managers detected an unexpected interaction with the spacecraft, and later determined that the propulsion system could produce more than 100 amperes of current in a rare reset scenario.
“It was something we didn’t test to prove we could handle it,” Reynolds said. After analyzing the data, the mission team decided not to use the NEXT-C thrusters again unless DART missed its mark and had to prepare for a second attempt two years later, he said.
Fortunately, task managers didn’t have to follow this backup plan – now that engineers know the reset scenario, they’ll be able to align it with future applications of the NEXT-C ion propulsion system.
Update 9:35PM PT Sep 26th: Google has come up with a new way to celebrate the success of DART: