Dawn mission on the asteroid belt ends


WASHINGTON – A NASA spacecraft that has visited two of the largest objects in the Solar System’s main asteroid belt is running out of fuel, ending its mission, NASA said on November 1.

NASA announced that the Dawn spacecraft was silent during two communications sessions on the Deep Space Network on October 31 and November 1. After ruling out other possible causes for the lack of transmissions, officials concluded that the spacecraft ran out of hydrazine fuel for its attitude. control the thrusters, preventing it from maneuvering to point its main antenna towards the Earth or its solar panels towards the sun.

This lack of maneuverability ends the spacecraft’s mission, as expected. Project officials had warned for months that the mission would likely end this fall based on estimates of the remaining hydrazine on the spacecraft.

“In our current uncertainty, there are no usable hydrazines left,” said Marc Rayman, chief engineer and mission director for Dawn at the Jet Propulsion Laboratory, in a presentation on October 4 at the International Astronautical Congress in Bremen, in Germany. At the time, he said the spacecraft would likely run out of fuel by mid-October.

Dawn, built by Orbital Sciences Corp. (now Northrop Grumman Innovation Systems), launched in 2007 as part of NASA’s Discovery program of low-cost planetary science missions. The spacecraft, powered by electric thrusters, entered orbit around the great main asteroid belt Vesta in July 2011. After leaving Vesta in September 2012, Dawn entered orbit around Ceres, the dwarf planet which is the largest object in the main asteroid belt, in March. 2015.

Dawn remained in orbit around Ceres for the remainder of her mission, although mission officials at one point offered to leave orbit to fly over another asteroid. NASA chose to keep Dawn in Ceres and fly in different orbits around her, including her final orbit which brought the spacecraft within 35 kilometers of the planet’s surface.

The data collected by Dawn has helped scientists better understand the two worlds, as well as broader questions about the formation and evolution of the solar system. Ceres’ observations in particular indicated that he might once have, and may still have today, an underground ocean of liquid water.

“Dawn’s data sets will be deeply exploited by scientists working on how planets grow and differentiate, and when and where life might have formed in our solar system,” said Carol Raymond, principal investigator at Dawn to JPL, in a press release. “Ceres and Vesta are also important for the study of distant planetary systems, as they provide insight into the conditions that may exist around young stars.”

With her hydrazine depleted, Dawn will remain in orbit for decades before finally crashing to the surface of Ceres. NASA said there is a more than 99% chance that the spacecraft will stay in orbit for at least 50 years.

“The demands we put on Dawn were enormous, but they rose to the challenge every time,” Rayman said in the statement. “It’s hard to say goodbye to this amazing spaceship, but it’s about time.”

The end of the Dawn mission comes two days after NASA announced the end of another mission, Kepler. Both spacecraft ended their missions because they ran out of hydrazine fuel needed for attitude control, and both had experienced reaction control wheel failures earlier in their missions, causing them to fail. forced them to depend more on their thrusters than initially planned.

Despite the similarities, there was little interaction between the two missions as their spacecraft used the last of their hydrazine. “Our fuel requirements were different from theirs,” Charlie Sobeck, project systems engineer for Kepler at NASA’s Ames Research Center, said in an Oct. 30 briefing on the end of this mission. “We had more communication with Dawn about the jet wheels than about the fuel.”

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