New Horizons completes flyby of Ultima Thule

LAUREL, Md. — NASA’s New Horizons completed a close approach to a small body in the distant Kuiper Belt early Jan. 1, collecting data that may reveal new insights about the formation of the solar system.

New Horizons made its closest approach to 2014 MU69, also known as Ultima Thule, at 12:33 a.m. Eastern, passing approximately 3,500 kilometers from the Kuiper Belt object. While the approach was celebrated at the time during an event at the Johns Hopkins University Applied Physics Laboratory (APL) here, the spacecraft was not in communications with the Earth.

NASA’s Deep Space Network received a signal from the spacecraft at 10:30 a.m. Eastern. That initial transmission contained no science data but rather telemetry about the health of the spacecraft and its performance during the flyby, including how much data it collected. Future downlinks, including one scheduled for later Jan. 1, will start returning science data.

“We have a healthy spacecraft,” said Alice Bowman, the New Horizons mission operations manager, after reviewing that initial burst of telemetry from the spacecraft, 6.6 billion kilometers from the Earth. “We’ve just accomplished the most distant flyby. We are ready for Ultima Thule science transmission.”

Prior to closest approach, project officials were optimistic that the spacecraft would perform the flyby as planned. “We’re very confident in the spacecraft and very confident in the plan that we have for the exploration of Ultima,” said Alan Stern, principal investigator for New Horizons, at a Dec. 31 press conference. “But I’d be kidding you if I didn’t tell you that we’re also on pins and needles to see how this turns out.”

Stern emphasized the uncertainties associated with the flyby and the inability to deal with any problems as the spacecraft is pushed to its limits. He said the Ultima Thule flyby was “much more challenging” than the one the spacecraft performed of Pluto in July 2015.

“We only get one shot at it. Nothing like this has ever been done before,” he said. “With any enterprise like this there comes risk. Fortunately, the rewards are work the risk.”

The rewards will come over the next 20 months as New Horizons slowly transmits the estimated seven gigabytes of data collected during the flyby. That data includes high-resolution images of Ultima Thule and spectra that can provide information about its composition.

What makes Ultima Thule interesting to scientists is that is part of a population of “cold classical” Kuiper Belt objects whose orbits, with low inclinations and eccentricities, suggest that they are pristine objects unaltered since the formation of the solar system 4.6 billion years ago.

“Nothing has happened to these things since they formed,” said John Spencer, a member of the New Horizons science team, at a pre-flyby briefing. “It’s a very special region that we’re very excited to explore.”