LAUREL, Md. — Even as NASA’s New Horizons spacecraft bears down on one object in the Kuiper Belt, the mission team is already thinking about a second potential flyby in the 2020s.
New Horizons will fly by 2014 MU69, nicknamed Ultima Thule, on Jan. 1, making its closest approach of about 3,500 kilometers at 12:33 a.m. Eastern. The spacecraft will not be in contact with Earth at the time of closest approach but will transmit a burst of “health and safety data” several hours later, arriving at Earth at 10:29 a.m. Eastern.
The Ultima Thule flyby is going according to plan, project officials said Dec. 31. “The spacecraft is on course, it’s healthy, it’s conducting observations as we speak,” said Alan Stern, principal investigator for New Horizons, during a press conference at the Johns Hopkins University Applied Physics Laboratory here Dec. 31.
While the near-term focus for the mission is the Ultima Thule flyby, project officials have started thinking about the possibility of sending New Horizons past another, as-yet undiscovered object in the Kuiper Belt, based on the projected levels of power from the spacecraft’s radioisotope thermoelectric generator and hydrazine fuel used for maneuvering.
“We have power and fuel to run this bird into the mid-2030s, maybe longer,” Stern said at a Dec. 28 briefing. “What the science team and the mission team want to do after we get all the data back from Ultima is to propose to NASA to explore the outer parts of the Kuiper Belt.”
One issue is finding a potential Kuiper Belt object for New Horizons to fly by. Discovering Ultima Thule required a concentrated effort using the Hubble Space Telescope, with astronomers finding it in 2014. Only Hubble and New Horizons itself have seen the object.
“To look for it we’ll use every tool that’s possible,” Stern said Dec. 30 of finding another Kuiper Belt object in reach of New Horizons. That includes large groundbased telescopes, Hubble and the future James Webb Space Telescope, he said.
That also includes New Horizons itself, using a spacecraft instrument called the Long Range Reconnaissance Imager, or LORRI. Stern noted that LORRI first saw Ultima Thule in August, at a distance of more than 160 million kilometers. The camera could have seen the object at an even greater distance, he noted. “We can use that camera to search for other objects that are crossing our path in the distance,” he said.
That will require new ways of using the camera, though. Hal Weaver, the project scientist for New Horizons, said changes to the flight software could allow LORRI to take hundreds of images and then combine them, returning only the combined image.
“The big bottleneck is being able to send data back,” he said, given the low bandwidth available at the spacecraft’s extreme distance from the Earth. “We can’t possibly take thousands of images and send those all back.”
That concept, Weaver added, is still in the “drawing board” stage of development. “We’ve got to focus on Ultima Thule right now,” he said. “But right after the flyby we’ll jump on this problem.”
While the Ultima Thule flyby was planned years in advance, a future flyby might take place only on a few months’ notice if the object is discovered by LORRI. “It can only see about six months in front of us,” Stern said. “What we’ll have to do is build a generic flyby mode and do a flyby on warning if we detect it from onboard the spacecraft.”
The project will also have to get NASA to approve another extended mission for the spacecraft. New Horizons is currently operating on one extended mission for the Ultima Thule running through 2021 at a cost of $81 million. That is in addition to the $720 million cost of New Horizons’ primary mission to fly by Pluto, which ran through 2017.
Stern said that the project will prepare a proposal for another extended mission in mid-2020 for the next senior review of planetary science missions. Work on that proposal, he said, will likely begin in mid-2019. “I’m not worried about a time crunch,” he said, as New Horizons will be in the Kuiper Belt likely until the late 2020s and will be operational for even longer.
But first, he emphasized, is the Ultima Thule flyby. “I’ve been trying to keep people from thinking about that,” he said of a second flyby, “and be focused on Ultima.”