New Horizons signals successful flyby of Ultima Thule
LAUREL, Md — While many around Earth were ringing in the new year, a group of scientists and engineers celebrated the moment a tiny spacecraft raced by a small world, virtually unknown, to complete the farthest exploration of any Solar System object.
At 12:33 a.m. EST (05:33 GMT) Jan. 1, 2019, New Horizons, having flown by Pluto 3.5 years and 1 billion miles ago, zipped past Kuiper Belt object 2014 MU69, also known as Ultima Thule at about 32,000 mph (51,500 kph). At its closest approach it was a mere 2,200 miles (3,500 kilometers) from its surface.
Ringing in 2019 with the farthest flyby ever
Approximately 1,000 people celebrated the moment of the flyby at Johns Hopkins University’s Applied Physics Laboratory (JHUAPL) Kossiakoff Center on New Year’s Eve. The festivities featured two countdowns, one to midnight, and the other to closest approach.
Two minutes after midnight, astrophysicist and Queen guitarist Brian May wowed the crowd with a video debuting a new song he wrote for New Horizons. May is also a member of the mission team.
While training its seven science instruments on Ultima Thule to collect data, New Horizons could not communicate with Earth. As done at Pluto in July 2015, a last photo taken of Ultima Thule before the flyby was sent back to assure at least some return on the mission in the event the spacecraft was destroyed by debris and unable to complete the flyby.
After the closest approach, New Horizons was not scheduled to call home for another several hours. Even then, the signals still took another six hours to reach tracking stations on Earth, arriving at approximately 10:30 a.m. EST (15:30 GMT).
Video courtesy of Queen Official
Guests and media returned to Kossiakoff Center later that morning, where they watched a live feed of the mission control room as the mission team waited for, then received the signal that all systems on the spacecraft are nominal.
In a panel discussion, New Horizons principal investigator Alan Stern of the Southwest Research Institute in Boulder, Colorado; mission operations manager Alice Bowman of JHUAPL; systems engineer Chris Hersman of JHUAPL; and project scientist Hal Weaver, also of JHUAPL, presented the pre-flyby image of Ultima Thule returned by the spacecraft and discussed mission scientists’ first impressions of the object.
“We’re here to tell you that last night the United States spacecraft New Horizons conducted the farthest exploration in the history of human kind, and it did so spectacularly, ” Stern said. “Thousands of operations on board the spacecraft had to work correctly in order for us to be able to tell you this, and now we know that it all did.
As expected, this first stream of data from the farthest encounter in human history was just a status check with the spacecraft letting those who operate it on Earth know that it survived the encounter. It also signaled it had a memory full of data, indicating that science objectives were likely accomplished.
Once the signals were sent by New Horizons, it resumed its final outbound science gathering. The next signal home is expected to be received by tracking stations on Earth sometime in the afternoon of Jan. 1. As of the post-flyby press conference, the signals with the new data, traveling at the speed of light, were about halfway in their six-hour journey from the spacecraft.
That data stream is expected to have the first images of Ultima Thule that are larger than the several-pixel fail-safe images sent earlier on Dec. 31.
Analyzing the data
“Even though it is a pixelated blob still, its a better pixelated blob that the day before,” said Hal Weaver, New Horizons project scientist, said of the pre-flyby image.
The low-resolution image taken from a distance of half a million miles reveals it to be an elongated object estimated to be 22 X 9.3 miles (35 X 15 kilometers). Irregularly shaped, it is either bi-lobate, meaning it has two lobes, or two objects in close orbit around each other that appear blurred together in the photo. Both possibilities were first raised during observations conducted when Ultima Thule occulted stars in 2017 and 2018.
In fact, Weaver said it was enough to resolve a pre-flyby puzzle. Ultima Thule, an elongated object, did not appear to change in brightness as it rotated as the spacecraft approached.
“Well, that’s because the pole is almost pointing toward the spacecraft,” Weaver said. “There is no change in brightness because we are always seeing the same side.”
So far, data is not sufficient enough for scientists to calculate a rotation period, Weaver said.
“This will all be revealed, either tomorrow or the next day,” Weaver said. “Ultima Thule will be turned into a real world. We’ll see the images tomorrow.”
According to Weaver, the object’s elongated shape is not a surprise as many small solar system bodies have this shape, one of which is Comet 67P/Churyumov-Gerasimenko.
High-resolution images from the flyby are expected to arrive later Jan. 1, and mission scientists plan to study them overnight before releasing them at a 2 p.m. EST (19:00 GMT) press conference on Jan. 2.
Color images will be returned later this week and will be combined with black-and-white images to provide a high-resolution image of Ultima’s appearance, Stern said. From these images, mission scientists should be able to learn a lot about the KBO’s geology.
Next week,the spacecraft will be in conjunction with the Sun and will be unable to send data back. Communications will resume in mid-January, and the highest resolution images are expected in February. It is expected to take some 20 months to receive everything at the spacecraft’s 1-2 kilobit per second rate.
Billions of miles in the making
New Horizons launched on Jan. 19, 2006, atop an Atlas V from Cape Canaveral Air Force Station’s Space Launch Complex 41 in Florida. Just over a year later, it used Jupiter as a gravity assist to shave three years off its travel time toward Pluto.
On July 14, 2015, after nine years and 3.6 billion miles (5.8 billion kilometers), the baby grand piano-sized spacecraft finally flew by Pluto at a distance of 7,800 miles (12,500 kilometers). It was the culmination of decades of work and the last of the classically-known nine planets to be explored (Pluto was reclassified as a dwarf planet in 2006).
While approaching Pluto, a search for another KBO to fly by was undergoing. Using a combination of ground-based telescopes and the Hubble Space Telescope, Ultima Thule — which means “beyond the known world” — was chosen on Aug. 28, 2015.
“When we confirmed that the flyby had been success it was emotionally huge for the New Horizons team because we had worked so many years at this one shot at exploring Ultima Thule. I could not be prouder of the men and women of New Horizons for what they accomplished for science, for exploration, and frankly for history, in this flyby,” Stern told SpaceFlight Insider.
Four course adjustment burns via New Horizons’ engine were required between Oct. 22 and Nov. 4, 2015, in order to target the unknown body.
Until Dec. 31, the KBO was only seen as a point of light. Using spectroscopy as well as several occultations of stars in 2017 and 2018, scientists were able to estimate its likely shape, size, color and brightness, but not much more.
Until the data starts returning to Earth, Ultima Thule will remain a mystery. But its secrets are expected to help scientists better understand the formation of the Solar System as the object is thought to be a pristine frozen remnant of the early Solar System some 4.6 billion years ago.
“The New Horizons team makes [the flyby] look easy,” Stern said of the Ultima Thule encounter. “It’s not easy. All these projects in spaceflight require enormous attention to detail and really smart and dedicated people.”
Stern said the New Horizons project is no exception as the team spent 3.5 years working to ensure everything would go according to plan.
“From everything we can tell,” Stern said, “they scored a 100 on the test.”
Derek Richardson contributed to this story
Video courtesy of JHU Applied Physics Laboratory
Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.