New Horizons team gets ready for epic overview of Ultima Thule

KNOXVILLE, Tenn. – In less than 10 weeks, NASA's New Horizons mission will explore the farthest target ever visited by a spacecraft.

At dawn on January 1, 2019, New Horizons will ring early in the year by flying over the object of the Kuiper Belt (KBO), officially named MU69 2014 but nicknamed Ultima Thule, a rock of the size of a city considered a frozen relic. from the birth of the solar system.

Although scientists have a rough estimate of the size of Ultima Thule – about 37 km wide – they do not have much more information. They do not know if it is lying, whether it has a lunar or circular system or even if it 's only one object. Indeed, some very limited observations by Ultima Thule suggest that it could be two bodies in close orbit. [NASA’s New Horizons Mission in Pictures]

"We really do not know what to expect," said New Horizons principal investigator Alan Stern of the Southwest Research Institute in Boulder, Colorado, at a news conference held yesterday (October 24). at the Planetary Science Division of the American Astronomical Society. meeting.

But New Horizons should reveal the secrets of Ultima Thule, as the probe lifted the veil on Pluto during its historic flight over the dwarf planet in July 2015.

New Horizons will not only reveal information about Ultima Thule's size, surface, and possible orbital companions, it should also help planetary scientists understand how the solar system has formed, Stern said.

"Whatever we do, it will be historic," he said.

"A point in the distance"

The images of New Horizons approaching Pluto more than three years ago revealed more and more details about the distant dwarf planet. But do not expect the same thing to happen with Ultima Thule, which is much smaller than the 1,477-mile wide Pluto.

"Ten weeks from Pluto, we could already solve the disc, and every week we were waiting for more and more details," said Stern. "But Ultima Thule in ten weeks is only a point away, and it will remain so until the day before the flyby, when we begin to solve it."

On January 1st, New Horizons will look at Ultima Thule relatively briefly, zooming into the icy world at 20,000 mph (32,000 km / h). But scientists will make the most of the meeting. The seven scientific instruments of New Horizons will examine the KBO, looking for clues about its composition or signs of cometary activity on its surface. A high resolution camera will explore the surface and the spacecraft will measure the rotation properties of Ultima Thule.

After the visit of New Horizons to Pluto, the probe fell asleep for a moment. But the clock truly rebooted in June 2018, when spacecraft particle detection instruments began to make observations. The team has also begun conducting readiness tests to ensure that the spacecraft is ready for New Year's flight.

During the press conference, Hal Weaver, a member of the New Horizons team at the Johns Hopkins Applied Physics Laboratory (APL), told Hal Weaver in late November and early December "we're going to make some observations very intensive environment around Ultima Thule ".

These preliminary observations will look for moons, rings of dust or debris that could damage the spacecraft during its overflight. The team has until Dec. 16 to decide if they want to make the close flyover they expect (2,175 miles or 3,500 km from the surface of the object) or re-launch Thule from a safer distance (6,200 miles) or 10,000 km), Weaver added. [Kuiper Belt Objects: Facts about the Kuiper Belt & KBOs]

In perspective, New Horizons was established within 12,500 km of Pluto in July 2015.

"We can still have a fantastic mission, but avoid damaging the spaceship," Weaver said.

The final images that New Horizons transmits home before the close encounter will be comparable to the NASA Hubble Space Telescope preview that can currently capture Pluto, said Weaver, an image representing only a handful of pixels.

"Wait after that, it is at that time that the very rich data set will fall," he said.

Once the spacecraft has oriented its instruments on Ultima Thule, New Horizons will no longer be able to communicate with the Earth. And the probe will continue to study the KBO for a spell after the closest approach, staying locked to measure the object's nighttime temperatures, which can reveal information about how the heat is moving. on its surface. Plasma and dust sensors will also measure the immediate environment of Ultima Thule.

Stern and his colleagues are not expecting to see an atmosphere or a sign of the current geological processes on the tiny rock, but he says that they will look anyway.

"If we found recent activity in such a small object, we would make headlines because we would not understand how it could happen," Stern said.

A few hours after the close encounter, the probe will turn and send home a signal to inform her fans on Earth that she has survived her attempt with Ultima Thule. The signal will take more than 12 hours to reach the control of the mission, said members of the mission team.

On January 2nd and 3rd, New Horizons will return some of the best images and overflight measurements. The photos will present a resolution even greater than those taken by Pluto, said the mission team. [Pluto Flyby Anniversary: The Most Amazing Photos from NASA’s New Horizons]

It took about 16 months for New Horizons to return all the data from the meeting with Pluto. Getting all the images of Ultima Thule on the floor will take even more time.

"The data will be available until 2019 and until 2020," Stern said.

The spacecraft will transmit the 50 gigabytes of data it collects during flyby to just over 1,000 bits per second. Carey Lisse, another researcher from New Horizons, also from APL, compared this experience to the former of numbering, where images were loaded row by row.

"Except that you were not telephoning at a distance of 4 billion kilometers," Stern said.

& # 39; Far & # 39;

Stern said that "Ultima Thule" is a Latin word meaning "beyond the farthest borders", which is certainly the case of the icy rock. Not only is it farther away than any cosmic object ever explored – more than 40 times farther from the sun than Earth's orbits – but it will also be the first object studied at the bottom of the Kuiper Belt.

"This will be our first truth on the ground, our first careful examination of what makes these [Kuiper Belt] Kelsi Singer, a member of the New Horizons team, also a member of SWRI, said at today's press conference: "This will be important for understanding these objects."

Understanding the ice on the edge of the solar system will tell us a lot about our own world. The Kuiper Belt contains the remains of matter after the end of the formation of the planet. By studying Ultima Thule, we will have a glimpse of the same ingredients that helped build the Earth and its siblings, Stern said.

"New Horizons will have the ability, in the space of one week, the first week of January 2019, to confirm or refute the models themselves. [of solar system formation] presented here at the meeting of the Division of Planetary Sciences, "said Stern.

The flyby should also help solve a mystery about the surprising brightness of the KBO. Like most rocky objects in the outer solar system, Ultima Thule is almost as dark as coal, despite its ice shell. That's because it's been cooked by cosmic radiation for centuries, said Lisse. But Ultima Thule is a little brighter than it should be.

"Something is happening that makes it twice as bright as your average comet nucleus," Lisse said. Let's hope that New Horizons discovers what makes the small target shine.

Scientists still do not know what New Horizons will reveal when it reaches Ultima Thule in just a few weeks. But they are eager to unveil the secrets of the solar system.

"There is one thing you can say about Ultima Thule for sure," said Stern. "It's far away."

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