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NASA's New Horizons spacecraft goes to a New Year meeting with a distant world – Spaceflight Now


The artist's concept of the New Horizons spacecraft approaches the Kuiper Belt Object. Credit: NASA / JHUAPL / SWRI

Three years and a billion miles past Pluto, NASA's New Horizons investigation is on the verge of at least one pioneering milestone, once in a lifetime: a New Year's Day flyby from a small body known as 2014 MU69, unofficially dubbed Ultima Thule – "in outside the known world "- in the NASA naming contest.

Like Pluto, Ultima Thule (pronounced TOO-lee) is a remote Kuiper Belt inhabitant, a vast area outside Neptune's orbit inhabited by countless dwarf planets and the remaining frozen reservoirs left from the birth of the 4.6 billion solar system many years ago.

Slightly more than a dimmer of light even for the Hubble Space Telescope, Ultima Thule will be the farthest object that has been directly explored, a record that will likely last for decades to come if not again.

If all goes well, New Horizons will race against its target at a speed of 32,000 mph – almost nine miles per second – at 12:33 on New Year's Day, passing around 2,200 miles from the surface of Ultima Thule that hasn't been seen.

Four hours later, the spacecraft will turn around to direct the satellite dish on Earth to confirm a successful meeting. A few hours after that, the first high-priority image and other data will start running back to the inner solar system.

"Throughout the team, people are ready, they are in the game, we can't wait to go exploring," Alan Stern, New Horizons lead investigator, said on Friday. "It's been three and a half years (since Pluto fly), we have worked very hard, people are ready to see the results and see what we can learn about the birth of our solar system."

At a distance of 4.1 billion miles from Earth, Ultima Thule will take radio signals, travel 186,000 miles per second, six hours seven minutes and 58 seconds to cross the bay to scientists waiting at the Johns Hopkins University Applied Physics Laboratory near Baltimore. The first high-resolution image is expected to be launched at the January 2 briefing.

Even though the government closure is underway, the public is expected to be able to follow NASA's satellite television channel. But just in case, the Applied Physics Laboratory, which builds and operates New Horizons for NASA, plans to send pictures and other data on the New Horizons web page and laboratory YouTube channels.

Only a few images and other high-priority data are expected before New Horizons moves behind the sun as seen from Earth on January 4, temporarily disrupting communication. But even when the downlink continues, it takes around 20 months to bring the entire treasure to Earth.

That's because of the great distance, the faint signal from the New Horizons 30-watt transmitter and other demands on NASA's Deep Space Network antenna that reaches the entire world that is used to communicate with spacecraft across the solar system.

For scientists who want to study the untouched remains of the original clouds of rocky debris that combine to form the solar system, the long wait will be in vain.

"Everything we've visited before has warmed up at some point," Stern said in an interview earlier this month. "Asteroids orbit near the sun, comets … are born cold, but we only visit comets when they descend near Earth's orbit, when they are warm. Heat, warmth causes chemical reactions to occur, can drive surface processes, etc., which creates evolution. "

Ultima Thule, he said, "was not at all marked by these things." It is classified as a "cold classic," that is, the Kuiper Belt body with an almost circular orbit that is only slightly tilted to the sun's plane. planetary systems. Another major population of the Kuiper Belt body, consisting of material originating closer to the Sun, is pushed out by gravitational interactions in the distant past.

But not for cold classics and Ultima Thule.

"He was born four billion miles from the sun, always there, the temperature is almost above absolute zero," said Stern. "I do not believe there are any objects that we have visited that remain cold during their existence. So this is really a time capsule, that's the scientific value. "

Stron Horizon will fly more than twice closer to Ultima Thule than on Pluto, Stern said, "so the picture will be much more detailed."

"We will find out how this object is built, how much it evolved, made of what, if it has an atmosphere, if it has a moon, if it has a ring, we will measure its temperature, we will measure the reflectivity of the radar, we will find out whether it is surrounded by clouds the remaining dust from the formation, "he said.

"All that and much more, because we will not only take the image," he added. "We map the surface, we map it in color and besides that, we map it in stereo so we have topography everywhere. Not only will we determine the composition, but we map it from one place to another to see if the composition is the same everywhere or if it consists of smaller building blocks.

The meeting had five main objectives: to characterize the geology, morphology and topology of Ultima Thule; to map the color and composition of its surface; to determine its structure; to search for satellites and rings; and to look for any kind of comma, or atmosphere.

"Ultima Thule can be very crater, very pitted or even smooth from ancient streams and ancient activities," said Carey Lisse, collaborator of the New Horizons science team. "We don't know. We won't know until we get there in January. I'm waiting to be surprised."

Launched almost 13 years ago in January 2006, New Horizons flew past Jupiter in February 2007, using a giant planet as a target to test its instruments and, more importantly, use gravity to fly planes to fast track trails to Pluto.

Even so, moving 100 times faster than jet planes along the way, it still takes eight more years to reach the target in July 2015, flying over a distance of 7,800 miles to collect the first close-up images and lots of data about the most famous dwarf planets in the solar system.

Pluto's global mosaics are made from images from the New Horizons flyby spacecraft in July 2015. Credit: NASA / JHUAPL / SWRI

While the Pluto meeting is the spacecraft's main goal, the mission manager knows it will leave propellant and that its nuclear power supply will make the probe function until the 2020s. Long before Pluto's flyby, the team requested an observation of time at the Hubble Space Telescope to look for possible target targets past Pluto which might be quite close to the New Horizons trajectory to allow other flyby.

Hubble discovered Ultima Thule in a picture taken on June 26, 2014. He was categorized as 2014 MU69 and was given a small planet number 485968. Analysis of its orbit showed that New Horizons could achieve it with a post-Pluto track correction maneuver.

After the Pluto meeting was completed, NASA managers agreed to extend the mission. Carefully planned rocket shootings, adjusting the New Horizon lane to arrange upcoming meetings with Ultima Thule.

New Horizons did not find the mine until August 15 this year, at a distance of more than 100 million miles. It is a point of light that is barely visible, and will remain a little more from bright spots until Monday, the day before flying.

Even so, scientists have at least some idea what to expect when New Horizons gets there. Based on occult observations where Ultima Thule passed in front of a background star as seen from Earth, the researchers believe the target is an elongated body measuring around 17 miles. This can consist of two objects in a close orbit or two physically connected lobes, called "binary contacts."

Researchers know Thule Ultima only receives about 0.05 percent of the sunlight that the Earth does and they know the color is reddish. But they don't know the exact dimensions, whether they have any rings, moons, or atmospheric traces.

"Really, we don't know what to expect," Stern told planetary scientists during a conference in October. "We only discovered it in 2014 with the Hubble Space Telescope working at the limit of its fantastic capabilities. We have learned enough about its orbit to be able to intercept it and target it. But we know very little. "

Whatever they find, it will happen very, very quickly. The small size of Ultima Thule means the New Horizons camera will not finish until a day before the meeting.

On Sundays, for example, the best photos will have a resolution of about 6.2 miles per image element, or pixels, and Ultima Thule will be two to three pixels in size. On New Year's Eve, the resolution will increase to 3.4 miles per pixel and the size of the body will reach five to six pixels.

But on the eve of New Year's Day, the resolution will increase to 1,000 feet per pixel and the day after, 500 feet per pixel with Ultima Thule which stretches up to 215 pixels.

"Even though we travel at the same speed as we passed Ultima that we passed Pluto, Pluto is about the size of a continent like North America," said Stern. "So, when we were 10 weeks out of Pluto, we were able to complete the disk as well as the Hubble Space Telescope, and every week we could see more and more detail.

"But the 10-week Ultima came out just in the distance. And it will remain as a point in the distance until literally the day before flying when we begin to finish it. The day after flyby, we will have high resolution images, we hope the resolution is higher than the best image of Pluto. So it will be fast. "

New Horizons is equipped with six main instruments: an imaging spectrometer known as Alice, a multi-spectral light camera called Ralph, LORRI – which combines 8-inch telescopes, solar wind particle detectors, particle spectrometer energy detectors and dust counters made by students.

In addition, the radio system includes circuits that allow analysis of changes that occur accurately when signals from Earth pass through the atmosphere.

Data is stored on an eight-gigabyte solid-state recorder and sent back to Earth with an X-band transmitter using a fixed 83-inch parabolic antenna. Data transmission speed will be slightly better than 1,000 bits per second.

Stern said the meeting was a far more difficult challenge for New Horizons than Pluto.

"This is more difficult for a number of different reasons. First of all, it's smaller and dimmer so it's hard to track, it's harder to get at home, "he said. "It's 100 times smaller, 10,000 times fainter. Second, every year, the supply of nuclear power on ships produces less power. So now we have to be more careful about managing instruments and which avionics are active, we must manage our strength more hearted -heart. "

This Ultima Thule image, or 2014 MU69, was captured by the Hubble Space Telescope in 2014. Credit: NASA / JHUAPL / SWRI

Thirteen years after its launch, a single thermoelectric radioisotope thermoelectric generator, or RTG, produces only about 190 watts of power, roughly enough to energize three standard light bulbs.

In addition, because the science team doesn't know what to expect, New Horizons will carefully search the area around Ultima Thule, to search for the moon or other features, so "there will be lots of empty sky images just because we try to cover the entire area if we found the moon late. "

Four days after flyby, communication with New Horizons will be delayed as the spacecraft moves behind the Sun as seen from Earth. The science team has prioritized data playback to ensure high-resolution Ultima Thule images reach Earth before blackouts begin.

"This is a much faster disclosure than anything we did on New Horizons before," Stern said. "Basically, this is an overnight conversion from the point in to the real world. And I think the first week of January, when we get the first detailed image back, will be amazing! Not only scientifically. I think for people who follow the news only to see and think about what our race can do, what our species can do, will be extraordinary. "

Asked whether New Horizons could reach the third Kuiper Belt target at the end of the road, Stern said he wanted his team to remain focused on Ultima Thule in the near future. But after the meeting was over, "we will look for another flyby target. I can't promise anyone, you or NASA, that we will find one (but) I can tell you this: there is nothing my team wants besides getting the second one. "

Editor's note: Parts of this story were originally written for Astronomy magazine Now and are used here with permission.

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