New Horizons pushing the frontier ever deeper into the Kuiper Belt

New Horizons is healthy and performing perfectly as it flies deeper and deeper into the Kuiper Belt! Recently we conducted an engineering review of the spacecraft to "trend" how it was working compared to when it was launched. The result was amazing: Every system and science instrument aboard New Horizons is working as well as it did when we lifted off, more than 14 years and almost 5 billion miles ago. As mission principal investigator I could not be prouder - the men and women who designed, built and tested New Horizons literally created a masterpiece of American workmanship that will likely be able to perform and explore for many more years and many more miles! Before I update you on mission news, I want to highlight something cool on our mission website. There's a crazy amount of detail there for anyone interested in knowing more about the New Horizons mission and our scientific discoveries, but we've also posted a file to create 3D spacecraft models. With this file anyone with access to a 3D printer can create their own New Horizons to have at home or at work! Now for some mission happenings, starting with a cool public engagement project we're doing this month and next. As I mentioned, New Horizons is almost 5 billion miles from Earth. That is so far away, that the very closest stars appear in different positions in the sky than they do from Earth. This is due to the different perspective New Horizons has of these stars from its far away perch.

On April 22 and 23, New Horizons will image two of the closest stars, Proxima Centauri and Wolfe 359. Here on Earth, astronomical observatories and amateur observers will simultaneously take images of the same stars. Using software to combine imagery from the spacecraft and the ground, we'll be able to produce stereo images of these star fields showing each star "popping out" because of the "parallax," or changed perspective, between Earth and New Horizons.

Nothing like this has ever been accomplished before! We'll release these 3D images in May, so stay tuned. But in the meantime, details on how you can take part in this experiment are on the mission website.

My first mission news update is that this summer, we'll be using a trio of the largest telescopes on Earth, specifically, the Japanese Subaru telescope, and the U.S. Gemini and Keck telescopes to discover new Kuiper Belt Objects (KBOs) for New Horizons to study. We expect to literally find hundreds of new KBOs! Most of these will be too far to study from New Horizons, but a few dozen will be close enough for the spacecraft to image.

Although the objects will just be points of light in the distance, millions or even tens of millions of miles from our spacecraft, New Horizons images will be valuable for studying their surface properties, their satellite systems, their shapes and their rotations in ways that cannot be accomplished from Earth - owing to their great distance and our limited viewing angles from the inner solar system.

New Horizons has been conducting studies of KBOs like this since 2016, but we've only been able to find and study about 20 so far. With discoveries from the Gemini, Subaru and Keck telescopes, we hope to triple or even quadruple that number, greatly enhancing our scientific return from the Kuiper Belt.

We will also scour the set of newly discovered KBOs for any that New Horizons might be able to fly by, as we did with the KBO Arrokoth early last year. Computer models indicate the probability of finding another close flyby target is small, because we have so little fuel on board to divert toward such a flyby - but that won't stop us from looking! Our fondest hope is that we get lucky and have the opportunity for one more close flyby of a KBO. After all, no other spacecraft is exploring (or ever has explored) the Kuiper Belt, and none are on the drawing board to do so. This is humankind's best chance to get such a close up of another KBO for decades to come!

I also want to update you on another cool development for the mission: We are looking at how to increase the capabilities of New Horizons' instrument payload through software upgrades. The team is evaluating several cost and capability- increase options for six of the seven instruments, and we expect to decide which ones to implement in May. By about this time next year, these "flight software" changes will be made, tested and sent to New Horizons for us to begin using those new capabilities. Later this year, once we've selected which enhancements to implement, I'll describe each of them.

I'll close with some scientific news. First, I want to announce the forthcoming publication late this year or early next of a 1,000-plus page technical research volume called The Pluto System After New Horizons. This book, to be published in the distinguished University of Arizona Space Science Series, will contain 24 chapters detailing essentially every aspect of what was learned about Pluto and its moons from the historic first-ever flyby exploration of Pluto, which New Horizons conducted in July 2015.

All 24 chapters are now written, each by a team of scientific experts. Some have already completed review by other scientists to improve them, while others are undergoing that step. By May or June, we expect all 24 chapters to be in production for publication. The book should then be published about six months later.

The other science news I want to relay is about a blockbuster discovery this mission made as a result of its close flyby of the Arrokoth. We published the first indications of this discovery in the esteemed research journal Science in 2019; a much deeper analysis confirming the early results was published in Science this February. The discovery is about how Arrokoth, and by inference most other primordial "planetesimals" (or planetary building blocks), came into existence.

For many years, two competing mathematical models of planetesimal formation existed. The data from New Horizons shows, definitely, that only one of these models - variously called the "streaming instability" or "pebble cloud collapse" model - can produce an object like Arrokoth. Our evidence? The detailed shape, geology and alignment of the two halves, or "lobes" of Arrokoth.

The New Horizons images, compositional spectra, and color data on Arrokoth all point to this model being how Arrokoth formed. We summarized this discovery in a Feb. 13 press release. This may be the single most impactful discovery of the entire New Horizons mission so far, pointing to how planets got their start while settling what has literally been a decades-long computer modeling duel between competing theories.

And with that big news, I'll conclude this report. I'll write again this summer. Meanwhile, I hope you'll keep on exploring - just as we do!

SwRI-led New Horizons research indicates small Kuiper Belt objects are surprisingly rare

Using New Horizons data from the Pluto-Charon flyby in 2015, a Southwest Research Institute-led team of scientists have indirectly discovered a distinct and surprising lack of very small objects in the Kuiper Belt. The evidence for the paucity of small Kuiper Belt objects (KBOs) comes from New Horizons imaging that revealed a dearth of small craters on Pluto's largest satellite, Charon, indicating that impactors from 300 feet to 1 mile (91 meters to 1.6 km) in diameter must also be rare. The Kuiper Belt is a donut-shaped region of icy bodies beyond the orbit of Neptune. Because small Kuiper Belt objects were some of the "feedstock" from which planets formed, this research provides new insights into how the solar system originated. This research was published in the March 1 issue of the prestigious journal Science. "These smaller Kuiper Belt objects are much too small to really see with any telescopes at such a great distance," said SwRI's Dr. Kelsi Singer, the paper's lead author and a co-investigator of NASA's New Horizons mission. "New Horizons flying directly through the Kuiper Belt and collecting data there was key to learning about both large and small bodies of the Belt." "This breakthrough discovery by New Horizons has deep implications," added the mission's principal investigator, Dr. Alan Stern, also of SwRI. "Just as New Horizons revealed Pluto, its moons, and more recently, the KBO nicknamed Ultima Thule in exquisite detail, Dr. Singer's team revealed key details about the population of KBOs at scales we cannot come close to directly seeing from Earth."

Craters on solar system objects record the impacts of smaller bodies, providing hints about the history of the object and its place in the solar system. Because Pluto is so far from Earth, little was known about the dwarf planet's surface until the epic 2015 flyby.

Observations of the surfaces of Pluto and Charon revealed a variety of features, including mountains that reach as high as 13,000 feet (4 km) and vast glaciers of nitrogen ice. Geologic processes on Pluto have erased or altered some of the evidence of its impact history, but Charon's relative geologic stasis has provided a more stable record of impacts.

"A major part of the mission of New Horizons is to better understand the Kuiper Belt," said Singer, whose research background studying the geology of the icy moons of Saturn and Jupiter positions her to understand the surface processes seen on KBOs.

"With the successful flyby of Ultima Thule early this year, we now have three distinct planetary surfaces to study. This paper uses the data from the Pluto-Charon flyby, which indicate fewer small impact craters than expected. And preliminary results from Ultima Thule support this finding."

Typical planetary models show that 4.6 billion years ago, the solar system formed from the gravitational collapse of a giant molecular cloud. The Sun, the planets and other objects formed as materials within the collapsing cloud clumped together in a process known as accretion. Different models result in different populations and locations of objects in the solar system.

"This surprising lack of small KBOs changes our view of the Kuiper Belt and shows that either its formation or evolution, or both, were somewhat different than those of the asteroid belt between Mars and Jupiter," said Singer.

"Perhaps the asteroid belt has more small bodies than the Kuiper Belt because its population experiences more collisions that break up larger objects into smaller ones."

New Horizons Wakes for Historic Kuiper Belt Flyby

NASA's New Horizons spacecraft is back "awake" and being prepared for the farthest planetary encounter in history - a New Year's Day 2019 flyby of the Kuiper Belt object nicknamed Ultima Thule. Cruising through the Kuiper Belt more than 3.7 billion miles (6 billion kilometers) from Earth, New Horizons had been in resource-saving hibernation mode since Dec. 21. Radio signals confirming that New Horizons had executed on-board computer commands to exit hibernation reached mission operations at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, via NASA's Deep Space Network at 2:12 a.m. EDT on June 5. Mission Operations Manager Alice Bowman of APL reported that the spacecraft was in good health and operating normally, with all systems coming back online as expected. Over the next three days, the mission team will collect navigation tracking data (using signals from the Deep Space Network) and send the first of many commands to New Horizons' onboard computers to begin preparations for the Ultima flyby; lasting about two months, those flyby preparations include memory updates, Kuiper Belt science data retrieval, and a series of subsystem and science-instrument checkouts.

In August, the team will command New Horizons to begin making distant observations of Ultima, images that will help the team refine the spacecraft's course to fly by the object.

"Our team is already deep into planning and simulations of our upcoming flyby of Ultima Thule and excited that New Horizons is now back in an active state to ready the bird for flyby operations, which will begin in late August," said mission Principal Investigator Alan Stern, of the Southwest Research Institute in Boulder, Colorado.

New Horizons made a historic flight past Pluto and its moons on July 14, 2015, returning data that has transformed our view of these intriguing worlds near the inner edge of the Kuiper Belt. Since then, New Horizons has been speeding deeper into this distant region, observing other Kuiper Belt objects and measuring the properties of the heliosphere while heading toward the flyby of Ultima Thule - about a billion miles (1.6 billion kilometers) beyond Pluto - on Jan. 1, 2019.

New Horizons is now approximately 162 million miles (262 million kilometers) - less than twice the distance between Earth and the Sun - from Ultima, speeding 760,200 miles (1,223,420 kilometers closer each day. Follow New Horizons on its voyage at http://pluto.jhuapl.edu/Mission/Where-is-New-Horizons/index.php.

Long-Distance Numbers

On June 5, 2018, New Horizons was nearly 3.8 billion miles (6.1 billion kilometers) from Earth. From there - more than 40 times the distance between the Earth and the Sun - a radio signal sent from the spacecraft at light speed reached Earth 5 hours and 40 minutes later.

The 165-day hibernation that ended June 4 was the second of two such "rest" periods for the spacecraft before the Ultima Thule flyby. The spacecraft will now remain active until late 2020, after it has transmitted all data from the Ultima encounter back to Earth and completed other Kuiper Belt science observations.

The PI's Perspective: Why Didn't Voyager Explore the Kuiper Belt?

New Horizons is in good health and cruising closer each day to our next encounter, an end-of-the-year flyby of the Kuiper Belt object (KBO) 2014 MU69 (or "MU69" for short). Currently, the spacecraft is hibernating while the mission team plans the MU69 flyby. During hibernation, three of the instruments on New Horizons-SWAP, PEPSSI and SDC-collect data every day on the charged particle, ionized plasma and dust environment in the Kuiper Belt at a solar distance of 41-42 astronomical units (AU), where our spacecraft is traveling. (1 AU is the distance from the Earth to the Sun, about 93 million miles or 140 million kilometers; for comparison, Pluto is about 34 AU from the Sun, so we're about 750 million miles farther out than Pluto now.) A role of all NASA mission principal investigators is to communicate with the public. I typically give 20 to 30 public New Horizons talks per year, and a question I used to get a lot is whether Voyager could have explored Pluto. I addressed that really interesting question in this column in June 2014, shortly before our Pluto encounter began.

Now people often ask why the Voyagers didn't explore the Kuiper Belt, since both Voyager 1 and 2 clearly transited this region after passing the giant planets. That's a really good question with a number of facets, so I thought I'd address it in this PI Perspective.

Our New Horizons extended mission to explore the Kuiper Belt and KBOs runs to mid-2021, when the spacecraft will be at a distance of 50 AU. This mission consists of three primary scientific investigations: studying the ionized plasma and dust environment of the Kuiper Belt with our charged-particle and dust sensors, studying numerous KBOs in the distance with our Long Range Reconnaissance Imager (LORRI), and exploring one ancient KBO (2014 MU69) in a close flyby.

Voyager carried many spectacular instruments through the Kuiper Belt, including imagers, spectrometers, magnetometers and charged-particle detectors. Those instruments have contributed a lot to our understanding of the Sun's heliosphere and the Kuiper Belt plasma environment, even though the Kuiper Belt wasn't discovered until 1992, when Voyager 1 was almost all the way across the region and Voyager 2 was deep within it. So even though the Voyager team didn't know their spacecraft was in the Kuiper Belt until 1992, the Voyagers themselves collected a lot of data about the region. Now, New Horizons is transiting the region with more advanced charged particle spectrometers and a dust detector, making new and more sensitive studies of this aspect of the Kuiper Belt's environment.

Regarding the images we're taking of KBOs our spacecraft passes in the distance, however, Voyager's imagers would have not been able to do what New Horizons can-such as search for KBO satellites, or determine KBO rotation periods and shapes. Why not? First, with very few known KBOs at the time, and certainly no small ones known close to Voyager's trajectory, it would have been impossible to put together a Kuiper Belt target observing list. But even had the team been able to somehow craft such a list, Voyager's cameras used older-technology Vidicon detectors instead of the charge-coupled devices (CCDs) that LORRI uses (and are found in most digital cameras). As a result, Voyager's imagers were not anywhere near as sensitive as those aboard New Horizons, and they could not have detected faint KBOs like the telescopic LORRI can.

But, perhaps most important is the question: could Voyager have flown by a small KBO as New Horizons will do this December and January? Again, regrettably, the answer is no, for a number of reasons. First, even once the Kuiper Belt had been detected in 1992, the Hubble Space Telescope (the only telescope capable of finding such distant flyby targets, even today) hadn't been repaired to properly focus light. That repair didn't occur until December 1993. By then, Voyager 1 was exiting the Kuiper Belt near 55 AU, and Voyager 2 was near 42 AU. But even after its repair, the Hubble wasn't sensitive enough to detect KBOs as small and common as MU69, so there would have been no way to find a flyby target-that capability only came in 2009, when a more advanced and sensitive wide-field camera was placed aboard the Hubble during a servicing mission.

And even if those limitations weren't the case, it might have been hard to find a KBO along the Voyagers' paths. That's because both Voyagers 1 and 2 traveled far out of the plane of the solar system, on which the heart of the Kuiper Belt resides. Unlike New Horizons, which is traveling directly through the densest region of the Kuiper Belt, the Voyagers were literally a billion or more miles above (Voyager 1) or below (Voyager 2) most of the KBO population; they were closer to the fringes of the population where there are fewer flyby candidates. Of course, had the Kuiper Belt been known in the 1980s, the Voyagers could have been targeted to fly through its heart, but that would have adversely affected the targeting of and scientific return from their final flybys at Saturn and Neptune, respectively, something I doubt the science teams would have favored because their prime objectives were to study the giant planets and their satellites.

It's too bad, because their cameras and spectrometers and other instruments could have made very nice observations of a flyby target had they been able to find one. But alas, there's wrinkle to that too: Voyager's cameras also weren't sensitive enough to navigate to a close flyby the way New Horizons can, snapping pictures to home in on MU69 even from distances of over 100 million miles (or 160 million kilometers), so it would have been very difficult to target a close flyby using Voyager. In sum, a Voyager KBO flyby was simply not in the cards, given the lack of knowledge of the Kuiper Belt back then, the Hubble's capabilities when Voyager crossed the region, the spacecraft trajectories and their onboard optical imaging and navigation limitations.

So, all in all, practical limitations meant that Voyager really could not have done the Kuiper Belt exploration mission New Horizons is now performing. But no matter, New Horizons is exploring the Kuiper Belt, and the Voyagers left an amazing legacy of truly opening our eyes to the giant planets and their rings, satellites and magnetospheres-both amazing outcomes!

I wonder when the next, even farther explorations will take place out in the Kuiper Belt, and how will people compare those future missions to what we accomplish with New Horizons?

Well, that's my update for now. For more mission news, stay tuned to the many websites and social media channels listed below.

I'll write again around the time we wake up New Horizons in early June. Until then, I hope you'll keep on exploring-just as we do!

New Horizons captures record-breaking images in the Kuiper Belt

NASA's New Horizons spacecraft recently turned its telescopic camera toward a field of stars, snapped an image - and made history. The routine calibration frame of the "Wishing Well" galactic open star cluster, made by the Long Range Reconnaissance Imager (LORRI) on Dec. 5, was taken when New Horizons was 3.79 billion miles (6.12 billion kilometers, or 40.9 astronomical units) from Earth - making it, for a time, the farthest image ever made from Earth. New Horizons was even farther from home than NASA's Voyager 1 when it captured the famous "Pale Blue Dot" image of Earth. That picture was part of a composite of 60 images looking back at the solar system, on Feb. 14, 1990, when Voyager was 3.75 billion miles (6.06 billion kilometers, or about 40.5 astronomical units [AU]) from Earth. Voyager 1's cameras were turned off shortly after that portrait, leaving its distance record unchallenged for more than 27 years. LORRI broke its own record just two hours later with images of Kuiper Belt objects 2012 HZ84 and 2012 HE85 - further demonstrating how nothing stands still when you're covering more than 700,000 miles (1.1 million kilometers) of space each day.

Distance and Speed

New Horizons is just the fifth spacecraft to speed beyond the outer planets, so many of its activities set distance records. On Dec. 9 it carried out the most-distant course-correction maneuver ever, as the mission team guided the spacecraft toward a close encounter with a KBO named 2014 MU69 on Jan.

1, 2019. That New Year's flight past MU69 will be the farthest planetary encounter in history, happening one billion miles beyond the Pluto system - which New Horizons famously explored in July 2015.

During its extended mission in the Kuiper Belt, which began in 2017, New Horizons is aiming to observe at least two-dozen other KBOs, dwarf planets and "Centaurs," former KBOs in unstable orbits that cross the orbits of the giant planets.

Mission scientists study the images to determine the objects' shapes and surface properties, and to check for moons and rings. The spacecraft also is making nearly continuous measurements of the plasma, dust and neutral-gas environment along its path.

The New Horizons spacecraft is healthy and is currently in hibernation. Mission controllers at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, will bring the spacecraft out of its electronic slumber on June 4 and begin a series of system checkouts and other activities to prepare New Horizons for the MU69 encounter.