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!

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!

Wrapping up 2017 one year out from MU69

New Horizons is in good health and cruising closer each day to its next encounter: a flyby of the Kuiper Belt object (KBO) 2014 MU69 (or "MU69" for short). If you follow our mission, you likely know that flyby will occur on New Year's Eve and New Year's Day 2019, which is just barely over a year from now! As I write this, New Horizons is wrapping up an active period that began when the spacecraft emerged from hibernation mode in September. But soon, on Dec. 21, we'll put the spacecraft back in hibernation, where it will remain until June 4, 2018. After June 4 the spacecraft will stay "awake" until late in 2020, long after the MU69 flyby, when all of the data from that flyby have reached Earth. But before we put New Horizons into hibernation this month, we have some important work ahead. We'll observe five more KBOs with the onboard LORRI telescope/imager to learn about their surface properties, satellite systems and rotation periods. This work is part of a larger set of observations of 25-35 Kuiper Belt objects from 2016 to 2020 on this extended mission. Learning about these KBOs from close range and at angles that we cannot observe from Earth makes will give us key context for the more detailed studies we'll make of MU69 from a thousand times closer than we can study any other KBO. In addition to that LORRI imaging of these objects, we're continuing our nearly round-the-clock observations of the charged particle and dust environment of the Kuiper Belt-both before and while New Horizons hibernates.

Also right ahead is a 2.5-minute engine burn planned for Dec. 9 (yes, a Saturday). This maneuver will both refine our course and optimize our flyby arrival time at MU69, by setting closest approach to 5:33 Universal Time (12:33 a.m. Eastern Standard Time) on Jan. 1, 2019.

Flying by at that time provides better visibility by the antennas of NASA's Deep Space Network, which will attempt to reflect radar waves off the surface of MU69 for New Horizons to receive. If it succeeds, that difficult experiment will help us determine the surface reflectivity and roughness of MU69 at radar wavelengths-something that has been successfully applied to study asteroids, comets, planetary satellites and even some planets, including Pluto, which New Horizons observed the same way in 2015.

Our Pluto observation set a record for the most distant object ever studied with radar -shattering the previous record by over 300 percent! If our radar experiment is successful on the much-smaller MU69 (which is perhaps 30 kilometers [19 miles] in diameter-tiny compared to Pluto's almost 2,400-kilometer [1,480-mile] diameter), then we'll break our own record, something unlikely to be surpassed for decades.

Since hibernating, New Horizons requires less attention from mission control than when we're in active operations. This will allow our mission team to focus fully on planning the detailed sequences that will tell New Horizons how to make every scientific observation of MU69 during its close-range pass in the days surrounding Jan. 1, 2019.

The year ahead will also include many observations of other KBOs, more study of the Sun's heliosphere with our dust and plasma instruments - SDC, PEPSSI, and SWAP, and our Alice ultraviolet spectrometer - as well as all the remaining flyby planning for MU69.

MU69 flyby operations will begin with distant navigation imaging to help us accurately home in on our target; that work will start in late August or September and will continue until literally 48 hours before flyby.

Our navigation teams at KinetX and NASA's Jet Propulsion Lab JPL will use those navigation images to compute the engine burns to further refine our course toward our planned closest approach point just 3,500 kilometers, or about 2,175 miles, from MU69. That's more than three times as close as we flew by Pluto, which should make for spectacular MU69 images and other data!

Additionally, beginning in the final weeks of 2018, we'll search for moons or dust structures around MU69 that could harm New Horizons if we were to collide with them during our 32,000-miles-per-hour flyby. If hazards that threaten the spacecraft are found, we can burn our engines to divert to a farther flyby, with a closest approach of 10,000 kilometers (about 6,200 miles), which should be safer.

Well, that's my update for now. For more mission news, stay tuned to NASA websites, our own project website, and our social media channels, which are listed below so you can bookmark them.

I'll write again early next year. Until then, I hope you have a safe and productive finish to 2017, a happy new year, and that you'll keep on exploring-just as we do!