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March 23, 2021

The PI's Perspective: Far From Home

New Horizons remains healthy and continues to send valuable data from the Kuiper Belt, even as it speeds farther and farther from Earth and the Sun.

I'm going to focus this PI's Perspective on a major upcoming mission mile marker — namely, New Horizons being 50 astronomical units (AU) from the Sun next month. But first, some mission news.

The flight of NASA's New Horizons mission. (Credit: NASA/Johns Hopkins APL/Southwest Research Institute)

Our biggest news is that most of our latest flight software upgrades, which will provide new scientific capabilities on the spacecraft, are in final test and on track to be uplinked in July. In fact, one of those updates, for our solar wind instrument called SWAP, is already aboard the spacecraft — and being used to produce new science! That software, transmitted to New Horizons in mid-February and tested for a week at the end of February, allows us to see much finer structures in the solar wind as we plow toward the heliopause, the outer edge of the heliosphere that surrounds the solar system.

We're also preparing another search for Kuiper Belt objects (KBOs) to study as we pass by them; those same summertime searches will also look for a new flyby target KBO, just as we did in our 2020 searches. Keep in mind, the search for Arrokoth (2014 MU69) took four years—and this search will go on for years, too, because it's a needle in a haystack challenge to find flyby KBOs! But this time, we're applying a new tool—artificial intelligence. Using machine-learning software, mission co-investigator JJ Kavelaars and collaborating scientist Wes Patrick have sped up and made those searches far more productive. In fact, when they reran the 2020 search data through their new software tools, it not only worked 100 times faster, but it turned up dozens of new KBOs that human searchers had not found in the search images! We'll be taking advantage of this important new tool again later this year, and next year and after that as well.

And one last news item: We're wrapping up development on a flight plan and command load to study three KBOs in May, determining their surface properties, shapes, and more. These kinds of studies we're doing from within the Kuiper Belt can't be done from Earth or even orbiting telescopes, and New Horizons has now studied almost 30 KBOs this way. For some of those KBOs, we we're close enough to search for and find satellites around them at resolutions even the Hubble Space Telescope cannot match, providing an important new window into how KBOs formed. Additional KBO observations are planned in September and December.

Reaching Rare Space

I mentioned earlier our big upcoming milestone: New Horizons will cross the amazing 50 AU distance marker on April 17 or 18, depending on your time zone here on Earth.). At 50 AU, we'll be 50 times as far from the Sun as Earth is! That's a milestone that only four operating spacecraft — Pioneers 10 and 11, and Voyagers 1 and 2 — have reached before us. That's so far away, in fact — almost 5 billion miles (7.5 billion kilometers) — that the Sun itself is smaller in the sky there than Jupiter is from Earth!

Of course, the Pioneers (now out of power and derelict) and the Voyagers (both still operating) are much farther out than New Horizons. In fact, they are so much farther out that none of them are the nearest spacecraft to us. That spacecraft is Juno, orbiting Jupiter 10 times closer to the Sun than New Horizons is now! And note that in mid-April, we'll have a news release, with some very special images we've taken from our perch so far away in the Kuiper Belt, so keep an eye out for that!

Looking back at the flight of New Horizons from Earth to 50 AU almost seems like a dream. Most of us on the flight team have been a part of it all the way, and during that time our kids have grown up, our parents (and we ourselves!) have grown older, and the first exploration of Pluto and the first KBO has been accomplished!

Our main exploration targets: Pluto (2015) and the much smaller Arrokoth (2019), to scale. Other exploration targets included Pluto's five moons. (Credit: NASA/Johns Hopkins APL/Southwest Research Institute)

For several years, full-scale replicas of Voyager (left) and New Horizons hung from the ceiling of the National Air and Space Museum in Washington, DC. (Credit: Alan Stern)

Looking ahead, just like other NASA planetary missions in extended (post-prime mission) operations, every three years we have to propose a new mission and science plan to NASA. If we are approved, we are funded for the next three years; if not, the mission will be terminated. Our next proposal will be due in early 2022. If New Horizons continues to be funded, it'll fly on, exploring the outer Kuiper Belt and the Sun's outer heliosphere. That's something no other spacecraft can do: we're the only one in this region!

We hope to continue proposing and performing science for many years. By the late 2030s, though, New Horizons may be too low on power to operate. That's because of the half-life of our plutonium power supply, which produces 3.3 watts less every year, and 33 watts less every decade. By the time it can't produce enough power to run the main spacecraft systems, New Horizons will be at or near 100 AU from the Sun—twice as far out as we are now. But even once the spacecraft is derelict—either because it runs out of power or fuel, or for any other reason—it will continue to coast outward, into the galaxy at a speed of nearly 3 AU (about 300 million miles) per year. In fact, even when the day comes in a few billion years that the Sun goes red giant and engulfs Earth, New Horizons, like the Pioneers and Voyagers, will still be out there, outliving even its home planet!

While you ponder that sobering thought, I'll conclude this report. In the meantime, I hope you'll keep on exploring — just as we do!

–Alan Stern

There are many ways to follow New Horizons news and commentary on social media! You can find others by searching on the Web.