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April 28, 2017

The PI's Perspective: No Sleeping Back on Earth!

Did this get your attention? It sure got mine! This provocative image of a scale model of Pluto "hanging" over a harbor was produced by the Griffith Observatory in Los Angeles and CuriosityStream.

Three weeks ago we put our New Horizons spacecraft into hibernation mode, the first time we'd done that since late 2014, before the Pluto flyby. By coincidence, that same day – April 7—was also the exact halfway mark on the calendar between our Pluto and Kuiper Belt object (KBO) flybys!

The hibernation period we're in will last through mid-September. Every Monday between now and then, the spacecraft will check in with a health report, in which it sends one of seven possible "beacon tones" ranging from what we call "green" (meaning all's well) to various shades of "red" (which mean something is amiss). On the way to Pluto we hibernated for a total of about 250 weeks during 2007-2014, and only saw a handful of red beacons over all those weeks. And so far in this hibernation, on all three Mondays, New Horizons has sent green beacons.

Science team members at the Southwest Research Institute in Boulder, Colorado, discuss MU69 flyby plans during a telecon with counterparts at the Johns Hopkins Applied Physics Lab in Laurel, Maryland. (Credit: Alan Stern)

We've used spacecraft hibernation a lot since 2008. This mode turns off most onboard systems, but leaves the radios, main computer, power distribution and thermal control systems active. Our three space environment monitoring scientific instruments—SWAP, PEPSSI and SDC – also continue to operate. By turning off other electronics (like those for guidance and propulsion, and all backup systems) we save on time and, therefore, wear and tear on many spacecraft components, prolonging their life.

The other big advantage of hibernation is that our mission and science operations teams get a break from babysitting the bird and can concentrate on other things—in this case, detailed planning for that KBO flyby coming on Jan. 1, 2019. So while our spacecraft may be dozing, our team sure isn't—they are as busy as can be with the many hundreds of flyby planning details that have to be completed this year, so we can finish testing the plan early next year during another hibernation. After all, flyby operations begin in July 2018, which is less than 15 months away!

Before we went into hibernation mode earlier this month, New Horizons finished downlinking all the data it took on distant KBOs in January. It also sent back the data we collected from January through March on Kuiper Belt dust distribution and the charged-particle radiation environment a half-billion miles past Pluto. Our science team is now analyzing these data, and we're already finding some interesting results — including a wide range of dwarf planet surface properties. More on that in another PI Perspective...

Meanwhile, as New Horizons hibernates, the three scientific instruments I mentioned earlier will gather more data on the radiation and dust environment of the Kuiper Belt, something we can do much better than the Voyagers did in the 1990s. The reason why we can do so much better is simply that we have the first detector ever to fly in the Kuiper Belt and our radiation instruments were built in the 2000s, and are therefore highly advanced compared to their cousins on the venerable Voyagers that were built in the 1970s.

Our pathway to MU69: This diagram depicts our path across 5 billion miles of space to reach Pluto and then fly by MU69 on the first day of 2019. The position of Pluto is not where it was when we flew past in 2015, but where it will be on MU69 flyby day, a billion miles sunward of MU69. (Credits: NASA/JHUAPL/SwRI)

In addition to planning the command sequences that will choreograph all seven of our scientific instruments and the relevant spacecraft operations during our KBO flyby, there are some other important, mission related events this summer:

Beginning May 1 and continuing across the summer, NASA's Hubble Space Telescope will take images of our flyby KBO against star fields. We'll use these images to refine our knowledge of the target's orbit so we can assess the need for any engine burns – course corrections – as we home in. The next such burn opportunity is in early December.

In June, our science team will hold a major workshop to evaluate the trades (pros and cons) involved in choosing the best altitude for the flyby. Our goal is to get the best science with the highest probability of mission success, and a lot of factors are involved. Choosing that distance is more complex than just "go as close as we can," since some objectives are better served with the spacecraft farther out, or at a more leisurely pace a more distant flyby that can fit more observations in while we're very close to the target. The ultimate flyby distance will be somewhere between about 3,000 and 20,000 kilometers (1,875 to 12,500 miles). We'll let you know later this summer what altitude came out on top.

On June 3, and then again on July 10 and 17, our flyby KBO—called 2014 MU69—will occult (block the light) from a different star on each date. No such "stellar occultation" of MU69 has ever been observed, so we're pretty excited. If we're successful in deploying telescopes to the occultation paths in South America and Africa and getting the goods, we will learn about MU69's size, if it has rings or other hazardous debris in orbit around it, and maybe even something about its shape. All of that will help feed our flyby planning effort.

NASA's Hubble Space Telescope will be pressed into service for us again in June and July – this time to measure how fast MU69 rotates and how strongly its brightness varies as it turns on its axis. Because MU69 is so faint, not even the world's largest groundbased telescopes can make this measurement. But Hubble can, and we'll use this information to better plan the exact timing and other details of the close flyby activities on Jan. 1, 2019.

I was pleased to give retired planetary scientist Mike Belton, pictured here with his wife, Anna, this Pluto globe earlier this year. Mike chaired the 2003 National Academy planetary decadal report that placed the exploration of Pluto at the top of NASA's new planetary mission priority list. Mike and his decadal survey committee of experts are unsung heroes of the exploration of Pluto! Credit: Tod Lauer)

What I've just summarized, along with more Pluto science analysis of the Pluto system datasets we collected and just finished transmitting to the ground last October, will fill the next few months for the New Horizons project team. (In fact, two-dozen new Pluto system research papers are being published in the May 1 issue of the planetary science journal Icarus.)

One last thing I want to tell you is something I get asked a lot about. Yes, we're going to give 2014 MU69 a real name, rather than just the "license plate" designator it has now. The details of how we'll name it are still being worked out, but NASA announced a few weeks back that it will involve a public naming contest, as we requested. Look for more information on that in the fall.

For news in the meantime, stay tuned to our websites and our social media channels. I'll write again in the summer.

Until then, I hope you'll keep on exploring—just as we do!

–Alan Stern