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New Horizons: Occultations in Preparation for MU69

Our spacecraft have never encountered an object as far from Earth as 2014 MU69, but New Horizons will change all that when it races past the Kuiper Belt object on New Year’s Day of 2019. This summer is an interesting part of the project because planners will use it to gather as much information as possible about what they’ll find at the target. We have three occultations to work with, one of them just past, and they are as tricky as it gets.

But before I get to the occultations, let me offer condolences to the family and many New Horizons friends of Lisa Hardaway, who died in January at age 50. Hardaway helped to develop the LEISA (Linear Etalon Imaging Spectral Array) spectrometer that brought us such spectacular results during the Pluto/Charon flyby. She was program manager at Ball Aerospace for the Ralph instrument that contains LEISA. Mission scientists used data from the instrument package to make geological, color and composition maps of Pluto and its moons. The mission team has now dedicated the spectrometer in her memory.

“Lisa played a critical role on several of Ball’s more significant scientific programs from New Horizons, Hubble and Orion, to the Boeing F/A 18 E/F fighter jet and other national defense projects,” said Rob Strain, president of Ball Aerospace in Boulder, Colorado. “She made a positive impact on the careers of many, and her contributions will continue to give back for years to come.”

Image: Aerospace engineer Lisa Hardaway with the New Horizons spacecraft and Pluto. Hardaway was program manager for the Ralph instrument, which captured the first close-up color images of Pluto. Credit: Ball Aerospace.

Tracking a Fleeting Shadow

The MU69 occultations should provide useful data as we learn more about the KBO encounter environment. The first event occurred on June 2-3, with observers in Argentina and South Africa — 54 telescope teams in all — trying to track the shadow of MU69, which had occulted a star. Alan Stern, principal investigator for New Horizons, explains the goal:

“A tremendous amount had to go right to correctly execute such a massive observation campaign, but it did. The main goal of these observations was to search for hazards; the secondary objective was to try to glimpse the occultation of MU69 itself, in order to learn its precise size. Scouring all the dozens of datasets for these two objectives is going to take us a few weeks.”

Predicting the narrow stripe of MU69’s shadow over the Earth called for data from the European Space Agency’s Gaia mission as well as the Hubble Space Telescope. Remember that it was only in 2014, after a determined search, that the Hubble instrument discovered the 45-kilometer object, which is only 1/10,000th the mass of Pluto, although ten times larger than the average comet. Just the kind of KBO we’d like to study, in other words, but one we’ve had to characterize quickly in preparation for the upcoming flyby.

Image: Four members of the South African observation team scan the sky while waiting for the start of the 2014 MU69 occultation, early on the morning of June 3, 2017. The target field is in the Milky Way, seen here from their observation site in the Karoo desert near Vosburg, South Africa. They used portable telescopes to observe the event, as MU69, a small Kuiper Belt object and the next flyby target of NASA’s New Horizons spacecraft, passed in front of a distant star. Credits: NASA/JHUAPL/SwRI/Henry Throop.

As the data from the recent occultation are analyzed, we can look forward to another on July 10 and a third on July 17. For the July 10 event, mission scientists will use the Stratospheric Observatory for Infrared Astronomy (SOFIA), a 2.5-meter airborne telescope mounted in a Boeing 747SP jet. SOFIA can work at 45,000 feet, well above intervening clouds and capable of providing better data than the army of small telescopes used in the June occultation.

For the July 17 occultation, two dozen 40-centimeter telescopes will be deployed to Patagonia, where observers hope to scan more deeply for any debris around MU69. The star being occulted will be the brightest of the three, offering the best prospect for such detections. To track all this, keep an eye on the New Horizons KBO Chasers page, but as we get close to the event check the project’s Facebook page and the Twitter hashtag #mu69occ.

As of this morning, we’re 689,472,210 km from MU69 with 553 days to go until flyby.

Image: Projected path of the 2014 MU69 occultation shadow, on July 10 (left) and July 17, 2017 (right). Credits: Larry Wasserman/Lowell Observatory.


Comments on this entry are closed.

  • James M Essig June 27, 2017, 11:29

    It is nice to know that we have a probe that is going to fly by an object so distant. This is the first of a kind event regarding Kuiper Belt objects in terms of the distances involved. So cool that it is going to occur on New Year’s Day, 2019.

  • Charlie June 27, 2017, 11:35

    What I read in this article, just HAD to force me to comment on the total content of the article. Before I had read any further, I had jokingly said to myself that the picture of the four guys in the article above, where scanning the skies to determine the occultation of the stars by this target body.
    You can imagine, then to my TOTAL surprise that when I read the caption below the photograph that that was what they were actually doing!! The reason for my total surprise was that the idea that you could use an earthbound telescope, especially one like they were using, which I assumed would be a small one (especially if you are standing in an open field) to make sophisticated observations of an object that is, what, maybe three and a half billion miles from Earth and is 45 miles wide?
    I would have imagined that SUPREMELY ACCURATE observations would require a telescope of the sophistication and magnitude of Hubble to determine precisely such things as debris fields, and for such matters as (presumably) navigation I objectives.

    Aside from all this rather surprising bit of information as to determining what may be debris fields around the object in question, does anyone know how possible targets were acquired for New Horizons after it had encountered Pluto? What I’m asking here is, was a scan made by the Hubble telescope in the general vicinity of the expected flightpath of New Horizons or was there a much broader search within a cone of what might be a possible course adjustment to the craft within its fuel margins? I’m sort of more interested in the flightpath dynamics behind how the decision was made to go where they finally decided to go.

    • ljk June 27, 2017, 14:59

      These posts may help answer your question:



      And this one is about NH and HST coordinating observations of various KBOs:


    • Dave Gault June 28, 2017, 2:59

      Hi Charlie et al,
      It’s common practise to observe asteroids (and the moon) occult stars. Members of the International Occultation Timing Association (IOTA) do it all the time (pun). For these events mentioned in the article, the target star is mag. 13-15, so you need a substantial telescope (14-16 inch) but sometimes we are lucky to have asteroids occult bright stars, requiring very small telescopes. I’ve observed 976-Benjamina occult a mag. 7 star and I was using 7×50 binoculars. I have two friends who have observed asteroids occult stars using no more than their naked eyes. Rather cool to measure the diameter of an asteroid with only your eyes (or a pair of binoculars). Dave.

      • Andrei June 28, 2017, 12:17

        Yes, no super telescope is needed.
        The neccesary equipment is a telescope or binoculars that get light enough to see the star no more needed.
        A steady sky is best for good seeing.
        The hard part is exact timing of the event.

        (45 kilometers, not USA miles.)

        • ljk June 29, 2017, 9:14

          Is it just me or why do these events always seem to be visible only from the Southern Hemisphere? Why does the Universe keep ignoring the northern half of our planet? Yes, yes, there is that total solar eclipse coming up in August that will cross the USA, but look at how many other such celestial happenings occur in the southern half, or if they go north they are extreme north.

          I’m telling ya, cosmic bias.

  • jonW June 28, 2017, 14:27

    Does anyone know: how wide is the shadow, and how long would a transit last? It’s really amazing that this tiny rock is detectable from here in the inner solar system, due to its passing in front of a very far away, very faint star.

    • Larry July 1, 2017, 17:12

      The width of the shadow is the diameter of the object, so roughly 45km. Ideally you’d have about 50 observers stretched out in a line perpendicular to the path, about 1km apart, about 50km long. Some observers will be outside the path and miss the occultation completely, and the distance between those observers gives you the maximum diameter of the object. For those observers who see the occultation, the times of disappearance and reappearance of the star will give the size and profile of the object along the path. Probably the occultation will last a few seconds for those in the center of the path. Once they plug the positions of the observers and their timings into the appropriate formulas, they get an accurate measure of the object’s position on the sky, its size and approximate shape. And if the object has a measurable atmosphere, the star will not disappear instantly but will quickly fade, so an examination of the light curve will reveal it. (That requires that someone take video of the star during the event.)

  • J. Jason Wentworth June 29, 2017, 6:06

    These days, fifty is an unusually early age at which to die–I am glad that the LEISA array in the Ralph instrument essentially carries Lisa Hardaway’s name (it’s odd yet appropriate how these things just “line up”) and that the New Horizons mission team dedicated the spectrometer in her memory. That makes two people (Dr. Clyde Tombaugh, some of whose ashes are onboard, is the other one) for whom the New Horizons spacecraft is a memorial, which will outlast the Sun and the Earth. Also:

    As Dave Gault wrote above, occultation timings are very simple, yet are important for determining the diameters of asteroids (and other celestial bodies). By having several observers spaced out along a baseline (usually running north-south) several miles long that is perpendicular to the direction of apparent motion of an object, its cross-sectional shape can be determined, and:

    I recall reading about one unusual case (Dave, perhaps you remember the details of this incident?) of an asteroid occultation timing event in which one observer–who was in about the middle of the baseline–recorded a much longer occultation of the star. When all of the observers’ computed asteroid shadow widths were mapped out, this one observer’s unusually wide shadow width observation indicated that the asteroid had a huge mountain-like feature on one side. While unusual, such a feature isn’t at all impossible on such a small, low-gravity body, and (if memory serves) all of the observers were located on the agreed-upon baseline and used the cesium atomic clock universal time radio station WWV (see: http://www.google.com/#q=WWV ) to time-synchronize all of their observations, as is usual in occultation timing observations.

    • ljk June 29, 2017, 10:08

      While relatively huge geological features on planetoids are hardly impossible with probably many planetoids – just look at Itokawa with those boulders seeming to hang off the side of that little world:


      Could that “mountain” be a moon instead? And thank you for sharing this information, I was unaware of this. I wonder what other interesting similar astronomical observations are out there but have been so poorly reported beyond certain circles?

      • J. Jason Wentworth June 30, 2017, 3:35

        You’re welcome, and thank you for posting those Hayabusa mission images–I had never seen those “hanging-on” boulder pictures before. If any of the boulders are at the ends of shallow “gouges” in the regolith (I didn’t see this), they might be satellites that slowly spiraled in to land on Itokawa due to its “lumpy” gravitational field (this is suspected to be the case for “bi-lobed” asteroids that may once have been binary asteroids orbiting about a common center of gravity between them), and:

        I suppose the asteroidal “mountain” seen by the occultation observers might have been a close–at least in terms of line-of-sight–satellite instead. Had more than one observer noted the “bulge,” its separate nature might have been detected (I think probable–if not confirmed–asteroidal moons have been detected by amateur astronomers using time-synchronized occultation observations along baselines).

  • ljk July 19, 2017, 23:21

    July 19, 2017

    NASA’s New Horizons Team Strikes Gold in Argentina

    A primitive solar system object that’s more than four billion miles (6.5 billion kilometers) away passed in front of a distant star as seen from Earth. Just before midnight Eastern Time Sunday (12:50 a.m. local time July 17), several telescopes deployed by the New Horizons team in a remote part of Argentina were in precisely the right place at the right time to catch its fleeting shadow — an event that’s known as an occultation.

    In a matter of seconds, NASA’s New Horizons team captured new data on its elusive target, an ancient Kuiper Belt object known as 2014 MU69. Weary but excited team members succeeded in detecting the spacecraft’s next destination, in what’s being called the most ambitious and challenging ground occultation observation campaign in history.

    “So far we have five confirmed occultations,” said Marc Buie of the Southwest Research Institute (SwRI) in Boulder, Colorado, holding up five fingers as New Horizons scientists pored over the exhilarating initial data. Buie led a team of more than 60 observers who battled high winds and cold to set up a “picket fence” of 24 mobile telescopes in a remote region of Chubut and Santa Cruz, Argentina.

    Their goal: to spot the shadow of the mysterious Kuiper Belt object (KBO) where New Horizons will fly by on New Year’s Day 2019 – to better understand its size, shape, orbit and the environment around it.

    Before these observations, only the Hubble Space Telescope successfully detected MU69, and even it had not been able to determine MU69’s size or shape.


  • ljk August 4, 2017, 9:24


    “People love exploration”: what New Horizons researchers learned from the Pluto flyby

    Jana Howden

    04 August 2017

    NASA scientists were in Australia this week to talk about the scientific and social results of sending a spaceship to Pluto.

    “A scientific wonderland” is how Alan Stern – principle investigator of NASA’s New Horizons mission – described the myriad of unexpected discoveries beamed back from the Pluto flyby in 2015.

    Having worked on the project for 26 years, Stern was in Melbourne, Australia, this week to discuss not only the scientific discoveries of the mission, but its social implications too.

    In addition, NASA research engineer Michael Vincent, who also played a critical role in the mission’s success, was there to detail the technicalities of the spacecraft itself.

    Both speakers emphasised the critical role played by the Canberra Deep Space Communication Complex, an Australian-based tracking station used as a vital point of communication between the space probe and Earth.

    Although the probe successfully reached its closest approach to Pluto in July 2015, the data collected was only fully transmitted to Earth in October 2016.

    The mission returned a whirlwind of unexpected findings. It uncovered the largest glacier in the solar system and spotted massive ice volcanoes. It beamed back unexpected data on Pluto’s moons, and revealed a planet as active as Earth or Mars, despite being at a temperature of nearly absolute zero.

    Yet the mission’s success extended beyond this. “We made more than just scientific discoveries,” Stern said; “we rediscovered how much people love exploration.”

    As the space probe continues its journey deeper into the outskirts of our Solar System – with Kuiper Belt object 2014 MU69 having been nominated as the next target for the mission’s close flyby – Stern ruminated on the future of space travel and its ability to unite the people of our planet.

    “More than two billion individuals came to our website in the two days surrounding the flyby,” Stern said. “If two billion people wanted to watch a robot fly by Pluto, imagine what it will be like when the first humans step on Mars. It’ll be the most unifying event anybody could ever put on.”

  • ljk August 4, 2017, 10:39
  • ljk August 24, 2017, 23:11


    ‘Golden Record 2.0′: New Horizons Probe Could Carry Digital-Age Message for Aliens

    By Mike Wall, Space.com Senior Writer | August 24, 2017 12:00 pm ET

    NASA’s New Horizons spacecraft could end up bearing a message for intelligent aliens, just as the agency’s venerable Voyager probes are doing.

    Both Voyager 1 and Voyager 2 famously carry copies of the “Golden Record,” which are loaded with photos, music, sounds and other data designed to teach any extraterrestrials who might encounter the probes about humanity and its home planet.

    Though such an alien encounter isn’t likely, it is possible; Voyager 1 popped into interstellar space in August 2012, and its twin will probably do the same in the next few years, mission team members have said.

    New Horizons’ ultimate fate also lies beyond the solar system, “and it’s leaving without a Golden Record, without a message,” said Jon Lomberg, the design director for the Voyagers’ Golden Record. (He worked closely with astronomer and science communicator Carl Sagan, who chaired the committee that decided what information the record would contain.) “That seems like a missed opportunity,” he said.

    Lomberg wants to change things, by giving New Horizons a “Golden Record 2.0” — a new, crowdsourced digital version called the One Earth Message, which would be beamed out to the spacecraft in 2020.

    On Aug. 20 — the 40th anniversary of Voyager 2’s liftoff — he and his team launched a 40-day Kickstarter campaign, which seeks $72,000 to develop and maintain a website that will manage the photos and other material people submit for possible inclusion in the One Earth Message. If all goes according to plan, online voting will determine which content will ultimately make up the message.

    New Horizons, which flew past Pluto in July 2015, is now zooming toward a Jan. 1, 2019, rendezvous with a small object called 2014 MU69. It may take a year or so for the probe to beam all of its data from this second flyby home to Earth, Lomberg said; only then will New Horizons be able to spare the computer memory necessary to accommodate the One Earth Message.

    “That gives us a good two years to first put the message together, which I estimate will take at least a year, and then another year to put it all together in software, test it and make sure it’s suitable for upload,” Lomberg said.

    The upload to New Horizons would not happen without official NASA approval. This approval might be easier to obtain if the team approaches the agency with a finished product rather than a nebulous concept, Lomberg said.

    “Forty years ago, when I worked with Carl on the Golden Record, he didn’t go to NASA and try to get them to approve some vague idea of the message’s music and sounds,” Lomberg said. “He made it, and then he showed it to them and said what we did. They reacted to it. And if there was something they didn’t like — and there was one picture they didn’t like — they took it out.”

    Lomberg’s vision for the One Earth Message doesn’t end with New Horizons. Eventually, he would like every probe that leaves Earth to carry the message, or something like it.

    “I think our spacecraft are our finest technical masterpieces,” he said. “They’re essentially works of art, and every work of art should be signed.”

    “Signing” probes in this fashion is worth the effort, even if they drift alone through space for eternity, Lomberg added.

    “We will never know if there is an E.T. audience, but for the human audience that participates, it can be a profoundly moving experience to seriously contemplate communicating with the cosmos,” he said in a statement.

    You can learn more about the One Earth Message and its Kickstarter campaign here: https://www.kickstarter.com/projects/31060842/one-earth-message-a-digital-voyager-golden-record/description

  • ljk September 19, 2017, 12:55

    Wakened from its latest hibernation, New Horizons may visit additional KBOs


    To quote:

    Fuel saved during the MU69 encounter could be used to send New Horizons to a third KBO, a move that would require yet another mission extension. In 2016, NASA approved an extended mission for the MU69 flyby through the year 2021.

    On Sept. 6, Stern told members of NASA’s Outer Planets Assessment Group that mission scientists are already searching for an additional KBO target.

    “We have a fighting chance of having a second [Kuiper Belt Object] flyby,” Stern said.

    Approval of another mission extension will also provide more opportunities for New Horizons to continue its distant observations of KBOs, dwarf planets, and centaurs. Stern said that he intends to request a second extension once the MU69 flyby is completed and the data collected from it returned to Earth.

    Even that might not be the mission’s end. Stern foresees additional extensions beyond the one that would take it to a second KBO.

    “There’s fuel and power on board the spacecraft to operate it for another 20 years,” Stern said. “That’s not going to be a concern even for a third or fourth extended mission.”

    The probe will be put into another hibernation period on Dec. 22, 2017, during which it will remain until June 4, 2018, when it will be woken up in preparation for the MU69 encounter, which will officially begin in August 2018.