This is New Years Day and the big day for New Horizons' encounter with Arrokoth!

But it doesn't mean there was nice pictures of MU69 on the big LED displays in Time Square at 00:01 01-Jan-2019.

There are avoidable delays (press office closures due to government shut-downs) and unavoidable delays (speed of light), schedules (when is the flyby exactly?) and local buffering due to extremely slow data rates from a zillion miles away.

Roughly what time is it likely that some news or data will make it to the general public about any or all of the following:

  1. a flyby happened and New Horizons did or may not have survived it
  2. a photo or spectrum or some measurement of MU69 itself
  3. a deviation of some kind in the trajectory or velocity produced by gravitational deflection by MU69
  • 3
    $\begingroup$ Regarding to the shut down, gladly the mission is not affected: "NASA's public relations team will be absent. John Hopkins' Applied Physics Laboratory, which manages New Horizons for NASA, will still cover and publicize the flyby." - Casey Dreier, Dec 22, Happy Holidays. NASA is Shut Down. $\endgroup$
    – not_Prince
    Commented Dec 28, 2018 at 5:50
  • 2
    $\begingroup$ John Hopkins' Applied Physics Laboratory will be providing full coverage on their Youtube channel (this is unaffected by the mess in Washington) $\endgroup$ Commented Dec 28, 2018 at 6:11

2 Answers 2


According to this article, "The first images are expected by the evening of January 1, with release planned for January 2. More, higher resolution shots should follow." Evening is presumably that of Johns Hopkins University Applied Physics Laboratory, Eastern Standard Time (UTC-5). Other sources are a bit more specific:

Of particular interest on Tuesday 2019-01-01 (from the schedule below):

  • 0033 EST (0533 UTC) Closest approach
    It appears that data will be collected for about 3 hours after this time (note that it will take over 6 hours for any signal to reach Earth and that NH cannot collect and transmit data at the same time)
  • 0945-1015 EST (1445-1515 UTC) Live coverage of signal-acquisition
    It is at this time that we will know whether NH survived the encounter.
  • 1130-1230 EST (1630-1730 UTC) Press briefing: Spacecraft status, latest images and data download schedule
    All probe health data should have been received by this time and the status of the probe and its instruments should be known. Science data will follow with first imagery available possibly around 2000 EST (0100 Wednesday 2019-01-02 UTC).

A highly detailed schedule can be found here including:

  • 1045 EST (1545 UTC) End of system health data return (no science data)

  • 1835 EST (2335 UTC) End of first post-pass science data return
    "LORRI image at 300 meters per pixel -- hopefully a full globe image of about 100 pixels across" plus other science data. The initial LORRI image should be available shortly thereafter.

The JHUAPL is largely unaffected by the 3rd 2018 US government shutdown and will be providing full coverage on their Youtube channel and on the New Horizons website. There will also be live coverage on Twitter @JHUAPL

Keep in mind that we may not get anything close to the quality we got for the Pluto system. Given all the unknowns any images returned may end up being blurry (wrong slew rate) or blank (pointing in the wrong direction).

Schedule of events: Schedule of events Source: Alan Stern / JHUAPL via Twitter, screenshot of this page


In simple explanation, we won't able to know what's up with New Horizons right away. The probe will be busy collecting all the science data during the high-speed flyby.

Closest approach will be at a distance of 3,500 kilometers at about 05:33 on 1 January UTC, and it’ll happen at a zippy 14.16 kilometers per second. [1]

(empasis mine)

As happened at Pluto, New Horizons will not be communicating with Earth during closest approach, because it will be focused on gathering all the science it can during the high-speed flyby. Whenever it does turn back to point at Earth to transmit data it will take more than 6 hours for its data to traverse the distance between us. [1]

However, there will still be downlinks from New Horizons around its January 1 flyby available but don't expect it to be either good or punctual1:

Simulated images of expected imagery levels of detail Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA/Emily Lakdawalla from this page1

The downlinks from New Horizons around its 1 January 2019 flyby of 2014 MU69 will not contain its highest-resolution images. Instead, they will be photos that the team is reasonably confident will contain an image of 2014 MU69.1 Two "failsafe" downlinks are planned for before the closest approach, and three "New York Times" downlinks are planned over the two days after closest approach. These are Rosetta OSIRIS images of comet 67P/Churyumov-Gerasimenko, scaled to be approximately the same size that the New Horizons images of 67P are expected to be, with some processing to add blur and speckle noise (for a variety of reasons, New Horizons LORRI images of MU69 will not look as crisp as Rosetta OSIRIS images of 67P). They are at a phase angle of 10 degrees, similar to the 11-degree phase at which New Horizons will see MU69 from a distance.

One important caveat: the times reported above are when the images will be downlinked. This is not the same as when they will be published. New Horizons (unlike Curiosity, Opportunity, InSight, solar missions, and formerly Cassini) doesn't push images straight to the Web once they land on Earth. The mission will process them, and the team will write captions, and then NASA will have to vet the captions, and then NASA will publish the images at a time of day that'll maximize news coverage, all of which means it could be up to a day or so after downlink that these images get released.


1. A flyby happened and New Horizons did or may not have survived it

Currently, we are in the Approach phase, which began on 16 August and runs through 24 December (7 days before closest approach). During approach, New Horizons has been taking images for optical navigation and searching for potentially dust-generating hazards like rings or moons. (So far, it has not spotted any.) The in-situ instruments have been busy gathering data on the fields and particles in interplanetary space. [1]

Furthermore, the operations team weighed numerous factors in making its choice to closest approach. The considerations included what is known about MU69’s size, shape, and the likelihood of hazards near it, the challenges of navigating close to MU69 while obtaining sharp and well-exposed images, and other spacecraft resources and capabilities.2 It's unlikely that New Horizons will not survive the flyby.

2. A photo or spectrum or some measurement of MU69 itself

As said above, New Horizons has been snapping pictures of Ultima Thule to identify any potential hazards. The result so far is that it appears clear and safe to approach. Earliest downlinks will be available on January 1, the rest will released accordingly during the Departure phase that will last one week after the 2-day period around closest approach, from 3 through 8 January. After that, New Horizons will spend 20 months downlinking all the remaining data, until September 2020.

Regardless of U.S. government shutdown, the show will go on!

New Horizon flyby of Ultima Thule event timeline (from this page1):

New Horizon flyby of Ultima Thule event timeline
Source: Partial screenshot of this page1


1 Emily Lakdawalla, December 17, 2018, What to Expect When New Horizons Visits 2014 MU69, Ultima Thule (And When We Will Get Pictures), The Planetary Society.

2 Johns Hopkins University Applied Physics Laboratory (2017), 6 September 2017, New Horizons Files Flight Plan for 2019 Flyby.
Quoting New Horizons Principal Investigator Alan Stern of the Southwest Research Institute (SwRI), Boulder, Colorado.

Also of interest

  • $\begingroup$ One potential snag I see is NASA having to vet the images (or at least their captions) before release. With the current debacle who knows when NASA will be back up and running. Hopefully the folks at JHUAPL will come up with a work-around. $\endgroup$ Commented Dec 28, 2018 at 8:06
  • 2
    $\begingroup$ The shut down is a total mess, let's not talk about it. I have a definite failth on JHUAPL. I'll be there on time and cheer for them, as I did for JPL's InSight EDL back on Nov 26. $\endgroup$
    – not_Prince
    Commented Dec 28, 2018 at 8:20

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