Spaceflight Insider

Engine burn refines New Horizons’ journey to KBO 2014 MU69

New Horizons trajectory (2017-12-09)

The New Horizons spacecraft is about 300 million miles (483 million kilometers) from 2014 MU69 – the Kuiper Belt object it will encounter on Jan. 1, 2019. (Click for the updated current position.) Image Credit: NASA / JHU-APL / SwRI

To optimize the timing of New Horizons’ closest flyby of Kuiper Belt Object (KBO) 2014 MU69, mission engineers carried out the spacecraft’s last engine burn during the long “cruise” phase of its journey – between Pluto and its second target (MU69) – on Saturday, December 9, 2017.

The probe’s thrusters were fired for 152 seconds, or about two-and-a-half minutes, via timed commands uploaded to New Horizons’ computer.

An artist's concept of NASA’s New Horizons spacecraft flying by a possible binary 2014 MU69 on Jan. 1, 2019. Early observations of MU69 hint at the Kuiper Belt object being either a binary orbiting pair or a contact (stuck together) pair of nearly like-sized bodies with diameters near 20 and 18 kilometers (12 and 11 miles). Photo and Caption Credit: Carlos Hernandez

An artist’s concept of NASA’s New Horizons spacecraft flying by a possible binary 2014 MU69 on January 1, 2019. Early observations of MU69 hint at the Kuiper Belt object being either a binary orbiting pair or a pair of nearly like-sized bodies with diameters near 12 and 11 miles, or 20 and 18 kilometers. Photo & Caption Credit: Carlos Hernandez

Done to both refine the spacecraft’s course toward MU69 and to set an ideal arrival time, the engine burn adjusted New Horizons’ trajectory by about 151 centimeters per second (approximately 3.4 miles per hour).

The closest approach to the KBO should occur just over half an hour after the New Year is ushered in on the U.S. East Coast, at 12:33 a.m. EST (5:33 GMT) on January 1, 2019.

If no course correction is needed due to debris being found that could pose a potential threat to the spacecraft, New Horizons should fly within 2,175 miles (3,500 km) of MU69 at its closest approach.

As done during the Pluto flyby, data will be sent back to Earth via NASA’s Deep Space Network (DSN), the world’s largest and most sensitive telecommunications system, with facilities located in the U.S., Spain, and Australia.

Mission scientists set the timing of the flyby to occur when DSN facilities’ radio antennas can best reflect radar waves from MU69, in the hope this will allow scientists to accurately measure the KBO’s reflectivity and surface roughness.

The December 9 course correction is the furthest ever conducted for a spacecraft. That record will be broken in October 2018 when the approach phase will be initiated with another course-correction maneuver.

MU69 was discovered in 2014 by the Hubble Space Telescope in a search for a second flyby target after Pluto. Mission scientists are now using observation data captured with both Hubble and the European Space Agency’s (ESA) Gaia observatory used to refine the spacecraft’s course to the KBO.

Radio signals to and from the spacecraft, which is currently 3.8 billion miles (6.1 billion km) from Earth, now take five hours and 41 minutes each way at the speed of light.

Confirmation of the maneuver’s success was received around 1:00 p.m. EST (18:00 GMT) on December 9 at mission headquarters in the Johns Hopkins University Applied Physics Laboratory (JHUAPL) in Laurel, Maryland.

“We are now on course and getting more excited all the time; this flyby is now barely a year away!” emphasized Principal Investigator Alan Stern of the Southwest Research Institute (SwRI) in Boulder, Colorado.

On December 21, the spacecraft, which is traveling at 31,786 miles (51,156 km) per hour, or more than 750,000 miles (1.2 million km) per day, will be put into hibernation for nearly six months.

It will be awakened on June 4, 2018, to begin flyby preparations. Later, according to Yanping Guo, New Horizons mission design lead at APL, the next course-correction opportunity will be sometime in October 2018 when the spacecraft starts its MU69 approach phase.

A public campaign seeking nicknames for MU69 ended on December 6. The mission team will announce the winning selection in early January 2018.



Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.

Reader Comments

Can’t wait to see data from MU69. By the way, as reported on this site, Voyager 1 – distance 11.7 billion miles, just did a trajectory correction maneuver on Nov 29. As such, I am not sure that the statement of “furthest ever” course correction is accurate. See

Voyager was doing orientation maneuvers to keep the comm dish pointed towards Earth. Not quite the same as a trajectory correction (velocity change). Still, being able to give Voyager-1 commands at that distance, and being wholly successful is a remarkable feat in its own right.

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