Engine burn puts New Horizons on track to Ultima Thule
The engine burn, which sped up the spacecraft by 4.6 miles per hour (2.1 meters per second), was the first to use actual optical navigation photos of Ultima Thule taken with New Horizons‘ Long Range Reconnaissance Imager (LORRI).
To complete the most distant course correction ever conducted by a spacecraft, mission scientists used the LORRI data to determine the probe’s position relative to its second target and calculate the level of maneuvering required to hit its flyby aim point, just 2,200 miles (3,500 km) at closest approach. If everything takes place as it is currently envisioned, that will be on January 1, 2019, at 12:33 a.m. EST (04:33 GMT).
“Thanks to this maneuver, we’re right down the middle of the pike and on time for the farthest exploration of worlds in history–more than a billion miles beyond Pluto,” said mission principal investigator Alan Stern of the Southwest Research Institute (SwRI) located in Boulder, Colorado.
Currently, the spacecraft is about 3.95 billion miles (6.35 billion km) from Earth and speeding toward its second target at a rate of about 32,256 miles (51,911 km) per hour.
“The recent navigations have helped us confirm that Ultima is within about 300 miles (500 km) of its expected position, which is exceptionally good. We’re excited for the flyby,” stated New Horizons navigation team chief Fred Pelletier of KinetX Aerospace, Inc.
From a distance of four billion miles, the mission team will need to direct the spacecraft into a 75 by 200 mile (120 by 320 km) “box” for closest approach and predict the flyby timing to within 140 seconds.
“Since we are flying very fast and close to the surface of Ultima, approximately four times closer than the Pluto flyby in July 2015, the timing of the flyby must be very accurate. The images help to determine the position and timing of the flyby, but we must also trust the prior estimate of Ultima’s position and velocity to ensure a successful flyby. These first images give us confidence that Ultima is where we expected it to be, and the timing of the flyby will be accurate,” explained New Horizons optical navigation lead Derek Nelson, also of KinetX Aerospace, Inc.
Ultima Thule was discovered with the use of Hubble Space Telescope (HST) in 2014. The HST was needed because ground-based telescopes failed to find a second target for the New Horizons spacecraft after it had left the vicinity of Pluto. Three times in 2017 and once in 2018, mission scientists took advantage of the KBO occulting or passing in front of a star to hone in on its location and obtain data that assisted the team in refining flyby plans.
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.