After several weeks of sensitive searches for rings, small moons and other potential hazards around 2014 MU69, a Kuiper belt object nicknamed Ultima Thule, the dozen-member New Horizons hazard watch team gave the ‘all clear’ for the spacecraft to remain on a path that takes it about 2,200 miles (3,500 km) from Ultima Thule, instead of a hazard-avoiding detour that would have pushed it three times farther out.
An artist’s impression of New Horizons encountering Ultima Thule. Image credit: NASA / Johns Hopkins Applied Physics Laboratory / Southwest Research Institute / Alex Parker.
“New Horizons is now targeted for the optimal flyby, over three times closer than we flew to Pluto. Ultima, here we come,” said New Horizons principal investigator Dr. Alan Stern, a researcher at Southwest Research Institute.
New Horizons will make its historic close approach to Ultima Thule at 12:33 a.m. EST on January 1, 2019.
With the probe blazing though space at some 31,500 mph (50,700 km per hour), a particle as small as a grain of rice could be lethal to the piano-sized probe.
The New Horizons hazard watch team had been using the spacecraft’s most powerful telescopic camera, the Long Range Reconnaissance Imager (LORRI), to look for potential hazards.
The decision on whether to keep the probe on its original course or divert to a more distant flyby, which would have produced less-detailed data, had to be made this week since the last opportunity to maneuver the spacecraft onto another trajectory was yesterday, December 18, 2018.
This image of Ultima Thule (bright yellow spot in the middle) was made by combining hundreds images taken between August and mid-December by New Horizons’ Long Range Reconnaissance Imager (LORRI). The image has been colored using deep blue for the darkest regions and yellow for the brightest. The two possible flyby distances for New Horizons are indicated by the two concentric circles. The mission has decided to fly along the closer path, toward the target point marked by an X. Individual images contain many background stars, but by combining images taken at different distances from Ultima Thule, most of the stars can be identified and removed. However, some of them leave behind traces, which can be seen as faint circles radiating away from the target point. Image credit: NASA / Johns Hopkins Applied Physics Laboratory / Southwest Research Institute.
Any ring structure reflecting even just five 10-millionths of the sunlight falling on it would have been visible in the images, as would any moons more than about 2 miles (3 km) across, but the team members saw none.
They will continue to look for rings or moons that are very close to Ultima Thule, but those would not pose a risk.
“Our team feels like we have been riding along with the spacecraft, as if we were mariners perched on the crow’s nest of a ship, looking out for dangers ahead,” said hazards team lead Dr. Mark Showalter, of the SETI Institute.
“We were in complete consensus that the spacecraft should remain on the closer trajectory, and mission leadership adopted our recommendation.”
