With just under two weeks remaining for its close flyby of the Pluto system on July 14, NASA’s New Horizons spacecraft has swung into full action in preparation for the historic event. As part of its pre-scheduled approach phase activities, the intrepid robotic explorer successfully conducted its final course correction maneuver, which put it right on top of the trajectory required for its upcoming close passage through the Pluto system.
This final course correction maneuver involved a 23-second burn of the spacecraft’s thrusters, which took place on 11:01 p.m. EDT on June 29 and was just the third for New Horizons following the beginning of its long-range reconnaissance of Pluto in January, after a 93-second burn on March 10 and another 45-second burn on June 14. The result of this latest highly accurate burn was to alter New Horizons’ velocity by a miniscule 27 centimeters per second, which might seem like an extremely small change, but will have a significant effect on the spacecraft’s trajectory nevertheless, without which New Horizons would have arrived 20 seconds late on Pluto and 184 km off target during the day of closest approach. “This maneuver was perfectly performed by the spacecraft and its operations team,” says Dr. Alan Stern, principal investigator for the New Horizons mission, at the Southwest Research Institute, in Boulder, Colo. “Now we’re set to fly right down the middle of the optimal approach corridor.”
Having successfully ticked off this latest milestone in its mission, the New Horizons spacecraft is continuing to gather science data and take images of Pluto and its assortage of moons with its onboard Long-Range Reconnaissance Imager, or LORRI, while getting closer to its ultimate destination by approximately 1.2 million km with each passing day. The difference a few weeks have made in the detail of the returned images is quite significant, with the dwarf planet having already being resolved into a fascinating world which exhibits an exciting and as-of-yet mysterious set of bright and dark surface features.
At the same time, Pluto’s biggest moon Charon has put on quite a show of its own, featuring an enigmatic and quite unexpected dark area on its north pole which forms antithesis to the northern bright spot that has already been identified on Pluto. “Most surprising result is Charon’s dark pole,” said Dr. Simon Porter, a postdoc for the New Horizons mission at the Southwest Research Institute, during a recent “Ask Me Anything” session on reddit. “Popped out in early images, thought it was a mistake at first. But better resolution images still show it. It’s the only part of Charon that seems different from the rest.”
“For me, Charon’s dark pole [was most surprising],” added Dr. Amanda Zangari, also a postdoctoral researcher for the New Horizons mission at the Southwest Research Institute. “We all think this is hysterical, because Charon had a dark pole in the simulation we did of what the encounter would be like. It was also a surprise because Charon’s rotational light curve (i.e. its pattern of light and dark) is very subtle, so while we knew Pluto was going to have dark spots, Charon very well could have been uniform.”
One of the most important activities that is currently ongoing for the mission’s science teams is the search for any new moonlets or dust debris around Pluto that could potentially pose a hazard for the spacecraft as it plunges through the Pluto system on July 14. The chances for such a debris hazard are fortunately getting ever smaller as time goes by, as evidenced by the analysis of thousands of 10-second exposures that were taken by LORRI during the mission’s approach phase to Pluto, which failed to reveal the presence of any threatening dust debris rings or moonlets thus far. In addition, the search for rings around the distant dwarf planet has also come up empty until now, but that could change during the next few weeks as New Horizons approaches ever closer to Pluto and especially after its departure from the distant planet. “We don’t know if Pluto does or does not have rings,” explains Zangari. “They’re possible, especially because of Pluto’s crazy outer moon system, and if there’s a source in the system that can actively supply them, like Enceladus does for the Saturn system. Also the centaur Chariklo has rings, and no one expected that. As part of the hazard search we looked for them, but the best time to see rings is in something called forward scattering. We [will] pass behind Pluto and see if we see any dust lit up by the Sun, kind of like how it’s hard to see when you drive into bright light because all the crap on your windshield gets lit up. This is how Jupiter’s rings were discovered by Voyager, and we have some observations that we will take as we leave the Pluto system that will look for them.”
More of these fascinating observations are nearly upon us, and it’s only a matter of a few more weeks before speculation and theory will be replaced by hard facts and high-definition images. Up till now, New Horizons, which is currently at a distance of 16 million km from Pluto and closing in fast, remains in perfect health, ready to open the gates of the Solar System’s planetary underworld for all to see. “We are really on the final path,” says Glen Fountain, project manager for the New Horizons mission, at the Johns Hopkins University Applied Physics Laboratory, in Laurel, Md. “It just gets better and more exciting every day.”
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