By design, communications from New Horizons ended at 11:17 p.m. the night before, and as planned, the craft remained out of contact for almost 22 hours as it took pictures and collected bountiful other measurements of Pluto and its five moons. The design of the spacecraft did not allow it to perform its observations while communicating with Earth, and the mission team wanted to squeeze in as much work as possible as New Horizons flew within 7,800 miles of the former ninth planet.

At a news conference a half an hour later, Ms. Bowman said that everything appeared to have gone smoothly. “We didn’t have any autonomy rule firings,” she said, referring to actions the spacecraft takes when something goes wrong. “And what that means, in layman terms, is that the spacecraft was happy.”

The first round of cheers came Tuesday morning, as a countdown clock for the closest Pluto approach, as calculated by mission scientists, ticked down to zero.