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After a long day celebrating the arrival of Nasa's New Horizons spacecraft at Pluto and wondering about its fate while it was out of radio contact, mission controllers finally received confirmation Tuesday night that the spacecraft had performed its scientific tasks.
On schedule, at 8:52:37 pm. Eastern time, a message from the spacecraft arrived at Mission Control here at the Johns Hopkins Applied Physics Laboratory.
"We are in lock with carrier," said Alice Bowman, the missions operations manager. "Stand by for telemetry."
And a few moments later, when she confirmed that data was coming down, cheers erupted on Tuesday for the second time.
By design, communications from New Horizons ended at 11:17 pm 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, 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.
It was like New Year's Eve.
"We're going to do our 10-9-8 thing, and you can get your flags out," S Alan Stern, the principal investigator for NASA's New Horizons mission to Pluto, told the people gathered for the occasion.
"We're going to go absolutely ape."
The day climaxed a decade and a half of dreams and effort. Launched in 2006, New Horizons had traveled nine and a half years and three billion miles for a close encounter that was largely completed within hours. And yet that quick reconnaissance of Pluto has transformed what had been a fuzzy dot since it was discovered 85 years ago into a richly textured world, providing insight into the beginnings of the solar system and raw material for new mysteries that astronomers will ponder for years.
At 7:50 am, the crowd, which included the children of Clyde Tombaugh, the astronomer who discovered Pluto in 1930, cheered - albeit 72 seconds late.
New Horizons had already begun speeding away from Pluto at 31,000 miles per hour. The latest calculations by the spacecraft navigators indicated that New Horizons would arrive at the closest approach 72 seconds ahead of schedule.
But the path of New Horizons was within the margins that the mission team had aimed for, and to avoid the risk of causing a problem with unnecessary tinkering, no updated commands to tweak the timing had been sent to the spacecraft.
"We were close enough," said Christopher B Hersman, the mission's systems engineer.
As everyone cheered, no one knew how the spacecraft, in the midst of 22 hours of automated science operations, was faring. And there was a chance, however small, that it was not faring well: A wayward piece of debris, for instance, could destroy the craft.
"We always talk about the spacecraft as being a child, maybe a teenager," Bowman said during a news conference after the flyby. "There was absolutely nothing anybody on the operations team could do, just to trust that we had prepared it well to set off on its journey on its own."
Nasa released the newest colour image of Pluto, which was sent down Monday and offers the clearest view yet of an icy world with a Mars-like reddish tint.
"You can see regions of various kinds of brightness," Stern said during the news conference. "Very dark regions near the Equator, very bright regions just to the north of that, broad intermediate zones over the pole. What we know is on the surface we see a history of impacts. We see a history of surface activity."
He said there appeared to be about five regions of distinct terrain, and even a prominent bright feature in the shape of a heart appeared to show clear differences.
In a version of the picture in which colors had been exaggerated to show various features, Pluto looked as if a preschooler had smeared finger paints all over it. "This is just a very psychedelic image," said Catherine Olkin, the deputy project scientist.
From telescope observations on Earth, astronomers have known for decades of a bright spot on this side of Pluto, and the New Horizons trajectory was chosen in part so it would see the spot in sunlight. As the spacecraft approached, the bright spot resolved into that heart shape.
In the image with the exaggerated colors, the right side of the heart is distinctly bluer than the pale yellowish left side, with a sharp boundary between the two.
Annette Tombaugh, Clyde Tombaugh's daughter, talked about what her father, who died in 1997, would have thought of the probe's Pluto revelations.
"He would have said, 'That's a pretty neat heart,' " Tombaugh said. "If he were here, he would be on the team learning along with everybody else."
The scientists also had a closer look at the dark splotches that circle Pluto's Equator.
Additional data from other instruments to identify some of the chemical makeup of the surface and map the range of temperatures will help the researchers figure out the nature of such features.
Because Pluto is the Roman god of the underworld, the scientists drew on underworld entities from myths and literature in beginning to assign informal names to the regions.
A large splotch that resembles a whale was named Cthulu, a deity from a H P Lovecraft story. Other splotch names included Meng-Po, the goddess of forgetfulness in Chinese mythology; Balrog, a creature in J R R Tolkien's "Lord of the Rings" books; and Vucub Came and Hun Came, death gods of Mayan mythology.
"We got tired of calling it the dark spot on the left and the dark spot on the right," said Jeffrey M. Moore, the leader of the geology, geophysics and imaging team.
By Wednesday, the spacecraft will be mostly finished with the data-collecting phase of the mission and will begin sending back a trove of data for scientists to ponder. In the morning, the first batch of data will arrive on Earth, including sharper images of Pluto - 10 times the resolution of the image released Tuesday.
At the end of Tuesday night's news conference, John Grunsfeld, the associate administrator for NASA's science directorate, pointed to a Twitter posting by President Obama on his phone: "Pluto just had its first visitor! Thanks @NASA - it's a great day for discovery and American leadership."
Dr. Grunsfeld then turned to Dr. Stern, Ms. Bowman and Glen Fountain, the project manager. "Get some well-deserved rest," Dr. Grunsfeld said, "until 5 o'clock tomorrow morning."
The room erupted with laughter and applause.
© 2015 The New York Times News Service
