'It was just like we practiced': New Horizon's flawless Pluto flyby

It's official: New Horizons has successfully made it through its close flyby of the Pluto system unscathed. 

"We have a healthy spacecraft, we have a healthy system, and we are outbound for Pluto," Alice Bowman, mission operations manager for New Horizons, said just before 6 p.m. Pacific time Tuesday as the first group of ones and zeroes arrived at Mission Control at the Johns Hopkins Applied Physics Laboratory in Laurel, Md. 

"It was just like we practiced," she said.

The mission team had waited a long time for this moment.

"It's been 9 1/2 years, but this is the payday," said Hal Weaver, New Horizons project scientist. "We flew 7,500 miles above the surface of Pluto, 3 billion miles from home."

New Horizons' long journey to Pluto culminated in an instant Tuesday morning, when the NASA spacecraft went screaming past the dwarf planet at 30,800 mph -- but the mission is far from over.

Even as the spacecraft speeds deeper into the Kuiper belt, its instruments will continue to search for signs of faint rings around the small icy world and take measurements of the dust and plasma in Pluto's neighborhood.

And then there are all the new data that the craft has to send back to Earth.

New Horizons stopped communicating with ground control at 8:17 p.m. Pacific time Monday, and it did not resume contact until 5:52 p.m. Tuesday. 

Because the flyby window was so brief, mission architects wanted all of New Horizons' power to be focused on data collection rather than checking in with Earth.

The 22-hour absence of contact was nerve-racking for the mission scientists.

"There's nothing like a safe-mode event to sharpen one's senses," said John Grunsfeld, associate administrator for NASA's science mission directorate.

Bowman admitted that by Tuesday afternoon her anxiety was soaring.

"I did some more data checks once, twice, maybe a hundred times," she said.

The first batch of observations from the flyby will start to arrive on Earth at 2:32 a.m. Wednesday, and it will include the highest-resolution images taken by the spacecraft, when it was just 7,500 miles from Pluto's surface.

These black-and-white pictures will be 10 times more detailed than the best images we've seen so far.

"They will dazzle us," said Glenn Fountain, project manager on the mission. 

But it's not just to satisfy the public's curiosity that they are coming down first. 

"We know the world is excited to see them, but this is a safety issue," said Henry Throop, a scientist on the New Horizons team. "These are the images that we will get the most science from, and we want it to be the first to come down." 

The data will be received by one of three 70-meter antennas in NASA's Deep Space Network, but the information will be arriving at a slow trickle of just 1,000 to 4,000 bits per second.

That's about the speed of your old computer modem from 20 years ago, Throop said. He added that it would take 90 minutes for just one of these images to get fully downloaded.

New Horizons will continue to send the highest priority images in a compressed state for the next two weeks. Beginning in August it will start sending raw data back to Earth for eight hours a day. Mission scientists say it will take 16 months to get all the data downloaded.

"Scientifically, this will be the data set for Pluto that we will have for decades," Throop said. "We are not going back to Pluto anytime soon."

But even when New Horizons has nothing more to tell us about the dwarf planet and its immediate environment, its work may not be over.

New Horizons' principal investigator, Alan Stern, is hopeful that the spacecraft will journey to another object in the Kuiper belt -- one that is smaller than Pluto and closer in size to the comets that zip through our solar system.

The spacecraft is powered by plutonium, and it has enough left to keep it operational through the mid-2030s, Stern said.

Now that the flyby is over, the New Horizons team will work with NASA to choose among three potential Kuiper belt objects to send the spacecraft to next, and possibly fire its engines to point it in the right direction.

All three candidates are another billion miles beyond Pluto, and it would take New Horizons two or three years to reach one of them.

Even after a visit to a second object, the mission could still have legs.

"We could send it to a planetesimal" -- a much smaller object -- "and then have it explore the deep regions of the heliosphere," the immense magnetic bubble enveloping the solar system, Stern said. "It would be like Voyager, but with much more modern instruments."