For key scientists, Pluto probe spans eras on Earth
Michael E. Ruane
The Washington Post News Service
July 13, 2015 (c) 2015, The Washington Post.
WASHINGTON — While NASA's New Horizons spacecraft has been racing across the solar system toward Pluto, back on Earth, mission scientist Andy Cheng has been waiting.
He has waited as his children grew up, moved out, and one got married, as his father and a younger brother died. He was patient as more than nine years passed.
Cheng was 50 when NASA got initial funding for the mission in 2001. He was 54 when the spacecraft was launched in 2006. He was 55 when it tore past Jupiter in 2007.
He is 63 now, and 3 billion miles, 3,450 days and several life events since launch, his wait is just about over.
At 7:49 a.m Tuesday, the spacecraft is scheduled for its close-up with Pluto, climaxing an endeavor that took up a large chunk of Earth time for Cheng and others while the probe crossed the vastness of space.
"A big fraction of your whole life is what one of these missions takes," he said last Thursday in Laurel, Maryland, in a classroom at the Johns Hopkins Applied Physics Laboratory, where he works and where the spacecraft was built.
"You just have to teach yourself: Wait. Just wait. Be patient. It's a very long time."
Cheng, of Potomac, Maryland, is the principal investigator for New Horizons' celebrated Long Range Reconnaissance Imager, called LORRI, which has been sending back ever clearer and more dramatic photos of Pluto.
Cheng led the team that designed it. And as the spacecraft streaks past the dwarf planet Tuesday, he said LORRI is "going to get the best pictures, the highest-resolution pictures."
The imager is part digital camera and part long-range telescope. It does not get blinded by glare, and is built of brittle silicon carbide, a gray crystal designed to withstand the extreme temperature differences of space travel, he said.
It's a superb device — the size of a big metal coffee urn — and was a late addition to the spacecraft, which already had six instruments.
It "went beyond the requirements for the mission," Cheng said. "It's a better telescope than . . . NASA . . . asked for. We said, 'We think we can put it in. We think we can do it within the cost and the schedule.' "
On Jan. 19, 2006, he attended the launch of New Horizons at Cape Canaveral, Florida.
"Launches are always nerve-racking," he said. "It gets very tense. The rocket goes up and you know that's the most dangerous time. . . . There are so many things that can go wrong, and any one of them can end your mission."
He knows that from personal experience.
He was part of the team that worked on NASA's CONTOUR mission, which was launched in 2002 to study comets. Two weeks later, as the spacecraft was preparing to leave Earth orbit, it blew up.
"Pieces were seen afterwards," he said. "Terrible disappointment."
New Horizons has already had one scary glitch, on July 4, when it inexplicably went dark for an hour and 16 minutes.
The spacecraft's main computer had become overloaded, and the spacecraft went into safe mode. It took three days for the New Horizons team to restore the spacecraft to normal operations. Cheng said if that happened again, during the flyby, "the whole encounter is gone."
"It can still go south," he said. "We could still lose it all."
But the launch was flawless.
Critical pieces of the mission, though, were still to come.
A big milestone was the spacecraft's visit to Jupiter in winter 2007.
Jupiter's gravity was used to grab the spacecraft and fling it toward Pluto at accelerated speed, like a baseball hit by a bat, he said. The Jupiter encounter sped New Horizons so much that it cut almost four years off the journey, Cheng said.
Back on Earth, the next year brought a sad milestone. Cheng's brother, Thomas, a popular cardiologist and university professor in Minneapolis, died Feb, 25, 2008, of multiple myeloma at the age of 55.
Two years later, Andy Cheng's daughter, Caroline, got married, and in 2011 his father, Sin-I Cheng, 89, died. The elder Cheng had been a professor of mechanical and aerospace engineering at Princeton University and an early expert in rocketry.
Meanwhile, New Horizons was headed beyond Jupiter to the orbits of Saturn, Uranus and Neptune.
The distances are so huge that it took the spacecraft about seven years to get from Jupiter to the orbit of Neptune on Aug. 25, 2014 — the last major point before Pluto — traveling at about 32,000 mph.
That period of the mission "was a whole lot of nothing," Cheng said. "There's just empty space. After Jupiter, there's a very long cruise to get to Pluto."
The spacecraft had been in periodic hibernation during the long trip. But Cheng had been busy. He helped plan other missions, including one called AIDA, designed to test a method of deflecting an asteroid by slamming a probe into it.
And when two more moons were found orbiting Pluto in 2011 and 2012, he helped in the effort to search for other potential "hazards" along the spacecraft's path.
"Are there other moons that we don't know about?" Cheng said. "Are there rings that we don't know about? We may have to fly through them. We don't actually want to hit anything."
Pluto has five known moons. LORRI and other imagers were used to scan for further trouble. The path looked clear.
Cheng was also involved in planning New Horizons's life after Pluto, and choosing the objects beyond the dwarf plant that the spacecraft could visit. "We have two candidates," he said. "We can only do one."
"If the spacecraft is still healthy, and we had a great Pluto encounter," he said, "then, yes, we'll be asking NASA to approve an extended mission." That visit could occur in 2019, he said.
At the start of this year, his attention refocused on Pluto.
It was now nine years since launch. Cheng's hair had thinned, and he had developed cataracts, he said.
But the payoff was coming. LORRI's pictures gradually became better and better as the distance closed.
"If you can imagine . . . Christmas, but you don't get all your presents at once, you get them in installments, spread out," he said. "That's what's going on. Every day you get a little more of your Christmas present."
And the wait?
"For me, it was worth it, for sure," he said. "It might be that I'm a fairly crazy kind of guy. So it might not be worth it to everyone."
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Video: Achenbach explains NASA's New Horizons mission. (By Tom LeGro/ The Washington Post)