To Ralph McNutt, of the Johns Hopkins Applied Physics Laboratory (APL), launch wasn't just a beginning - it was the culmination of a hard-fought, nearly two-decade-long battle in the scientific community to secure a mission to the ninth planet.

"When the announcer hit 'zero' and the Atlas V rocket began plowing its way through the wispy skin of this pale blue dot we call home, it was a special moment," says McNutt, principal investigator of the New Horizons Pluto Energetic Particle Spectrometer Science Investigation, or PEPSSI.

"We really were on the way, and no one could stop us from taking that path to new lands."

Science team co-investigator Richard Binzel of the Massachusetts Institute of Technology remembers the run-up to launch, a four-year concert of spacecraft design, build and testing, and mission planning that had to reach its crescendo by January 2006, in time to meet a month-long launch period and take advantage of an opportunity to use Jupiter's gravity as a slingshot toward deeper space.

"The transition from launch to flight is truly phenomenal," Binzel says.

"Before launch, the clock looms so large. Everything has to be ready at the launch window, or else! In cruise phase the pace of hard work continues, but now the responsibility feels different. We know New Horizons will reach Pluto!"

Asteroids and Jupiter
Helen Hart joined the mission operations team at APL in spring 2005, just as the team began launch simulations, planning for spacecraft and instrument checkouts, contingency simulations and launch-readiness reviews. Soon after liftoff they started checking out the spacecraft's subsystems and instruments.

Hart revels in the way the team "scrambled" to meet an early flight opportunity: passing 100,000 kilometers from asteroid 2002 JF56, later christened APL. "With that encounter came a chance to check out the special moving target guidance control that we wouldn't have a decent chance to use again until Pluto, but only if we scrambled," she says.

On June 13, 2006, the newly commissioned Ralph/Multispectral Visible Imaging Camera took a clear image of the small asteroid, proving that the control technique worked.

That same month, the New Horizons science team presented its ambitious plans for the 2007 Jupiter flyby and gravity assist. "We plunged into completing instrument checkout and planning for the Jupiter encounter," Hart recalls.

New Horizons made its closest approach to Jupiter on February 28, 2007 - a mere 13 months and two weeks after launch - not only getting a gravity assist that boosted its speed toward Pluto, but also stealing new looks at the solar system's largest planet and its four biggest moons.

Based on that success, mission leaders decided to start fully planning for the 2015 Pluto encounter.

"Most of us were expecting a bit of a respite after the Jupiter encounter, when we entered a long hibernation phase," says New Horizons Project Scientist Hal Weaver, of APL.

"But then we realized that it would be better to continue working on the planning for the Pluto encounter while the lessons learned from Jupiter are still fresh in our minds. So we've been keeping our noses to the grindstone for an extra two years to make sure we have the best possible flyby encounter at Pluto." Keeping Up the Pace

Mission principal investigator Alan Stern says he continuously marvels at New Horizons' growing distance - now more than 1.2 billion miles from the Sun and more than a billion miles from any other spacecraft, save for New Horizons' expended third-stage rocket, which is on its own course to the Kuiper Belt.

"Everything is working well - flight electronics, all seven scientific instruments, all the navigation sensors, all our thrusters, all our heaters, and the RTG [power source]. We aren't using any of our backup systems," he says.

"Equally good, we have lots of fuel in the tank, more than preflight predicts indicated we would likely have at this point."

He says more than 2,500 people worked on one aspect of New Horizons or another, from the launch vehicle and spacecraft, to the science instruments and RTG, to the ground systems, to navigation and Deep Space Network planning, to launch approval, budgeting and management.

"Although our flight and science team is not much more than 1 percent of that size now, NASA, the scientific community, and a lot of interested people around the world owe a giant thanks to all those who worked to design, build, test, and launch this beautiful bird toward its date with history in 2015," he says.

"Now it's our little team's job to safely shepherd her across another 2,000-plus days and another 1.8 billion miles so we can accomplish what a few of us set out to do, so long ago, in 1989."

By the end of this year, Weaver adds, an incredibly capable New Horizons spacecraft will be ready for a long hibernation phase and the mission team will be poised to tackle an ambitious Pluto encounter rehearsal during summer 2013.

"Even then, there are still a couple of years to wait before our dream of lifting the veil on Pluto is finally realized," He says. "Talk about delayed gratification! But, fortunately, the journey itself is fun and interesting."

On to the Frontier
The voyage through the vast emptiness of the outer solar system has made an impression on Binzel, a professor in MIT's Department of Earth, Atmospheric, and Planetary Sciences and a recognized expert on Pluto and the asteroids.

"Even if we had memorized the names and distances of the nine planets since childhood, the vastness of the outer solar system still remains impressive," he says.

"In three years we have crossed Saturn's orbit, but we still have six years to go. For the mission team, and all who follow along with us, we're experiencing the expanse of the solar system not just as distance, but as a significant measure of time on a human scale."

"Only four spacecraft have preceded us, and only the Voyagers are still sending postcards back from the edge of human grasp," McNutt says. "Pluto is the one planet that they missed in what has been, to date, the grandest tour of the solar system.

And their spacecraft is venturing into realms few have crossed before.

"History is hard to see when you are making it," he adds, "but that is what the New Horizons team has done and continues to do."