The key to Rosetta's success ultimately depends on its power supply, two massive solar panels that stretch out 45 feet (14 meter) from each side of the orbiter. Project engineers specially designed the panels to operate at low temperatures and cull the most power from the low-intensity sunlight it will receive during its mission.

"I think we're setting a record for the farthest use of solar panels from the sun," Schwehm said. "[NASA's] Stardust used them from outside 2 AU, but we will reach out even farther."

Through much of the pre-rendezvous trip, Rosetta will be in a hibernation mode, generating only enough power keep its sensitive instruments from freezing in the cold of space. Mission controllers plan to awaken the spacecraft briefly in 2008 during its pass through the asteroid belt to study nearby space rocks, though definite targets won't be announced until later.

Despite its upcoming launch, Rosetta has certainly had its share of mission headaches.

The spacecraft's original flight plan called for a 2003 launch with a Comet Wirtanen in Rosetta's crosshairs. But ESA scrubbed that launch after an Ariane-5 rocket failed in December 2002.

The launch failure cast a pall over Rosetta scientists after their mission was put on indefinite delay, cutting their chances of a successful Wirtanen rendezvous. After some quick number crunching, mission planners settled on Churyumov-Gerasimenko, one of a number of original targets they had to choose from, as a viable alternative target.

"Last year we were pretty glum knowing that we were facing launch delay," Alexander told SPACE.com. "But now we're really there and I'm really looking forward to the extended mission. The years in between are going to go by fast."

The comet target switcheroo, however, was not without cost. To get to Churyumov-Gerasimenko, Rosetta has to swing by Earth not once but three times, starting in 2005 with subsequent passes every two years after. A Mars flyby in 2007 is also required to fling the spacecraft through the asteroid belt.

"The first step is to get into orbit and have an excellently working spacecraft," Schwehm said. "But even if it takes 10 years, [the science] is worth waiting for. After such a long launch delay, our scientists deserve it."

Rosetta is ESA's second dedicated comet rendezvous. The first, Giotto, visited two of the icy space snowballs starting with a historic pass by the famed Comet Halley in 1986. Six years later Giotto made its second cometary rendezvous during a flyby of Comet Grigg-Skjellup.