Comet-Hunting Probe to Launch on 10-Year Journey
Like the crew of the Pequod chasing Moby Dick, European and American scientists are preparing to embark on an epic journey to harpoon one of the solar system’s oldest and most mysterious entities -- a comet.
From a launching pad in French Guiana, the Rosetta mission is due to take off just before midnight tonight on a planned 10-year journey to intercept and land a probe on the comet Churyumov-Gerasimenko.
The European Space Agency craft will study the comet for about two years as it hurtles toward the sun.
“All systems are green,” project manager John Ellwood said from the launch site in Kourou, French Guiana. “This is going to be an amazing mission.”
The $1.3-billion Rosetta project is the first attempt to orbit and park on a comet. It is the largest and longest mission in the recent flurry of comet research.
Last month, NASA’s Stardust probe sailed through the tail of comet Wild-2 to collect a thumbnail-sized parcel of cosmic dust. Stardust is scheduled to return to Earth with its sample in 2006.
NASA plans to launch a mission in December called Deep Impact, which will attempt to throw a large copper projectile at comet Tempel 1 in July 2005 to reveal the interior of its nucleus.
Claudia Alexander, the U.S. project manager for Rosetta, said previous visits to comets were like looking at the White House from a car. With Rosetta, she said, “it’s like taking the White House tour and going inside and looking through all the rooms.”
Scientists are interested in comets because they contain matter from 4.6 billion years ago, when the solar system was formed. They are the leftover building blocks of the solar system, preserved in a deep freeze because they spend so much time in the dark outer reaches of space.
Many scientists believe that comets bombarding Earth may have arrived with complex organic molecules and “volatile” light elements that helped form the planet’s atmosphere and oceans, making the emergence of life possible.
“We have so many questions about the origins of the solar system and the origins of life and possibly life on other planets in our solar system,” Alexander said. “Comets might provide key clues to some of these questions.”
Because comets zip in from the far corners of the solar system, they also could provide a glimpse of what lies largely beyond humans’ current reach. “Beyond Saturn, we still have a lot of exploring to do,” she said.
The European Space Agency commissioned the Rosetta mission in 1993, naming it after the famous stone that helped decipher Egyptian hieroglyphics. More than a thousand people from around the world helped develop the orbiter and lander and their 21 scientific instruments.
The U.S. built three of the instruments and contributed to a fourth.
The devices will stay aboard the orbiting probe and help scientists figure out the composition of the comet’s nucleus, tail and atmosphere. Eleven of the scientists on the project are based at the Jet Propulsion Laboratory in Pasadena.
Rosetta and its lander, named Philae after the obelisk that helped decode the Rosetta stone, will be launched by an Ariane-5 rocket.
In January 2003, officials postponed the Rosetta launch because a version of the rocket veered off course and had to be destroyed. During the delay, Rosetta’s original target, a comet named Wirtanen, traveled out of range.
To reach its new target, Churyumov-Gerasimenko, Rosetta will have to swing several times around Earth to gather enough momentum to slingshot itself toward the comet.
Once past the asteroid belt between the orbits of Mars and Jupiter in 2011, the craft will go into “hibernation” as it drifts through the dark, chilly region beyond.
The craft will “wake up” in 2014 and attempt to match the orbit of Churyumov-Gerasimenko, traveling about 84,000 mph. Rosetta will meet the comet about 420 million miles away from the sun.
Eventually, Rosetta will inch to within miles of the comet’s 2 1/2-mile-wide nucleus to map the surface and look for a suitable place to drop the spidery Philae.
Philae will be sent down at a “walking speed” to the comet’s surface, which could be as soft as a fluffy snowball or as hard as ice. To avoid bouncing back into space, the 220-pound lander will absorb the shock with three specially designed legs, grip the surface with ice pitons and secure itself by firing a harpoon into the nucleus.
As the comet approaches the sun, the frozen gases that envelop it will evaporate, creating a long tail of dust.
The instruments aboard Philae and Rosetta will take close-up pictures of the nucleus, bore into the icy lump, and analyze the gases and plasma around it. The mission will continue until at least December 2015, after Churyumov-Gerasimenko has made its closest approach to the sun and begun to swing back into outer space.
Rosetta’s long journey to reach the comet will expose it to numerous hazards, including X-rays and charged particles that could damage the craft’s instruments and computer memory.
One of the biggest problems will be managing a project that could extend beyond the careers of some of its designers.
“Obviously we’ve had to look at how to keep the knowledge alive so we can operate them in 10 years’ time,” Ellwood said. “It’s almost like transferring information from father to son at the universities and institutes.”
Still, he remains optimistic about the mission’s success, despite the ESA’s bad luck with the Beagle 2 probe, which apparently failed as it attempted to land on Mars late last year.
“Everyone has their heart in their mouth a bit,” he said. “I’m sure we’ve really looked at everything on the space vehicle, but I can’t help being a bit nervous.”
