Cosmic whiz sure plays a mean pinball
By Richard Macey
SMH February 28, 2004

Working in a space-age town shaved from French Guiana's Amazon forest, Sydney-born engineer Warwick Holmes admits the tension is starting to bite.

Rosetta, the first mission to try to land a mechanical explorer on a comet, was to begin its 10-year, $1.6-billion voyage from the European Space Agency's Kourou spaceport, on the shores of the Atlantic, last night.

The Australian's job is to lead a team making sure Rosetta is ready. But a rocket glitch yesterday pushed the launch back until at least next week.

Rosetta was originally to have gone up in January last year, on an Ariane 5 rocket, to a comet called Wirtanen. But weeks earlier an Ariane 5 exploded - the fifth failure in 14 launches. With six days to go, Rosetta's mission was scrubbed.

There was no Plan B. While the Ariane 5 has since proved reliable, another 170 years would pass before Wirtanen and Earth would line up for another opportunity. Rosetta seemed destined to become an expensive museum piece.

"My first feeling when we were told of the cancelled launch attempt . . . was absolute stunned disbelief," Mr Holmes said.

"The feeling was even worse than if the launcher had exploded - at least we would have known we tried. Having the launch cancelled without even the chance to try was unbearable."

Rosetta was saved when engineers found a new target, an almost unknown comet called Churyumov-Gerasimenko. Discovered in 1969, the five-kilometre ice world orbits between Earth and Jupiter.

To reach it Rosetta must play a game of planetary pinball, using the gravity of Earth and Mars to slingshot itself on its way.

It will zoom by Earth three times, and Mars once, before reaching the comet on May 22, 2014. On November 14 that year it will drop a 100-kilogram lander, Philae, on to the surface.

Scientists believe comets are debris left over from the birth of the planets 4.6 billion years ago.

"They are basically the cake-mix of our solar system," Mr Holmes said. "We will be licking the cake-mix bowl of the solar system for the first time."

He appreciates how much money is riding on the mission's success. "Some normally calm colleagues are beginning to show signs of nervousness and stress."

Few experiences, he said, matched witnessing an Ariane 5 rocket "erupt out of the Amazon jungle. When the two solid boosters ignite, they emanate a blindingly bright flash which reflects off the trees . . . and momentarily causes the whole sky to light up with an eerie green glow.

"About 12 seconds later the acoustic shock wave hits you; the first time it's frightening, it shakes your whole body.

"You know the boom associated with a close lightning strike? The noise from the launch vehicle can only be described at a continuous version of that same deep low booming crackling sound, but it runs for several minutes.

"It's like the whole sky is being ripped open."