NASA craft 'healthy and ready' for comet collision

[Guest Glenn]

Source: Reuters

 

July 04, 2005

 

PASADENA, California: A NASA spacecraft is "healthy and ready" for its collision with a comet and has already provided images critical to understanding the building blocks of life on Earth, officials said.

 

While still roughly 2.4 million kilometres from its target, the fast-moving Deep Impact craft is on track for its release today of a coffee-table sized impactor that is expected to blast a stadium-sized crater into comet Tempel 1.

 

"Both the fly-by and the impactor spacecraft are healthy and ready for encounter operations," Deep Impact's mission manager, Dave Spencer, told reporters at NASA's Jet Propulsion Laboratory in Pasadena.

 

At 1.52am (15:52 AEST) on Monday, the 350kg copper-fortified impactor is expected to smash into the comet at 37,010km/h, a speed that would make the flight from New York to Los Angeles a mere 6 minutes.

 

Although all of the spacecraft's systems appear to be in working order, officials said there were contingency plans in place if the impactor failed to detach from the ship. One alternative includes sending both to collide with the comet.

 

Tempel 1, which JPL scientist Don Yeomans described as "a jet black, pickle-shaped, icy dirt ball the size of Washington DC," will be about 133 million kilometres away from Earth at the time of the crash.

 

The aim of the mission, the first to come in direct contact with a comet's nucleus, is to photograph material formed billions of years ago during the creation of the solar system.

 

"These materials have not seen the light of day for 4.6 billion years," said Jessica Sunshine, a scientist working on the mission. "That's what we're waiting to see."

 

Comets are made of gas, dust and ice from the solar system's farthest regions. They often show bursts of activity, during which their surfaces crack to create tails of dust.

 

Deep Impact has already recorded several such outbursts from Tempel 1. NASA scientists said the data has shown that small outbursts, which they called "sneezes", are more common than they had previously thought.

 

The biggest "sneeze" witnessed so far doubled the amount of water in the comet's coma, or atmosphere, they said. Scientists have long held the theory that comets first brought water to Earth by crashing into its surface.

 

The outbursts are not big enough to blow the mission off course, according to NASA, though Spencer said the impactor was in for "a bumpy ride" as it approached the comet. Using its automatic pilot, the impactor will have three opportunities to adjust its trajectory in the two hours leading up to the impact.

 

The main spacecraft will be about 500km away from the comet at the time of the crash and will have about 13 minutes after the blast to capture images and data before it weathers a blizzard of particles thrown out of the comet's nucleus.

 

There are cameras aboard both the impactor and the main craft, and the blast will be observed by the Hubble, Spitzer and Chandra space telescopes.