2006年VOA标准英语-Biggest, Most Sensitive US Mars Spacecraft（在线收听）

By David McAlary
Washington
10 March 2006

Mars Reconnaissance Orbiter   
  
Another U.S. spacecraft has begun orbiting Mars to study the red planet in unprecedented detail. The Mars Reconnaissance Orbiter will continue the search for signs that water and possibly life could have existed on it.

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One third of all U.S. spacecraft sent to Mars since the 1960s have failed to enter orbit, but the Mars Reconnaissance Orbiter is not among them.

Mission controllers at the Jet Propulsion Laboratory in Pasadena, California cheered after the spacecraft emerged from a communications blackout behind the planet and signalled that Mars' gravity had captured it. To let this happen, the orbiter fired thruster enginers to slow its nearly 18,000 kilometer per hour speed by one-third.

"After a six-month cruise, we're finally there. It's a great feeling," said Douglas McCuistion, chief of the U.S. Mars exploration program. "I can't wait for the scientists in a few months to be able to take control of the orbiter and see what we find. They are going to be like a bunch of kids with a new microscope, I think, being able to look at things they haven't seen before and I just can't wait to hear all the 'Wows!' coming from the science community. It will be quite exciting."

The successful rendezvous with the red planet ended a journey the Mars Reconnaissance Orbiter began last August when it launched from Florida. The 500 million kilometer voyage was smoother than expected. Mission manager Rob Lock says the spacecraft kept to its planned route so closely that in the last two days, controllers were able to cancel a pair of standby jet thruster firings that would have corrected the course if needed. "In fact, we have not done a maneuver since November of last year. We canceled our last two correction maneuvers on our way to Mars because our trajectory has just been spot-on [perfect] for months now," he said.

The new spacecraft joins two other U.S. orbiters and one European satellite circling Mars. But it is much bigger and is designed to go into a lower orbit with the most powerful cameras and remote sensing instruments ever sent to a planet. It will beam back more information than all previous Mars missions combined at a rate 10 times faster the older craft.

Before it can return any science, though, it will take six-months to adjust its extremely elongated 35-hour long orbit to a circular one two-hours long using atmospheric friction.

"For the science teams right now, this is a period of waiting," said Richard Zurek, the chief mission scientist. He says when the Mars Reconnaissance Orbiter is finished correcting its path around the red planet, it will study the atmosphere, examine the surface for water-altered rocks in unprecedented detail, and even probe beneath the surface with radar. It will also scout for landing sites for future robot explorers and eventually human visitors.

"We're looking forward to when we will be able to open up and operate our instruments to their full capability," he said.