2006年VOA标准英语-New US Mars Mission to Get Better Look at（在线收听）

By David McAlary
Washington
06 March 2006

The newest American mission to Mars is hurtling toward the red planet, due Friday to examine it in the sharpest detail yet. It will be the largest spacecraft to circle the planet, with big capabilities to match.

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Since 1997, the U.S. space agency NASA has been dispatching orbiters and companion landers to Mars about every two years to get a better geological understanding of Earth's nearest planetary neighbor. It especially wants to learn if conditions ever existed that could have supported life. The latest in the series is the huge Mars Reconnaissance Orbiter, two stories tall and nearly 15 meters wide. It is closing in on the red planet after a seven month voyage from Earth.

The head of NASA's Mars exploration program, Douglas McCuistion says the effort now moves into a more intensive phase of investigation.

"So this is a big mission for us," he said. "It's big in the strategic role in the Mars exploration program, it's the biggest orbiter sent to Mars in the past 30 years, carrying the most powerful suite of remote sensing instruments ever deployed to another planet."

Mars Reconnaissance Orbiter   
  
NASA says the Mars Reconnaissance Orbiter will have better capabilities for understanding the red planet's surface, subsurface, and atmosphere than the three American and European satellites now orbiting, the two U.S. robotic rovers on the ground, or any previous mission.

"It's a weather satellite, it's a geological surveyor, it's a pathfinder for future missions," said NASA project scientist Richard Zurek. He says the new orbiter, known by its English initials MRO, carries six instruments. Some are designed to seek clues to the water most planetary scientists believe once flowed on Mars and is a key to life. They can identify water-related minerals and penetrate the ground about one kilometer to seek layers of rock, ice, and water if it is present.

"MRO follows the 'Follow the Water' program by combining global monitoring of the atmosphere and surface, by taking regional surveys of interesting areas, and then zooming in with very high resolution observations of the surface of the planet," he said. "Together, these data sets provide a new window into Mars' history and they will provide the best sites for future landers to go and to explore with some confidence that they are safe sites."

The Mars Reconnaissance Orbiter will return torrents of data about the red planet, more than all other Mars missions combined. It has five times better resolution over more area than its predecessor satellites. It can see things as small as a kitchen table, thanks to super-sharp cameras and a planned altitude 20 percent lower than previous spacecraft - about 300 kilometers.

"Every time we have increased our ability to resolve detail on the planet, we see new things, and we expect new surprises," Zurek said. 
  

MRO pictured using its SHARAD radar to 'look' under surface of Mars  
  
With so much power to collect information, NASA had to give the new spacecraft the means to send huge amounts of it back to Earth, quickly. So the orbiter carries the largest antenna ever sent to Mars, three meters in diameter, and a transmitter powered by large solar panels. The space agency's manager for the project, James Graf, says the data flow will be 10 times per minute higher than previous Mars orbiters.

"These other missions have been producing fantastic data, but they have been bringing the data back through, essentially, a straw," he said. "What we are going to do is open the spigot and bring it back through a fire hose. That's crucial if you want to understand Mars. You want to increase the coverage and the resolution of your measurements, so you need that greater data."

Before the Mars Reconnaissance Orbiter can return any science, it must gradually adjust its extremely elongated 35-hour orbit to a circular two-hour one using atmospheric friction. This will take almost six months. Its primary data gathering phase is scheduled to last two years, but NASA says it is capable of going for up to a decade.