NASA Mars Reconnaissance Orbiter Approaches Red Planet

三月 10, 2006

Washington, 09 Mar 2006

After a seven-month, 492-million-kilometer journey to Mars, NASA’s Mars Reconnaissance Orbiter (MRO) will begin the most critical minutes of its flight March 10, firing the main engines to slow the craft so Martian gravity can pull it into orbit around the Red Planet.

NASA’s latest Mars mission is putting a large, capable spacecraft into a low-altitude orbit around Mars for two years to search for evidence that water persisted on the surface of the planet for a long period of time, NASA officials announced March 8.

Other Mars missions have shown that water flowed across the surface at some point in Mars' history, but whether water was ever around long enough to offer a habitat for life is still a mystery.

"Once the spacecraft has successfully been placed in position,” said NASA's Mars Exploration Program Director Doug McCuistion, “this mission will greatly expand our scientific understanding of Mars, pave the way for future robotic missions later in this decade, and help us prepare for sending humans to Mars."


“We are clearly very excited about this potential of MRO doing science around Mars,” said Fuk Li, manager of NASA's Mars Exploration Program at a Jet Propulsion Laboratory briefing March 8, “but my heart rate is also going up for a different reason. The mission is entering into a very dangerous phase in the next several days.”

The initial capture by Martian gravity will put the orbiter into an elongated, 35-hour orbit. But the planned orbit for science observations is a low-altitude, nearly circular two-hour loop.

To get into the proper orbit to begin its mission, the orbiter will spend six months to seven months adjusting its orbit with an adventurous process called aerobraking.

"Aerobraking is like a high-wire act in open air," said MRO project manager Jim Graf at the NASA Jet Propulsion Laboratory in California.

The aerobraking technique will use hundreds of carefully calculated dips into the planet’s upper atmosphere â€" deep enough to slow the spacecraft by atmospheric drag but not deep enough to overheat the orbiter â€" to gain the desired orbit.

As the orbiter nears Mars March 10, ground controllers will wait for a signal that indicates the critical engine burn has begun to place it into low orbit. The burn will end after a suspenseful 30 minutes, with the orbiter behind Mars and out of radio contact.

The history of Mars exploration, Li said, shows that only a third of all spacecraft sent to the Red Planet actually have arrived and succeeded in their missions.

“For us,” Li added, “those are very sobering numbers and indicate to us how tough it is to get this mission operating correctly around Mars.”


The MRO spacecraft is physically larger than those designed for other missions, Graf said.

“It’s a much more capable spacecraft,” he added, “and has a lot more power ... because the payload itself is a large departure [from previous payloads], it’s the most technologically advanced payload ever sent to another planet.”

The orbiter carries six instruments that will produce data for studying Mars from underground layers to the top of the atmosphere:

• The most powerful telescopic camera ever sent to another planet, which will examine rocks the size of a small desk from its vantage point about 322 kilometers above the planet;

• An advanced mineral-mapper camera able to identify water-related deposits;

• A “context” camera with capabilities that complement the functions of the other two cameras;

• Radar to probe for buried ice and water;

• A weather camera to monitor the entire planet daily; and

• An infrared sounder to monitor atmospheric temperatures and the movement of water vapor.

"We're especially interested in water, whether it's ice, liquid or vapor," said Richard Zurek, Jet Propulsion Laboratory orbiter project scientist. "Learning more about where the water is today and where it was in the past will also guide future studies about whether Mars ever supported life."

The orbiter can transmit data to Earth at about 10 times the rate of any previous Mars mission. Scientists will analyze the information to gain a better understanding of changes in Martian atmosphere and the processes that formed and modified the planet's surface.

The MRO also will provide communications-relay support for future missions working on the surface of the planet.


When MRO arrives at Mars, it will join several other missions that already are studying the planet.

NASA’s Mars Global Surveyor, launched in 1996, had a primary mapping mission from 1999 to 2001, and today continues to gather data in a second extended mission. One of its most significant findings is evidence of possibly recent liquid water at the Mars surface.

NASA’s Mars Odyssey mission, another mapping mission launched in 2001, has provided strong evidence for large quantities of frozen water mixed into the top layer of soil in the 20 percent of the planet near its north and south poles.

NASA’s Mars rovers Spirit and Opportunity, launched in 2003 and still operating on the Martian surface, are mobile robotic field geologists sent to examine clues about the environmental history, particularly the history of water, at carefully chosen sites. Their mission, originally planned for 90 days, has lasted more than two years.

The European Space Agency’s Mars Express mission, launched in 2003, has NASA participation in two of its seven instruments. The spacecraft has been returning color images and other data since January 2004 after entering orbit in December 2003. It has confirmed water ice in Mars’s south polar cap and added information about how the solar wind has been removing water vapor from Mars’ atmosphere for billions of years.

The latest spacecraft, MRO, has a planned five-year prime mission. It also will support the NASA Phoenix Mars Scout being built to land on icy soils near the northern polar ice cap in 2008, and the NASA Mars Science Laboratory, an advanced rover under development for launch in 2009.

Additional information about the Mars Reconnaissance Orbiter is available on NASA’s Web site

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