Messenger Spacecraft Successfully Enters Mercury's Orbit

NASA's Messenger spacecraft successfully achieved orbit around Mercury at 9pm Eastern Thursday night, the first time a spacecraft has accomplished this feat, NASA announced.

While in orbit, Messenger (MErcury Surface, Space ENvironment, GEochemistry and Ranging) will be as close as 124 miles from the surface of Mercury. It is now 28.67 million miles from the sun and 96.35 million miles from Earth.

Around 8:45pm, the spacecraft's main thruster was fired in order to slow it down enough to be "captured" by Mercury, NASA said. It fired for about 15 minutes and slowed Messenger by 1,929 miles per hour, a process that consumed 31 percent of the propellent that the spacecraft had at launch. It had about 9.5 percent of its fuel left after the orbit insertion process, but NASA said it will have plenty of propellant left to complete its mission.


In the next few weeks, APL engineers will make sure the spacecraft's systems are functioning in Mercury's harsh thermal environment. Mercury is close enough to the sun that it's 11 times brighter on the planet than it is on Earth, and surface temperatures can reach about 840 degrees Fareheit. There are pockets of the planet, however, that are constantly shaded, so temperatures there can drop to minus 350 degrees Farenheit. But Messenger was built using a composite material that makes the spacecraft relatively light, and it will stay cool via a sunshade made of heat-resistant ceramic cloth, NASA said.

If all goes well, the spacecraft's instruments will be activated on March 23 and the primary science phase will begin on April 4.


