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NASA maps Mercury, plans for 2011 orbit extravaganza

NASA Mercury mission will send MESSENGER satellite around planet 730 times

By Layer 8 on Wed, 12/16/09 - 4:55pm.

NASA Mercury Mosiac NASA's Mercury planet exploration team this week said they have created critical tool for the first orbital observations of the planet - a global map of Mercury that will help scientists pinpoint craters, faults, and other features that will be essential for the space agency's extensive 2011 mission.

That's when NASA's satellite MESSENGER (The MErcury Surface, Space ENvironment, GEochemistry, and Ranging, or MESSENGER) will become the first spacecraft to actually orbit Mercury -- about 730 times -- beaming back pictures and never-before-available pictures and information on the planet. To get into its proper orbit, MESSENGER has taken the scenic route through the solar system, including one flyby of Earth, two flybys of Venus, and three flybys of Mercury.

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NASA's MESSENGER mission team and cartographic experts from the U. S. Geological Survey came up with the map which was created from images taken during the Messengers' three flybys of the planet and those of Mariner 10, NASA said. In the 1974 and 1975 NASA's Mariner 10 satellite flew by the planet and gave the world its first close-up view of Mercury, the closest planet to the Sun.

Making the map or mosaic was no easy feat. The challenging part has been to make cartographically accurate maps from a series of images with varying resolution (from about 100 to 900 meters per pixel) and lighting conditions (from noontime high Sun to dawn and dusk) taken from a spacecraft traveling at speeds greater than 2 kilometers per second (2,237 miles per hour)," says Arizona State University's Mark Robinson, a member of the MESSENGER Science Team.

Once in orbit MESSENGER has a variety of tools at its disposal. For example, MESSENGER has two cameras -- one wide-angle, and one narrow-angle -- to help the "two-eyed" Mercury Dual Imaging System (MDIS) create a map of the planet's landforms, NASA said. It will also trace different features on the surface. A special pivoting platform allows scientists to point the MDIS in whatever direction they choose.

The Mercury Laser Altimeter (MLA) will create topographic maps of the planet's surface in unprecedented detail, NASA stated. When the laser shines down and reflects off Mercury's surface, a sensor will gather the light, allowing scientists to track variations in the distance from the surface to the spacecraft. A Radio Science experiment will use the Doppler Effect to track the changes in MESSENGER's velocity, and translate them into clues to how the planet's mass is distributed and where the crust is thicker or thinner, NASA said.

Three instruments will rely on a process called spectroscopy to tell scientists what elements are present in the rocks and minerals around the planet. The X-ray Spectrometer (XRS) will detect X-rays emitted by certain elements in Mercury's crust. The Gamma Ray and Neutron Spectrometer (GRNS) works in much the same way, detecting gamma rays and neutrons emitted by various elements. GRNS may also help to determine if water ice really exists in permanently-shadowed craters at the planet's north and south poles -- as previous observations suggest. The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) will be able to determine Mercury's atmosphere and also detect minerals on the surface. The instrument is extremely sensitive to light from the infrared to the ultraviolet, NASA said.

Some Mercury facts from NASA:

Mercury has a diameter of 3,032 miles, about two-fifths of Earth's diameter. Mercury orbits the sun at an average distance of about 36 million miles (58 million kilometers), compared with about 93 million miles for Earth.
Because of Mercury's size and nearness to the brightly shining sun, the planet is often hard to see from the Earth without a telescope. At certain times of the year, Mercury can be seen low in the western sky just after sunset. At other times, it can be seen low in the eastern sky just before sunrise.
Mercury travels around the sun in an elliptical (oval-shaped) orbit. The planet is about 28,580,000 miles from the sun at its closest point, and about 43,380,000 miles from the sun at its farthest point. Mercury is about 48,000,000 miles from Earth at its closest approach.
Mercury moves around the sun faster than any other planet. The ancient Romans named it Mercury in honor of the swift messenger of their gods. Mercury travels about 30 miles per second, and goes around the sun once every 88 Earth days. The Earth goes around the sun once every 365 days, or one year.
As Mercury moves around the sun, it rotates on its axis, an imaginary line that runs through its center. The planet rotates once about every 59 Earth days -- a rotation slower than that of any other planet except Venus. As a result of the planet's slow rotation on its axis and rapid movement around the sun, a day on Mercury -- that is, the interval between one sunrise and the next -- lasts 176 Earth days.

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