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MESSENGER Mission News
September 22, 2009

Experience MESSENGER's Third Mercury Flyby Virtually
See Mercury through the “eyes” of MESSENGER’s imagers with the Mercury Flyby Visualization Tool, now available at http://messenger.jhuapl.edu/encountersm3/. This updated Web feature offers a unique opportunity to see simulated views of Mercury from MESSENGER’s perspective, during approach, flyby, and departure, or in real-time (as the observations actually occur).

This tool combines one of the best available image maps of Mercury’s surface with observation sequences for the Mercury Dual Imaging System (MDIS), Mercury Atmospheric and Surface Composition Spectrometer (MASCS), and Mercury Laser Altimeter (MLA). The map of Mercury’s surface combines high-resolution image mosaics from the Mariner 10 spacecraft flybys of Mercury in 1974 and 1975 and images from MESSENGER's first two flybys of Mercury in January and October of last year.

There are many helpful tips available on the pages of this visualization tool. Pointing and clicking on any color bar will display the projection of each completed image mosaic on Mercury or show the end of the active MLA or MASCS observation. Information accompanying each simulated image includes the latitude and longitude of the point at the center of each image, the resolution in meters (or kilometers when farther from the planet) per pixel (picture element) at the image center, the altitude (how far the spacecraft is above Mercury's surface), and the time relative to closest approach.

One Week to Mercury Flyby 3 - A Look at the Planned Imaging Coverage

Just one week from today, MESSENGER will pass a mere 228 kilometers (142 miles) above the surface of Mercury for the mission's third flyby of the Solar System's innermost planet. This figure shows the planned imaging coverage for the upcoming encounter. The area of the surface that will be imaged by MDIS during Mercury flyby 3 is outlined in yellow, and it includes a portion of Mercury's surface never before seen by spacecraft.

“Because the spacecraft velocity relative to Mercury is about one-third slower at Mercury flyby 2 than at Mercury flyby 2, the gravity-assist turn angle to the spacecraft’s trajectory increases from about 27° to nearly 50°,” explains Jim McAdams, the MESSENGER mission design lead engineer. “This greater bend in the trajectory provided by the gravity of Mercury offers the spacecraft its first opportunity to view a small portion of Mercury’s surface twice with different vantage points and nearly identical lighting conditions just a few hours apart.”

Prior to the MESSENGER mission, only 45% of Mercury's surface had been seen by the Mariner 10 spacecraft. As shown in this figure, with the completion of MESSENGER's three Mercury flybys, nearly all of Mercury's surface will have been viewed at close range by spacecraft, with the exception of the polar regions. Along with imaging of previously unseen terrain, other imaging activities planned for Mercury flyby 3 include a high-resolution southern-hemisphere mosaic during departure and targeted observations of specific surface features selected on the basis of their importance for understanding the diversity of compositions among Mercury surface materials.

Tomorrow, on September 23, NASA will host a media teleconference previewing the flyby. Details of that event will be posted online at http://messenger.jhuapl.edu/news_room/index.php.

MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.

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