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A Pivotal Moment
Click on image to enlarge.
A Pivotal Moment
Release Date: July 8, 2011
Topics: Limb Images, WAC



Date acquired: June 21, 2011
Image Mission Elapsed Time (MET): 217120645
Image ID: 405150
Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
WAC filter: 7 (748 nanometers)
Center Latitude: -40.58°
Center Longitude: 150.0° E
Resolution: 2799 meters/pixel
Scale: Mercury's radius is approximately 2440 km (1516 miles)
Incidence Angle: 48.5°
Emission Angle: 48.1°
Phase Angle: 73.0°

Of Interest: This image, captured with the Wide Angle Camera (WAC), was taken using MDIS’s pivot. MDIS is mounted on a pivoting platform and is the only instrument in MESSENGER’s payload capable of movement independent of the spacecraft. The other instruments are fixed in place, and most point down the spacecraft’s boresight at all times, relying solely on the guidance and control system for pointing. The 90° range of motion of the pivot gives MDIS a much-needed extra degree of freedom, allowing MDIS to image the planet’s surface at times when spacecraft geometry would normally prevent it from doing so. The pivot also gives MDIS additional imaging opportunities by allowing it to view more of the surface than just that at which the boresight-aligned instruments are pointed at any given time. To capture this image, the pivot was placed at an angle of about 5 degrees relative to the spacecraft's boresight.

This image was acquired as part of MDIS's limb imaging campaign. Once per week, MDIS captures images of Mercury's limb, with an emphasis on imaging the southern hemisphere limb. These limb images provide information about Mercury's shape and complement measurements of topography made by the Mercury Laser Altimeter (MLA) of Mercury's northern hemisphere.

The MESSENGER spacecraft is the first ever to orbit the planet Mercury, and the spacecraft's seven scientific instruments and radio science investigation are unraveling the history and evolution of the Solar System's innermost planet. Visit the Why Mercury? section of this website to learn more about the key science questions that the MESSENGER mission is addressing. During the one-year primary mission, MDIS is scheduled to acquire more than 75,000 images in support of MESSENGER's science goals.

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington


For information regarding the use of MESSENGER images, see the image use policy.


   

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