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Smear Campaign
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Smear Campaign
Release Date: January 26, 2012
Topics: Global Views, Limb Images, Mercury Flyby 1, NAC



Date acquired: January 15, 2008
Image Mission Elapsed Time (MET): 108874364
Image ID: 5014
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: -16.43
Center Longitude: 201.6 E
Scale: The diameter of Mercury is about 4880 km (3032 mi.).
Note that North is toward the bottom in these non-map-projected views.

Of Interest: Here we see three views of an image collected during MESSENGER's first flyby of Mercury in January 2008. The top two images have had a harsh contrast stretch applied, to emphasize portions of the image with low signal levels. Notice that in the top left image there are bright streaks in the sky that extend from the edge of the planet toward the bottom of the image. These streaks are the result of "frame-transfer smear." An image exposed on the NAC's detector array is transferred to a memory zone in which the image is digitized, with the shift of each pixel's signal moving from top to bottom. The NAC, like most spacecraft cameras, does not have a shutter. Light continues to fall on the array during the approximately 4 milliseconds that are needed to complete the shift. As a result, some of the light is "misplaced" in the final raw image. It is a straightforward calibration step to remove the smear by subtracting the signal due to the extra light striking each pixel. The image in the upper right is shown with the same contrast stretch after application of the frame-transfer smear correction. The image on the bottom is the same calibrated image with a normal contrast stretch applied, allowing features on the surface of Mercury to be visible.

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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