An image is a matrix of numbers that represent the values of a measured physical quantity at different points in space. The images returned by MESSENGER's MDIS camera measure the amount of light reflected from the surface of Mercury. There is a myriad of ways in which the image values can be presented for display. The translation from the inherent physical values of the image to the "digital numbers" of a computer display is referred to as the "image stretch." Here we have the same image of an area of the terminator in two different stretches. The left-hand image nicely presents the better-illuminated portions of the scene, but some details in the darker areas cannot be seen. The right-hand image has a "harsher" stretch that permits some areas of low illumination to be perceived, at the expense of saturating areas that received more sunlight. North is to the top in each image.
This image was acquired as part of MDIS's high-resolution surface morphology base map. The surface morphology base map covers more than 99% of Mercury's surface with an average resolution of 200 meters/pixel. Images acquired for the surface morphology base map typically are obtained at off-vertical Sun angles (i.e., high incidence angles) and have visible shadows so as to reveal clearly the topographic form of geologic features.
Date acquired: October 28, 2011
Image Mission Elapsed Time (MET): 228323253
Image ID: 943659
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: -14.60°
Center Longitude: 159.1° E
Resolution: 149 meters/pixel
Scale: The large crater near the bottom of the image is about 38 km (24 mi.) in diameter
Incidence Angle: 88.9°
Emission Angle: 15.1°
Phase Angle: 104.0°
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 acquired 88,746 images and extensive other data sets. MESSENGER is now in a year-long extended mission, during which plans call for the acquisition of more than 80,000 additional images to support MESSENGER's science goals.
These images are from MESSENGER, a NASA Discovery mission to conduct the first orbital study of the innermost planet, Mercury. For information regarding the use of images, see the MESSENGER image use policy.