As MESSENGER neared Mercury on January 14, 2008, the spacecraft's Wide Angle Camera on the Mercury Dual Imaging System (MDIS) took images of the planet through each of its 11 filters. This image of the planet's full crescent was taken using the 7th filter, in light near the far-red end of the visible spectrum (750 nm). The image shows portions of Mercury previously seen by Mariner 10, but when Mariner 10 flew by the planet at each of its encounters the Sun was nearly overhead. For this MESSENGER flyby, in contrast, the Sun is shining obliquely on regions near the day/night boundary (called the terminator) on the right-hand side of the crescent, revealing the surface topography in sharp relief. This image illustrates how MESSENGER, during its future flybys and subsequent orbital mission, will teach us much about the portion of Mercury already imaged by Mariner 10, and not just because of its superior camera and close proximity to the planet. The solar lighting geometry makes an enormous difference.
A day after its successful flyby of Mercury, the MESSENGER spacecraft turned toward Earth on Tuesday and began downloading the 500 megabytes of data that had been stored on the solid-state recorder during the encounter. All of those data, including 1,213 images from the Mercury Dual Imaging System (MDIS) cameras, have now been received by the Science Operations Center at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. Preliminary analysis of these data by the MESSENGER Science Team has confirmed that all seven MESSENGER instruments are healthy and operated as planned during the flyby.
As MESSENGER flew by the planet, it missed its targeted aim point by only 5.12 miles (8.25 kilometers), affording the critical gravity assist needed to continue on a course to become, in 2011, the first spacecraft ever to orbit Mercury. During this first encounter, the payload successfully conducted a carefully orchestrated sequence of observations designed to take full advantage of the geometry of the flyby trajectory and to optimize the science return from each instrument.
In addition to images of the previously unseen portion of the planet's surface, measurements were made that will contribute to the characterization of all aspects of Mercury and its environment, from its metallic core to the far reaches of its magnetosphere. "We have one excited science team," says MESSENGER Project Manager, Peter D. Bedini, of APL, "and their enthusiasm is contagious."
The analysis of these data is just beginning, but there are already indications that new discoveries are at hand.
This picture provides a global context for the MDIS Narrow Angle Camera (NAC) images taken while MESSENGER was inbound. This image was taken about 80 minutes before closest approach from a distance of about 17,000 miles (27,000 kilometers) and shows features as small as 6 miles (10 kilometers). NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
