NASA has been prepping Messenger for more than six years since its launch in August of 2004 for conducting experiments while orbiting the innermost planet of our solar system.
Messenger entered Mercury's orbit on March 17 and is planned to activate its scientific instruments on March 24. The first tests are scheduled to take place on April 4, while NASA said that it will be posting first images of Mercury beginning March 29. It is the first time in more than 35 years when Mariner 10 flew past Mercury in 1974 and 1975 and photographed about 45% of mercury's surface.
While Messenger's primary research goal is to collect information about the composition and structure of Mercury's crust, its geologic history, the nature of its thin atmosphere and active magnetosphere, as well as the structure of its core and polar materials, it will also complete the surface imagery of the planet. Since its launch from Cape Canaveral, Messenger flew 15 times around the sun, twice past Venus (2006 and 2007) and three times past Mercury (January 2008, October 2008 and September 2009).
NASA used the fly-bys to fine-tune Messenger's speed and added more imagery, which increased the existing coverage of Mercury's surface area to 75%.