• Launch: 3 August 2004
• Orbital Insertion: 18 March 2011
• End of missions: 30 April 2015
• Agency: NASA
MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) is a scientific investigation of the planet Mercury, the least explored terrestrial planet.
MESSENGER, with its seven instruments, will be the first mission to orbit Mercury and only the second mission to visit this planet closest to the Sun. Understanding Mercury and its history is essential to understanding the origin and evolution of the other terrestrial planets. To get into orbit around Mercury, it must follow a complex path through the inner solar system, using one flyby of Earth, two flybys of Venus, and three flybys of Mercury for gravity assists. This impressive journey has already returned the first new data from Mercury in more than 30 years from its January 14, 2008 flyby.
MESSENGER launched on August 3, 2004, returned to Earth for a gravity boost on August 2, 2005, then flew past Venus on October 24, 2006 and June 5, 2007. It completed the first of three Mercury flybys on January 14, 2008 and will return on October 6, 2008 and September 29, 2009. The spacecraft uses these planetary flybys to resize and rotate its trajectory in order to achieve orbit around Mercury in March 2011. The Mercury flybys will also map the unseen side of the planet and yield science data to guide planning for the year-long orbital mission. MESSENGER’s instruments will map nearly the entire planet in color, image the surface in high resolution, and measure the composition of the surface, atmosphere and nature of the magnetic field and magnetosphere.