Of Interest: This is the cover of the MESSENGER "Phase 1" proposal submitted to the NASA Discovery Program in response to the 1996 call for proposals. Discovery is NASA's lowest-cost class of planetary space mission. The competition is open to any category of spacecraft investigation. In order to be selected, the MESSENGER mission to Mercury had to beat out tens of other proposals for missions, including other Mercury missions. The Phase 1 (initial) proposal, with a launch in September 2002 to reach Mercury orbit in February 2007, was selected for a Feasibility Study (along with Aladdin [Phobos and Deimos sample return], Venus Environmental Satellite, and resubmissions of CONTOUR [comet nucleus tour] and Genesis [solar-wind sample return]). The MESSENGER Feasibility Study was submitted to NASA in August 1997. MESSENGER was not selected for flight at that time (Genesis and CONTOUR were selected). The MESSENGER mission was re-proposed at the next opportunity in June 1998 in response to NASA Announcement of Opportunity 98-OSS-04. This proposal was accepted for further study as were INSIDE Jupiter, Deep Impact, re-proposed Aladdin, and Venus Sounder for Planetary Exploration. The MESSENGER Concept Study, submitted in March 1999, identified a prime launch opportunity in March 2004 as well as a backup opportunity in early August 2004. Following a site visit to APL by the Discovery review panel in April 1999, MESSENGER was selected for flight as the seventh Discovery mission (with Deep Impact as number eight). The MESSENGER project formally started on 1 January 2000.*

*Information culled from McNutt et al. (2006), Advances in Space Research, vol. 38, 564–571.

A reprint of the paper is available here.

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, MESSENGER acquired 88,746 images and extensive other data sets. MESSENGER is now in a yearlong extended mission, during which plans call for the acquisition of more than 80,000 additional images to support 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.