Exploration Mission 2 or EM-2 is scheduled as the first manned mission of NASA's Orion project, which is to restart manned exploration of the Solar System. NASA plans to launch it as early as 2021, to take a two person crew, for the first time, to a captured asteroid in lunar orbit. In the event this mission proceeds, it will (barring earlier flights by other agencies) be the first time humans have left low earth orbit since Apollo 17 in December 1972.
EM-2 is a single launch mission of a Block IB SLS with an Exploration Upper Stage, lunar Block 1 Orion Multi-Purpose Crew Vehicle (MPCV) and a Payload insertion of 50.7 t. It would be a ten to fourteen day mission with a crew of four astronauts who would spend four days in lunar orbit. Its current description is “Crewed mission to enter lunar orbit, test critical mission events, and perform operations in relevant environments”. The destination for EM-2, as of 2013, is considered a captured asteroid, in lunar orbit, to be conducted by no later than 2021. The destination could possibly be 2000 SG344 although there are a number of other options.