On May 20, 2013, the Magnetospheric Multiscale, or MMS, mission team at NASA's Goddard Space Flight Center in Greenbelt, Md., reached an unprecedented milestone. The team mated the instrument and spacecraft decks to form the fourth and final MMS observatory. This is the first time Goddard has simultaneously engineered this many observatories, or spacecraft, for a single mission.

Source: NASA's Magnetospheric Multiscale team assembles final observatory