Closest spacecraft formation flight

The closest spacecraft formation flight is an average of 7.2 km (4.47 mi) apart, achieved by NASA and the MMS Operations Team (both USA) at the Goddard Space Flight Center, Greenbelt, Maryland, USA, on 15 September 2016.

The 4 MMS satellites fly in a tetrahedral formation within the Earth's magnetosphere, in order to capture detailed observations of 'magnetic reconnection'. Magnetic reconnection is where the Sun's magnetic field interrupts the Earth's own magnetic field momentarily, and then reconnects, causing a large burst of energy.

In an official statement, NASA said that "MMS' new, closer formation will allow the spacecraft to measure magnetic reconnection at smaller scales, helping scientists understand this phenomenon on every level,".