September 21, 2016 – On September 15, 2016, NASA’s Magnetospheric Multiscale (MMS) mission achieved a new record: Its four spacecraft are flying only four-and-a-half miles apart, the closest separation ever of any multi-spacecraft formation. The previous record was first set by MMS in October 2015, when the spacecraft achieved a flying separation of just over six miles apart.
MMS gathers data to study a phenomenon called magnetic reconnection, which occurs when the magnetic field surrounding Earth connects and disconnects from the magnetic field carried by the solar wind, reconfiguring the very shape of Earth’s magnetic environment. Magnetic reconnection can result in the explosive release of energy that can accelerate particles to incredible speeds – in some cases to nearly the speed of light. The MMS orbit is designed to carry the spacecraft directly though reconnection events.
The four MMS spacecraft fly in a tetrahedron formation, with one satellite marking each corner. This allows MMS to capture three-dimensional observations of magnetic reconnection – critical for fully understanding this process. The close formation is all the more impressive as the spacecraft speed along at up to 15,000 miles per hour and – with their booms extended – each spacecraft covers as much area as a professional baseball stadium.
MMS’ new, closer formation will allow the spacecraft to measure magnetic reconnection at smaller scales, helping scientists understand this phenomenon on every level.
The MMS spacecraft depend on GPS signals for such close proximity. Each spacecraft has eight GPS antennae so that as the spacecraft rotate, an algorithm allows one antenna to hand-off to the next without losing the signal. So far, the MMS “Navigator system” has been more accurate than expected.
NASA launched the four spacecraft on a single United Launch Alliance Atlas V rocket from Cape Canaveral Air Force Station, Florida, on March 12, 2015.
MMS is the fourth NASA Solar Terrestrial Probes (STP) program mission. Goddard built, integrated and tested the four MMS spacecraft and is responsible for overall mission management and mission operations. The Southwest Research Institute in San Antonio, Texas, leads the Instrument Suite Science Team, with the University of New Hampshire leading the FIELDS instrument suite. Science operations planning and instrument command sequence development are performed at the MMS Science Operations Center at the University of Colorado’s Laboratory for Atmospheric and Space Physics in Boulder.