A NASA mission to fly five small spacecraft through explosive geomagnetic disturbances to discover what triggers the northern and southern auroras. The five spacecraft were launched on 17 February 2007, from Cape Canaveral, into highly elliptical orbits: probe 1 orbital period 4 days, perigee 1.500 Earth radii (RE), apogee 31.645 RE; probe 2 period 2 days, perigee 1.168 RE, apogee 19.770 RE; probe 3 period 1 day, perigee 1.118 RE, apogee 12.127 RE; probe 4 period 1 day, perigee 1.118 RE, apogee 12.127 RE; probe 5 period 0.8 day, perigee 1.350 RE, apogee 10.044 RE.