On board control is provided by a Pumpkin FM430 flight control module containing a Texas Instruments MPS430 microcontroller. Communications are provided by a half-duplex UHF modem with a 1.5 Mbit/s downlink (465 MHz) and 19.2 kbit/s uplink (450 MHz). The satellites carry four Electric Field Probe sensors on telescopic booms, two DC Langmuir probes for detection of ions and a three-axis magnetometer for measuring magnetic fields.