between the plasmasphere's outer boundary all the way out to the boundary where the Earth's magnetic field is impacted by the solar wind. The RPI "radar" scans across a spectrum from 3 kilohertz (cycles per second) up to 3 megahertz, spanning the entire AM radio band and beyond. Every five minutes, an image was built from the returned radio signals that will contain information about the direction, speed and density of distant plasma clouds. The instrument was developed by a team led by Dr. Bodo Reinisch, University of Massachusetts at Lowell. The Central Instrument Data Processor (CIDP) provided acquisition, compression, storage and telemetry formatting of science data from all imagers, routes commands to the imagers and interfaces with the spacecraft systems. The CIDP was developed by SwRI. Lost contact On 18 December 2005, the satellite failed to make an expected contact at 16:20 UTC. An earlier contact had ended successfully at 07:39 the same day with no sign of trouble. Over the following days and weeks, commands were sent "blind" to reset the transmitter, change antennas, and otherwise attempt to re-establish contact with the spacecraft, but no signal (not even an unmodulated carrier wave) was received. Recovery efforts included using different NASA Deep Space Network (NASA DSN) antennas, using non-NASA ground stations in case there was some systematic NASA DSN error, transmitting no commands for several days to trigger a 72-hour watchdog timer, increasing transmit power in case the antenna was badly misaligned, and optical and radar observations of the satellite to check for debris, change in spin rate or change in orbit indicative of a collision or other damage. The spacecraft was also commanded to slightly increase its spin rate and asymmetrically turn on its heaters. If observed, these would indicate that it could receive commands but not transmit. Neither change was seen and analysis later indicated that the temperature change would have been undetectable. An attempt to observe the craft's temperature to determine if it was completely dead or consuming the power expected in safe mode was inconclusive. A careful failure analysis revealed that, among plausible causes for an abrupt bidirectional loss of communication, the Solid State Power Converter (SSPC) for the transponder had, among its features, an "instant trip" shutdown in response to a high-current () short circuit. Critically, such a shutdown was not reported in the power supply's telemetry output and this lack was not documented.