Report of findings The IMAGE satellite contains a sweep-frequency radio sounder, the Radio Plasma Imager (RPI), used to probe the surrounding plasma environment. We studied signals detected by RPI during the inbound part of the orbit, at altitudes ranging from 1500 km to 20,000 km. Several periods, in particular May to August 2004, yielded an abundance of records on echoes and resonances appearing in frequency ranges unanticipated by cold plasma theory, as well as a related class of echoes in the Whistler mode (WM) domain. These phenomena are now believed to be effects of proton gyrations occurring close to the satellite, surrounded by a plasma sheath. Read report (PDF)