Integrated circuits, manufactured in CMOS technology, have been develo
ped as diffusion-based charged particle spectrometers for space applic
ations. Current designs are single-chip spectrometers capable of uniqu
ely identifying and counting electrons and heavy ions. A four-chip spe
ctrometer designed to count protons and heavy ions was flown on the Cl
ementine spacecraft. The spectrometer proton data is compared to GOES-
6 proton data for the 21 February 1994 solar proton event.