An Electron Spectrometer for Project Gemini

A spectrometer design to measure the flux and energy of electrons present at Gemini orbital altitudes is briefly described. The instrument utilizes a thick lithium drifted silicon detector, coupled with a 50 micron dE/dx silicon wafer and plastic scintillator to detect electrons of energy 0.25 ¿ E¿4.0 Mev. Straightforward pulse height analysis employing tunnel diode discrimination feeds a specially designed, fully digital data processor. When connected to the spacecraft PCM telemetry system, a seven energy channel spectrum is sampled every 1.3 seconds. Dynamic range of the instrument is sufficient to handle omnidirectional fluxes of up to 106/cm2-sec. A special collimator provides an aperture of 0.25 steradian so that particle direction, as well as intensity, can be determined.