An Instrument for the Measurement of Auroral Electrons and Protons

An instrument to measure the energy spectrum of auroral electrons and protons has been developed and is operational in orbit aboard ATS-5. It uses cylindrical coordinate electrostatic analyzers for detection of electrons and protons in the range of 50 eV to 50 keV. The analyzers focus these particles onto channel electron multipliers, which are followed by special-purpose amplifier-discriminator electronics. These electronics protect against counting losses due to gain degradation attributable to fatigue and to recovery effects associated with high counting rates. The pulse amplifiers have a dynamic range of 1000:1 and resolve 1-??s pulse pairs. Their fixed dead time (td) permits accurate correction to be made for counting rates exceeding l/td. A fast, ultrastable, programmable high-voltage scan system provides differential voltages between 0 and 6400 V in 62 exponential steps to the analyzer plates for energy selection. A digital servo permits either continuous sequential scanning over the 1000:1 range in energy, or automatic tracking of a spectral peak. Digital compression techniques are used to provide maximum data transfer to the spacecraft telemetry.