A Small Instrument for Low Energy Particle Observations in the Heliosphere

Abstract

We describe a lightweight and low-power sensor to measure energetic ions from solar, galactic, and heliospheric sources. This sensor is based on the Low Energy Telescopes (LETs) carried by the Voyager spacecraft as part of the Cosmic Ray Subsystem. The energy range of the particles detected can be adjusted by altering the detector thicknesses, but the nominal Voyager LET responds to all nuclei from protons· through nickel (Z = l to 28) over energy ranges of ~0.5 to 8 Me V for protons and ~5 to 30 Me V /nucleon for iron. We also discuss the characteristics of the electronics required to support the sensor. The analog electronics would consist of custom VLSI circuits of low mass and low power. The digital electronics would require an Actel gate array and a microprocessor. The detectors would require biases up to ~100 V. Assuming that low voltages woul4 be supplied from a common supply on the spacecraft that services all instruments, the total weight and power of such a system is ~250 g and 400 mW.