A high sensitivity telescope for measurements of energetic particles in the Earth's radiation belts

The High Sensitivity Telescope (HST) is a sensor comprising part of the Loss Cone Imager (LCI) on the DSX mission. The primary objective of the HST is to observe fluxes of energetic electrons as small as 100 e cm-2sr-1s-1 within the Earth's atmospheric loss cone. This is accomplished via a geometrical factor of 0.1 cm2sr combined with a collimator limiting the field of view to a 7 degree half-cone angle. The sensors are shielded to in order to reduce the background to levels permitting the detection of the stated flux. The HST will be looking for changes in this flux caused by events precipitating electrons into the atmosphere. Of primary interest are electrons with energies between 20 and 500 keV. The HST utilizes two fully depleted solid state detectors and three analog measurement chains. The primary detector is 1500 um thick and uses two measurement chains. A faster measurement chain for counting events at rates of 300k/sec and a slower measurement chain for measuring the energy deposited by an event more accurately. The secondary detector is 1000 um thick and is used to detect events that completely penetrate the primary detector. The analog electronics are built from discreet amplifiers. Events on the faster primary chain are sorted into 5 energy bins. Events from the slow chain are digitized to 8-bits of resolution.