Uhuru (satellite) - Instrumentation

Instrumentation

The payload consisted of two sets of proportional counters, each with ~0.084 m2 effective area. The counters were sensitive with more than 10% efficiency to X-ray photons in the ~2-20 keV range. The lower energy limit was determined by the attenuation of the beryllium windows of the counter plus a thin thermal shroud that was needed to maintain temperature stability of the spacecraft. The upper energy limit was determined by the transmission properties of the counter filling gas. Pulse-shape discrimination and anticoincidence techniques were used to reduce the background due to particles and high-energy photons. Pulse-height analysis in eight energy channels was used to obtain information on the energy spectrum of the incident photons. The two sets of counters were placed back to back and were collimated to 0.52° X 0.52° and 5.2° X 5.2° (full width at half maximum) respectively. While the 0.52° detector gave finer angular resolution, the 5.2° detector had higher sensitivity for isolated sources.