A Unique Rocket-Borne Data Handling System for Solar X-Ray Studies

Abstract

A high-speed, high-resolution spectrometer system has been designed for the detection and analysis of low-energy x-rays from a spinning rocket. The system enjoyed a highly successful flight in the spring of 1967 and another flight is currently scheduled for the fall of 1967. The system was comprised of four large-area beryllium-window proportional counters, an analog pulse-height-to-time converter, a digital data assembler and a complete PCM multiplexer. The system was capable of analyzing x-ray events at average input rates in excess of 50,000 events per second. The pulse-height-to-time converter, in conjunction with a portion of the digital data assembler, formed a 64-channel pulse-height analyzer and provided an energy resolution of 0.5 keV per channel over the 3-30 keV energy range of the detectors. The data assembler, using a non-linear, lump digital decoding technique, compiled and stored a complete spectrum on board the rocket. Channel address accumulators were completely buffered so that while one spectrum was being time multiplexed to telemetry, another was being accumulated. This technique gives rise to very short dead-time periods and enabled the detector and pulse-height converter to operate in random-access fashion at high input rates. The PCM multiplexer portion of the system time multiplexed all of the spectral information, along with absolute rate data, and applicable timing and I.D. information into a serial Non-Return-to-Zero-Level (NRZL) formatted binary output with sufficient drive to directly modulate an FM transmitter. The multiplexer operated from a single, stable 20 kHz oscillator.