Design of Instrumentation Suitable for the Investigation of Charge Buildup Phenomena at Synchronous Orbit.

Abstract : A satellite-borne Rapid Scan Particle Spectrometer (RSPD) has been designed to measure the charge buildup phenomena at synchronous orbit. Simultaneous measurements along two orthogonal axes are made. Each axis incorporates 4 electrostatic analyzers (ESA) and 2 solid state spectrometers (SSS). Four ESA's (low energy p, low energy e; high energy p, high energy e) and two SSS's (proton, electron) with four and five energy bins, respectively, in each analyzer provide a logical compromise of energy resolution and high time resolution. The low energy ESA's cover the energy range 0.05 to 1.7 keV; the high energy ESA's cover the 1.7 to 60 keV range. The electron SSS's cover the 30 to 1000 keV range and the proton SSS's cover the 70 to 7000 keV range. A complete energy spectrum is generated every 1 second. The digital data output consists of a 9 bit mantissa and a 3 bit exponent, allowing accumulation of 130,000 counts. A command control allows the ESA or SSS sweep rate to be decreased, or fixed, enhancing the time resolution of portions of the spectrum. A digital count ratemeter with 250 microseconds integration time is included. A multiplexer, controlled by ground command, selects the ratemeter input from one of the 8 ESA's or 8 SSS's. Very high time resolution data can be generated by this circuit. Two instrument's have been fabricated, tested and calibrated. The first of these was launched into near-synchronous orbit on board the SCATHA satellite on 30 January 1979. (Author)