A Proportional Counter Spectrometer for the Study of the Solar Soft X-Ray Spectrum

An instrument, containing seven proportional counter detectors, has been designed for flight on the N.A.S.A. Orbiting Solar Observatory-D. The wavelength band 1 - 18Å is divided into 24 energy intervals by means of pulse height analysis. Five detectors are employed in this wavelength range; two of them provide low sensitivity alternatives at the short wavelength end of the range. Low sensitivity detectors are selected automatically by the instrument in response to increased solar X-ray activity. Two additional detectors are employed for the 44 - 55Å and 44 - 62Å wavelength bands. A calibration system, employing radioactive sources, is used for "in flight" calibration of all the detectors and electronic systems. Detectors are connected sequentially to a single main amplifier and eight-channel pulse height analyser. A data compression system is employed to make economical use of the available telemetry words. High voltages for the detectors are derived from two inverter circuits which employ corona stabiliser tubes. Two redundant inverter circuits provide low voltage supplies for the instrument. A spectrum in the range 1 - 18Å can be obtained every sixteen seconds.