The SPEAR (Spectroscopy of Plasma Evolution from Astrophysical Radiation) mission to map the far ultraviolet sky uses micro-channel plate (MCP) detectors with a crossed delay line anode to record photon arrival events. SPEAR has two MCP detectors, each with a ~25mm x 25 mm active area. The unconventional anode design allows for the use of a single set of position encoding electronics for both detector fields. The centroid position of the charge cloud, generated by the photon-stimulated MCP, is determined by measuring the arrival times at both ends of the anode following amplification and external delay. The temporal response of the detector electronics system determines the readout's positional resolution for the charge centroid. High temporal resolution (< 35ps x 75ps FWHM) and low power consumption (<6W) are required for the SPEAR detector electronics system. We describe the development and performance of the detector electronics system for the SPEAR mission.
KEYWORDS: Sensors, Digital signal processing, Control systems, Camera shutters, Electronics, Sun, Spectral resolution, Microchannel plates, Mirrors, Spectrographs
The SPEAR micro-satellite payload consists of dual imaging spectrographs optimized for detection of the faint, diffuse FUV (900-1750 Å) radiation emitted from interstellar gas. The instrument provides spectral resolution, R~750, and long slit imaging of <10' over a large (8°x5') field of view. We enhance the sensitivity by using shutters and filters for removal of background noise. Each spectrograph channel uses identically figured optics: a parabolic-cylinder entrance mirror and a constant-ruled ellipsoidal grating. Two microchannel plate photon-counting detectors share a single delay-line encoding system. A payload electronics system conditions data and controls the instrument. We will describe the design and predicted performance of the SPEAR instrument system and its elements.
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