Performance of the wedge-and-strip microchannel plate detectors and electronics for the Global Ultraviolet Imager

This paper describes the design and performance of the detectors and electronics developed for the Global UV Imager (GUVI) aboard the NASA TIMED spacecraft, to be launched in May 2000. GUVI employs two alternate design detectors that are compact sealed units with MgF windows, CsI photocathodes, and wedge-and-strip anodes. The focal plane is 15.6 mm X 16.5 mm with images quantized to 176 spectral by 14 spatial pixels, although access to image data over the entire 25-mm dia active area is provided. Moderate detector resolution is achieved at a relatively low gain. Science emphasis is on high throughput, good image stability, and high radiometric accuracy. Significant detector aging is anticipated over an extended mission with sustained high counting rates. Custom hybrid front-end electronics were developed to enable direct coupling to the wedge-and-strip anodes. This eliminates inter-electrode potentials and the associated image distortion and shift with counting rate. A parallel fast channel provides pulse pile-up rejection. XY position, binning, and compression algorithms are performed in software by a fast, radiation- hardened RISC processor. A full-custom ASIC counts input and output rates for each detector.