The design features and the performances of a prototype photon counting imaging detector, being developed for the international ultraviolet (UV) space mission Spectrum UV, are presented. The photon counter is an intensified charge coupled device (ICCD) in which photon events, generating an electron cascade through a high gain microchannel plate (MCP) stack, are transduced, via a phosphor screen and a fiber optics reducer, into a 3×3 pixel2, quasi-Gaussian charge distributions on a 15×15 μm2,512×512 pixel2 format CCD matrix. The CCD is read out in the frame-transfer mode at a pixel rate of 19.75 MHz, and its output data flow is acquired serially as to generate a 3×3 pixel2 event sash that sweeps dynamically the CCD matrix at the 50.6 ns rate of the readout clock. Each and every event sash is searched for the presence of events whose charge content lie within proper limits and satisfy a given set of morphological rules, i.e., a single peak charge profile. The centroid coordinates of identified events are determined with subpixel accuracy (up to a 210 bin/pixel) and subsequently stored as photon list coordinate pairs. The data acquisition and processing system is based on field programmable gate array technology and is capable of satisfying the requirements of real-time operation. The modular construction of the data acquisition and processing electronics provides a great deal of flexibility for supporting advancements in CCD readout techniques (multiple output and higher clocking speed) and of MCPs (larger formats, smaller pore, and higher dynamic range). The results of the performance verification of the data acquisition and processing - system integrated with a laboratory ICCD prototype are presented and discussed. © 2000 American Institute of Physics.