<title>Flexible configuration for the Lyman FUSE fine-error sensor</title>

Abstract

The fine error sensor (FES) system is a star tracker like device that is used within the Lyman far ultraviolet spectroscopic explorer (FUSE) instrument. The FES extends the performance achievable from the conventional star trackers by providing very low noise guidance reference signals. In addition the FES is used for scene and target identification for the UV system operation. This is accomplished by the FES looking through the Lyman FUSE telescope system by means of a pick-off mirror at an intermediate image. This paper describes the proposed readout electronics for the FES CCD and the CCD clock driving system. The clock driving system is unique in that software can reconfigure the hardware required to generate the various CCD clocks and the timing signals for the readout electronics. An adaptable method used to define the location of the six sub-rasters, used to identify the selected guide stars, is described. A variable clocking rate is utilized to minimize readout time while minimizing read noise. The benefits of using RAM based field programmable gate array (FPGA) technology for flight programs also is highlighted.