Ful Sky Astrometric Mapping Explorer, FAME, CCD Centroiding Experiment

摘要

FAME is a MIDEX astrometry mission designed to map the positions of 40,000,000 stars to an accuracy of 50 micro-arc seconds. Optimized between mission requirements, size, weight, and cost, the FAME instrument consists of a 0.6 x 0.5 m~2 aperture whose point spread function central peak is linearly sampled by two pixels. To achieve its astrometric mapping mission requirements, this instrument must achieve a single look centroiding accuracy on a visual magnitude 9.0 (or brighter) star of <0.003 pixels while operating the focal plane in a time domain integration, TDI, mode. As this performance requirement represents a significant improveemnt over the current state of the art of 0.02 to 0.01 pixel resolution, a risk reduction experiment was conducted to determine our centroding ability using a flight traceable CCD operated in TDI mode. An ultra-stable optical system was configured to project a simulated starfield onto the CCD which was mounted on a high precision moveable stage. Moving the stage across the projected starfield in synchronization with the TDI rate simulated the sensing environment expectged in the final instrument, and intensities were adjusted to simulate 9~(th) visual magnitude stars. Experimental results demonstrated single look centroiding accuracy of <0.002 pixels in addition to yielding unexpected dividends in refining CCD operations and centroid data analysis. This paper describes the experiemnt design, centroiding results, CCD operating techniques and data analysis methods.