Position Sensitivity Of MAMA Detectors

We report on the results of laboratory and telescopic measurements of the position sensitivity of a visible MAMA. detector utilizing a "coarse-fine" array. We also report on the photometric accuracy of this detector under the condi-tion of point source illumination. The detector measured uses a bialkalai photocathode and has 25 μm2 pixels in a 256 x 1024 format. It was illuminated with a 3.5 pm spot of light (FWHM) which was moved across the detector in 1 μm increments. It is found that computed centroid positions are accurate across the entire array to within 0.04 pixels. For the extreme case of illumination with a delta function source, this detector experienced photometric errors of 10-15%. Both the position sensitivity and the photometric accuracy with point source illumination are limited in this detector by errors in the flat field corrections caused by the presence of cross-coupling between adjacent pixels. Initial measurements with a MAMA detector utilizing a "fine-fine" array indicate that this cross-coupling has been eliminated in the most recent versions of the detector.