MAMA detectors are capable of delivering signal-to-noise ratios on the order of 100:1 per resolution element (2 ×2 pixels) or even higher. Tests in orbit have demonstrated that such high S/N is possible with STIS (Kaiser et al., PASP, 110, 978; Gilliland, STIS ISR 1998-16
). For targets observed at a fixed position on the detector, the signal-to-noise ratio is limited by systematic uncertainties in the small-scale spatial and spectral response of the detector. The MAMA flats show a fixed pattern that is a combination of several effects including beating between the MCP array and the anode pixel array, variations in the charge-cloud structure at the anode, and low-level capacitive cross-coupling between the fine anode elements. Intrinsic pixel-to-pixel variations are of order 6% but are stable to < 1%.
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