In-flight performance of the MAMA detectors on the Space Telescope Imaging Spectrograph

The Space Telescope Imaging Spectrograph (STIS) is a versatile HST instrument covering the 115-1000 nm wavelength range in a variety of spectroscopic and imaging modes. Coverage of the ultraviolet range (115-310 nm) is provided by two Multi-Anode Microchannel Array (MAMA) detectors built by Ball Aerospace. The FUV MAMA covers the 115-170 nm range using an opaque CsI photocathode on the microchannel plate; the NUV MAMA covers the 165-310 nm range using a semi-transparent Cs₂Te photocathode on the detector window. Both MAMAs utilize a 1024×1024 anode format, but detected photon events are positioned to half the spacing of the anode lines, leading to a 2048×2048 format for the final readout. The active area of each detector is 25.6×25.6 mm. Since the installation of STIS onto the Hubble Space Telescope (HST) in February 1997, the MAMAs have carried out a varied program of astronomical observing and in-flight calibration. The detectors have performed extremely well. In this report, we briefly describe the design of the STIS MAMA detectors, provide illustrative examples of their scientific use on HST, and summarize their technical performance in orbit, in such areas as sensitivity, resolution, flat-field uniformity and stability, signal-to-noise capability, dynamic range, and background.