ACIS Instrument Information
Recent memos: Update on ACIS contaminant, Jan 8 2010
The Advanced CCD Imaging Spectrometer (ACIS) is an X-ray imager. X-ray photons hitting the camera are detected individually and their position, energy and arrival time recorded. This allows for high resolution (~1 arcsec) imaging, moderate resolution spectroscopy and timing studies. ACIS can also be used with the High Energy Transmission Grating (and less commonly the Low Energy Transmission Grating) for high resolution spectroscopy.
The Instrument layout is shown to the right. The back illuminated S3 chip offers the best spectral resolution without using a grating. For this reason, many observers choose the back illuminated S3 chip for high resolution imaging over small (few arcminutes) fields. The largest field of view is obtained by turning on the 4 ACIS-I front illuminated chips. This configuration is often used for surveys. The table below summarizes common instrument configurations, although others are available.
A complete description of ACIS is given in the ** Proposers’ Observatory Guide**.
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Printed 2026-06-28.
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