Chandra X-Ray Observatory
Last modified: 7 September 2018


This keyword gives the exposure time of a single ACIS frame and is quantized in units of 0.1 s with the shortest EXPTIME being 0.2 s. It excludes the time during which charge is moved from the imaging region to the frame store region (0.04104 s).

The standard value of EXPTIME = 3.2 s for TIMED mode ACIS observations. If an observation uses interleaved mode then there are separate values of EXPTIME for the short and long frames (e.g. 0.2 s and 3.2 s, respectively).

The observation times entry and the chandra times help file explain how the various exposure keywords are related.

Last modified: 7 September 2018
Smithsonian Institute Smithsonian Institute

The Chandra X-Ray Center (CXC) is operated for NASA by the Smithsonian Astrophysical Observatory. 60 Garden Street, Cambridge, MA 02138 USA.   Email: Smithsonian Institution, Copyright © 1998-2017. All rights reserved.