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Hubble Space Telescope
Advanced Camera for Surveys

The Advanced Camera for Surveys (ACS) is a third-generation Hubble Space Telescope (HST) instrument. ACS was installed during HST servicing mission 3B. During servicing mission 4, the ACS WFC was repaired after an electronics malfunction in 2007.

ACS Web Tools

ACS Zeropoint Calculator

ACS CTE Correction Calculator

Late Breaking News

News Archive

30 Aug 2018 ISR 18-04 by J. Anderson and J.E. Ryon, "Improving the Pixel-Base CTE-correction Model for ACS/WFC" is no posted

31 May 2018 ISR 18-03 by S. Hoffmann et al., "A Minor Contamination Event in May 2017 Affecting the ACS/WFC CCD's" is now posted

17 Apr 2018 ISR 17-09 by J. Mack et al, "ACS/WFC Sky Flats from Frontier Fields Imaging." is now posted

29 Mar 2018 ISR 18-02 by N. Miles, "Updates to Post-Flash Calibration for the Advanced Camera for Surveys Wide Field Channel" is now posted.

16 Mar 2018 ISR 17-10 by S.E. Deustua and J. Mack, "Comparing the ACS/WFC and WFC3/UVIS Calibration and Photometry" is now posted.

16 Feb 2018 ISR 18-01 by V. Kozhurina-Platais et al, "Accuracy of the HST Standard Astrometric Catalog w.r.t. Gaia" is now posted.

29 Dec 2017 ISR 17-13 by J.E. Ryon et al, "Accounting for Readout Dark in ACS/WFC Superbiases" is now posted.

29 Dec 2017 ISR 17-06 by A. Bellini et al, "Post-Flash Validation of the new ACS/WFC Subarrays" is now posted.

27 Oct 2017 ISR 17-08 by S.L Hoffmann and J. Anderson, "A Study of PSF Models for ACS/WFC" is now posted.

11 Sept 2017 ISR 17-12 by A. Bellini et al, "The Hubble Space Telescope "Program of Last Resort" is now posted.

Software Updates

In January of this year, the ACS Team released a version of CALACS, version 10.0.0, that will be installed with the most recent version of HSTCAL, v2.0.0, as part of the HSTDP 2018.1 pipeline release. This version contains all the updates made to CALACS v9.2.0, in addition to the several improvements made in v10.0.0. This release is the largest since CALACS in HSTDP 2012.2 containing many updates and improvements to the calibration routines used in CALACS.

Out-dated Webpages

In light of these updates, the ACS Team is currently working to update all webpages referencing previous versions of CALACS. This is a work in progress and so whenever possible, we strongly recommend that users refer to the documentation in the most recent version of the ACS Data Handbook (v9.0) published in February 2018. If you are still unable to find an answer to your question, please submit a help ticket at We apologize for any inconvenience this may cause and thank you for bearing with us.

-The ACS Team

A brief summary of the major updates to CALACS in v9.2.0 and v10.0.0 are as follows:

Updates in v9.2.0

  • The implementation of sink pixel corrections (SINKCORR) resulting in updated Data Quality arrays (See ISR 17-02)
  • The implementation of an updated pixel based CTE correction (ISR 18-04 in progress)
  • The addition of the Data Quality bit flag, 32, which characterizes pixels to be unstable throughout the course of an anneal period (See ISR 17-05)
  • An enhanced bias level correction that now correctly calculates the bias level for amplifiers B and D in subarrays
  • MAST Newsletter for September 2017: The New CALACS

Updates in v10.0.0

  • A bug that resulted in incorrect error propagation for CRSPLIT observations combined with ACSREJ has been fixed
  • The ACSREJ algorithm has been updated to use the ERR arrays when rejecting cosmic rays
  • Amp-dependent read noise thresholds were implemented in the CTE correction
  • A bug affecting CRSPIT data with PCTECORR=PERFORM that caused the non-cte corrected superdark to be used in dark subtraction has been fixed.

Release notes for all HSTCAL versions are posted in the github repository.

Current ACS Status

SBC is operating nominally.

HRC is not operational.

WFC is operating nominally.