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Hubble Space Telescope
ACS CTE Information

The charge transfer efficiency (CTE) of the ACS CCDs (WFC and HRC) is declining as damage from the space radiation environment accumulates. Here we provide information about our efforts to monitor CTE, and methods of mitigating and calibrating it.


The ACS/WFC CTE Correction Calculator corrects ACS/WFC aperture photometry for CTE losses using the most recent formula from Chiaberge's ISR 2012-05 and updated coefficients based on cycle 20 calibration data.This tool is only calibrated for photometry obtained after SM4 in May 2009. For pre-SM4 data, please see Chiaberge et al. 2009 (ISR 2009-01), or use pixel-based CTE-corrected files obtained from MAST. As of 2015, we offer the capability for using post-flash to alleviate the effects of CTE and for guidelines on the use of post-flashing see the following webpage: ACS WFC Post-Flash Capabilities

Related Reports

A new accurate CTE photometric correction formula for ACS/WFC (ISR 12-05)

CTE White Paper, June 29, 2012

Empirical Pixel-Based Correction for Imperfect CTE (ACS ISR 2010-03)

Pixel-based correction for CTI in the HST ACS (ACS ISR 2010-01)

Updated CTE photometric correction for WFC and HRC (ACS ISR 2009-01)

Internal monitoring of ACS CTE (ACS ISR 2005-03)

Time Dependence of ACS WFC CTE Corrections for Photometry and Future Predictions (ACS ISR 2004-06)

Elevated temperature measurements of ACS CTE (ACS ISR 2004-04)

WFC radiation test (ACS ISR 2000-09)

AAS Posters

CTI over the History of the ACS WFC poster for AAS Meeting, January 2011

Post-SM4 ACS CTE poster for AAS Meeting, January 2010

ACS CTE poster for AAS Meeting, January 2003


Internal monitoring of ACS CTE:
Post-SM4 EPER and FPR for WFC
Pre-SM4 EPER and FPR for WFC and HRC

Internal (EPER/FPR) CTE programs:
8948, 9561, 9569, 9570, 9571, 9572, 9649, 9707, 10044, 10369, 10370, 10732, 11045, 11881, 12386

External (47 Tuc) CTE programs:
9648, 10043, 10368, 10730, 11044, 11510, 11880, 12385

CTE Working Group (1999-2000)

Group membership and charter

Workshop at STScI in January 2000

Reference Library

HST CTE in the second decade (WFC3 ISR 2001-05)


Pixel-based CTE correction page for WFC

Justification for onboard FPR/EPER CTE calibration (ACS TIR 1999-03)