An Empirical Pixel-Based Correction for Imperfect CTE. I. HST’s Advanced Camera for Surveys

By Jay Anderson, L. Bedin. 2010

218 citations recorded by the source corpus.

We use an empirical approach to characterize the effect of charge-transfer efficiency (CTE) losses in images taken with the Wide-Field Channel of the Advanced Camera for Surveys (ACS). The study is based on profiles of warm pixels in 168 dark exposures taken between 2009 September and October. The dark exposures allow us to explore charge traps that affect electrons when the background is extremely low. We develop a model for the readout process that reproduces the observed trails out to 70 pixels. We then invert the model to convert the observed pixel values in an image into an estimate of the original pixel values. We find that when we apply this image-restoration process to science images with a variety of stars on a variety of background levels, it restores flux, position, and shape. This means that the observed trails contain essentially all of the flux lost to inefficient CTE. The Space Telescope Science Institute is currently evaluating this algorithm with the aim of optimizing it and eventually providing enhanced data products. The empirical procedure presented here should also work for other epochs (e.g., pre-SM4), though the parameters may have to be recomputed for the time when ACS was operated at a higher temperature than the current -81°C. Finally, this empirical approach may also hold promise for other instruments, such as WFPC2, STIS, the ACS’s HRC, and even WFC3/UVIS.

Subfields: Astronomy and Astrophysics, Biomedical Engineering, Electrical and Electronic Engineering

View Paper: https://www.semanticscholar.org/paper/8da55aaa0a932855ebf202c4d7293997ede37fd9

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Citations in the corpus

The Hubble Space Telescope UV Legacy Survey of Galactic globular clusters – IX. The Atlas of multiple stellar populations (2016, methodology): “All the images have been corrected for the effect of poor charge transfer efficiency following Anderson & Bedin (2010).”
THE EVOLUTION OF THE GALAXY REST-FRAME ULTRAVIOLET LUMINOSITY FUNCTION OVER THE FIRST TWO BILLION YEARS (2014, methodology): “Although algorithms have been devised to correct for this (Anderson & Bedin 2010), we do not include the CANDELS I814 photometry in the initial photometric redshift fitting (although we do explore its inclusion in Section 3.6), because the CANDELS fields have imaging in both the i775 and z850 bands.”
H0LiCOW - IV. Lens mass model of HE 0435-1223 and blind measurement of its time-delay distance for cosmology (2016, methodology): “The images are reduced using MultiDrizzle4 with charge transfer inefficiency taken into account (e.g., Anderson & Bedin 2010; Massey et al. 2010).”
Origins of weak lensing systematics, and requirements on future instrumentation (or knowledge of instrumentation) (2012, methodology): “A much more robust technique, demonstrated by Leauthaud et al. (2010), is to apply a physicallymotivated correction scheme at the pixel level as the first process during data reduction (e.g. Massey 2010; Anderson & Bedin 2010).”
THE QUENCHING OF THE ULTRA-FAINT DWARF GALAXIES IN THE REIONIZATION ERA (2014, methodology): “Reduction The images were processed with the latest pipeline updates, including a pixel-based correction (version 3.2) for chargetransfer inefficiency (CTI; Anderson & Bedin 2010) resulting from radiation damage to the ACS detectors.”
TWO ACCURATE TIME-DELAY DISTANCES FROM STRONG LENSING: IMPLICATIONS FOR COSMOLOGY (2012, methodology): “We reduce the images using MultiDrizzle12 with charge transfer inefficiency taken into account (e.g., Anderson & Bedin 2010; Massey et al. 2010).”
THIRD-EPOCH MAGELLANIC CLOUD PROPER MOTIONS. I. HUBBLE SPACE TELESCOPE/WFC3 DATA AND ORBIT IMPLICATIONS (2013, background): “There is no explicit model for the underlying HRC CCD detector physics and charge trap properties, as there now is for other cameras (Anderson & Bedin 2010).”
GLOBULAR CLUSTERS IN THE OUTER GALACTIC HALO: NEW HUBBLE SPACE TELESCOPE/ADVANCED CAMERA FOR SURVEYS IMAGING OF SIX GLOBULAR CLUSTERS AND THE GALACTIC GLOBULAR CLUSTER AGE–METALLICITY RELATION (2011, methodology): “Before performing photometry on the individual images, they were corrected for charge transfer efficiency using the algorithm developed by Anderson & Bedin (2010).”
The behaviour of dark matter associated with four bright cluster galaxies in the 10 kpc core of Abell 3827 (2015, methodology): “We corrected this trailing using the software of Massey et al. (2010b, 2014) for the ACS/WFC and Anderson & Bedin (2010); Anderson (2014) for WFC3/UVIS.”
CANDELS: THE CONTRIBUTION OF THE OBSERVED GALAXY POPULATION TO COSMIC REIONIZATION (2012, background): “Recently obtained ACS imaging suffers from poor charge transfer efficiency; this can be corrected for detectable sources (Anderson & Bedin 2010), but at this point it is unclear whether robust upper limits can be obtained from these data.”
UV-CONTINUUM SLOPES AT z ∼ 4–7 FROM THE HUDF09+ERS+CANDELS OBSERVATIONS: DISCOVERY OF A WELL-DEFINED UV COLOR–MAGNITUDE RELATIONSHIP FOR z ⩾ 4 STAR-FORMING GALAXIES (2011, methodology): “After using public codes (e.g., Anderson & Bedin 2010) to correct the raw frames for charge transfer efficiency defects and row-by-row banding artifacts, we performed the alignment, cosmic-ray rejection, and drizzling with the ACS GTO apsis pipeline (Blakeslee et al. 2003).”
CANDELS: THE COSMIC ASSEMBLY NEAR-INFRARED DEEP EXTRAGALACTIC LEGACY SURVEY—THE HUBBLE SPACE TELESCOPE OBSERVATIONS, IMAGING DATA PRODUCTS, AND MOSAICS (2011, methodology): “…algorithm that carries out a fit to the deferredcharge trail behind each bright pixel and redistributes the charge into the pixels in a way that is intended to represent the original flux as detected, before any CTE degradation (as implemented by Anderson & Bedin 2010; see also Massey 2010).”
Techniques and Review of Absolute Flux Calibration from the Ultraviolet to the Mid-Infrared (2014, background): “2014 PASP, 126:711–732 in the HST in 1997, while Anderson & Bedin (2010) provide a good example of a CTE correction.”
3D-HST: A WIDE-FIELD GRISM SPECTROSCOPIC SURVEY WITH THE HUBBLE SPACE TELESCOPE (2012, methodology): “Finally, bias striping (Grogin et al. 2010) and chargetransfer efficiency (CTE) (Anderson & Bedin 2010) corrections are applied to the ACS FLT pipeline products.”
THE 2012 HUBBLE ULTRA DEEP FIELD (UDF12): OBSERVATIONAL OVERVIEW (2012, methodology): “A key point about the CTE correction algorithm (Anderson & Bedin 2010). is that it is effectively a deconvolution, by virtue of the fact that it restores the charge profiles of pixels along a particular column to their original shape, which is sharper and more concentrated than the observed…”
THE CLUSTER LENSING AND SUPERNOVA SURVEY WITH HUBBLE: AN OVERVIEW (2011, methodology): “The ACS/WFC data, however, are first corrected for bias-striping and chargetransfer efficiency (CTE) degradation effects (Anderson & Bedin 2010).”
UVUDF: ULTRAVIOLET THROUGH NEAR-INFRARED CATALOG AND PHOTOMETRIC REDSHIFTS OF GALAXIES IN THE HUBBLE ULTRA DEEP FIELD (2015, methodology): “In addition, we apply a pixel- based CTE correction19 to the raw data based on empirical modeling of hot pixels in dark exposures (Anderson & Bedin 2010; Massey et al. 2010).”
THE PANCHROMATIC HUBBLE ANDROMEDA TREASURY. X. ULTRAVIOLET TO INFRARED PHOTOMETRY OF 117 MILLION EQUIDISTANT STARS (2014, methodology): “Thus, we found that the CTE-corrected images produce more reliable centroids than the flt images, showing the high-quality of the on-image CTE-correction algorithm (Anderson & Bedin 2010).”
THE STELLAR INITIAL MASS FUNCTION OF ULTRA-FAINT DWARF GALAXIES: EVIDENCE FOR IMF VARIATIONS WITH GALACTIC ENVIRONMENT (2013, methodology): “Stars were then blindly recovered and corrected for charge transfer (Anderson & Bedin 2010).”