24 August 2011 UPDATE

Latest news on the Pixel-CTE Correction code and its incorporation into CALACS:

The ACS team is currently testing a new version of CALACS containing two significant improvements: automatic removal of bias stripes using the pre-scan region; and pixel-based CTE correction.

In addition to the standard data products (crj, flt and drz files) there will be three new files (crc, flc and drc) which will contain the CTE-corrected data products. Users will be able to choose whether to use the standard or CTE-corrected products. Both sets of data will be stripe corrected. This new version of CALACS applies the CTE correction to the raw images and requires CTE-corrected dark reference files. The ACS team is currently making these for the entire ACS archive. We hope to have the new CALACS running in the data reduction pipeline in October/November this year.

At present, the development version of the new CALACS is available in IRAFX. Users who run IRAFX will find that they cannot run CALACS because they do not have the new reference (PCTE) file or the CTE-corrected dark reference files. The code is still being developed and tested and we recommend that users do not seek to CTE-correct their data using the new CALACS at this stage.

At this time, we recommend that users continue to use the stand-alone version of the pixel-CTE code that works on flt images and is available via CTE tutorial site . This version can be accessed from IRAF or PYRAF and is based on the Anderson & Bedin (2010), ACS ISR 2010-03 code.

The new CALACS incorporates a refined version of the Anderson & Bedin (2010) code. It is more effective at low flux levels (< 100 electrons), and employs a more accurate time and temperature dependence for CTE over the ACS lifetime. A stand-alone version of this CTE code, working on the flt images, exists and is available under ACSTOOLS in IRAFX. Users will not be able to run this version because a new version of the reference (PCTE) file is required. If you have a particular need to run this, please contact the helpdesk and request the file. Please note that this version is still being tested/developed. At this time, there is no documentation describing either the revised CTE algorithm or how to run the codes, so only expert users should consider trying our development stand-alone code. This code may also change in IRAFX without warning as we continue to develop it.