

The WFC3/UVIS crosstalk correction algorithm has been developed as an
IDL procedure and is available for use as a standalone routine. The
code, input parameter file, an example WFC3/UVIS image and the
resulting corrected image, as well as a README file can be downloaded
from the WFC3 WWW site.

The program crosstalk_correct_wfc3.pro performs the correction itself.
The code was written assuming that the crosstalk depends linearly on
the offending signal and utilizes the linear regression coefficients
determined from internal dark frames as described in the accompanying
ISR 2012-02.

These coefficients are stored in the input parameter file
'allframes_rgr_st.sav'; this file must be present in the working
directory when using the correction program. Note that while the
correction has been shown to work quite well in a variety of imaging
scenarios, it can be less efficient when the image has a very high,
non-uniform background across field, such as that due to PSF wings in
very crowded stellar fields. 

Observers using the code will want to verify that the correction is
being performed properly for their specific images. The corrected image
is written into the working directory as a fits file with the same name
as the original except the first character is changed to 'x'.

For example, to remove crosstalk from the image iaby01leq, start IDL
and in the working directory containing the program, the .sav file, and
the image, type 

crosstalk_correct_wfc3,'iaby01leq_flt.fits'

The resulting crosstalk-cleaned image, xaby01leq_flt.fits, will be
generated and placed in the working directory. Note that the
xaby01leq_flt.fits available for download from the WWW site has been
renamed to comparison.xaby01leq_flt.fits, to avoid it being
inadvertently overwritten.

Questions or concerns may be sent to help@stsci.edu.

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