lsst.obs.decam.crosstalk Namespace Reference

Classes
class	DecamCrosstalkConfig
class	DecamCrosstalkIO
class	DecamCrosstalkTask

Functions
def	subtractCrosstalkIO (mef, sources, coeffs)

Function Documentation

subtractCrosstalkIO()

def lsst.obs.decam.crosstalk.subtractCrosstalkIO	(		mef,
			sources,
			coeffs
	)

Remove crosstalk from a DECam Multi-Extension FITS raw image.

This version uses astropy I/O rather than the Butler due to the cross-amp
crosstalk and ease of accessing Multi-Extension FITS data. It does not
integrate with isr and does not use the Butler.

WARNING: this will run fine on a non-overscan-corrected raw image, but the
crosstalk coefficients were computed post-overscan-correction. Therefore,
**the input raw image should be overscan corrected before this is run.**

Parameters
----------
mef : `astropy.io.fits.hdu.hdulist.HDUList`
    One DECam Multi-Extension FITS image.
sources : `defaultdict`
    Crosstalk source areas affecting flux in a certain victim area.
coeffs : `list`
    Linear crosstalk coefficients.

Returns
-------
mef : `astropy.io.fits.hdu.hdulist.HDUList`
    New MEF image with crosstalk corrected data and updated header.

Definition at line 288 of file crosstalk.py.

def subtractCrosstalkIO(mef, sources, coeffs):
    """Remove crosstalk from a DECam Multi-Extension FITS raw image.
 
    This version uses astropy I/O rather than the Butler due to the cross-amp
    crosstalk and ease of accessing Multi-Extension FITS data. It does not
    integrate with isr and does not use the Butler.
 
    WARNING: this will run fine on a non-overscan-corrected raw image, but the
    crosstalk coefficients were computed post-overscan-correction. Therefore,
    **the input raw image should be overscan corrected before this is run.**
 
    Parameters
    ----------
    mef : `astropy.io.fits.hdu.hdulist.HDUList`
        One DECam Multi-Extension FITS image.
    sources : `defaultdict`
        Crosstalk source areas affecting flux in a certain victim area.
    coeffs : `list`
        Linear crosstalk coefficients.
 
    Returns
    -------
    mef : `astropy.io.fits.hdu.hdulist.HDUList`
        New MEF image with crosstalk corrected data and updated header.
    """
    log = lsst.log.Log.getLogger('obs.decam.subtractCrosstalkIO')
    lowx = {}  # Lower x pixel index of given chip region
    highx = {}  # Upper x pixel index of given chip region
    extension = {}  # FITS extension of given chip position from CCDNUM header
    corrected = [0] * 63  # placeholder for corrected data
 
    for i in range(1, 63):
        ccd = '%02d' % mef[i].header['CCDNUM']
        extension[ccd] = i
        for section in 'AB':
            ccdsec_str = mef[i].header['DATASEC' + section]
            ccdsec_list = re.findall(r"[\w']+", ccdsec_str)
            lowx[ccd + section] = int(ccdsec_list[0]) - 1
            highx[ccd + section] = int(ccdsec_list[1])
        corrected[i] = mef[i].data.astype(np.float32)
    for ccd in ['%02d' % i for i in range(1, 63)]:
        for section in 'AB':
            victim = ccd + section
            victim_data = corrected[extension[ccd]][:, lowx[victim]:highx[victim]]
            for source in sources[victim]:
                source_data = mef[extension[source[:2]]].data[:, lowx[source]:highx[source]]
                if lowx[victim] != lowx[source]:
                    # If regions were read out on different sides of the CCD
                    # (i.e., an A and B mismatch) flip data in the x-direction
                    source_data = np.fliplr(source_data)
                # Perform linear crosstalk correction
                victim_data[:, :] = victim_data - coeffs[(victim, source)] * source_data
                log.info('Correcting victim %s from crosstalk source %s for HDU %s' % (victim, source, ccd))
 
    for i in range(1, 63):
        mef[i].header['HISTORY'] = 'Crosstalk corrected on {0}'.format(
            dt.datetime.now().strftime("%Y-%m-%dT%H:%M:%S"))
        mef[i] = fits.ImageHDU(header=mef[i].header, data=corrected[i])
 
    return mef