Data Reduction Modules

Functions
int	vircam_illum (casu_fits **images, cpl_table **mstds, cpl_propertylist **pl, int nimages, char *filt, cpl_table *phottab, int nbsize, cpl_table **illcor, float *illcor_rms, int *status)
	Work out the illumination correction.
int	vircam_destripe (casu_fits *in, casu_mask *inbpm, int *status)
	Remove stripes from the background of an image.
int	vircam_genbpm (casu_fits **flatlist, int nflatlist, float lthr, float hthr, cpl_array **bpm_array, int *nbad, float *badfrac, int *status)
	Generate a bad pixel mask from a list of dome flats.
int	vircam_genlincur (double **fdata, int nimages, double *exps, double mindit, casu_tfits *chantab, int norder, cpl_table **lchantab, double **lindata, int *status)
	Generate a linearity curve for each readout channel in a list of images.
int	vircam_lincor (casu_fits *infile, casu_tfits *lchantab, int kconst, int ndit, int *status)
	Apply linearity curves to data.
int	vircam_grout (casu_tfits *intab, cpl_frameset *input_cats, cpl_frameset *input_confs, casu_tfits **outtab, int *status)
	Correct input tile catalogues.
int	vircam_interleave (casu_fits **infiles, int ninputs, casu_fits **inconfs, int nconfs, int nsteps, cpl_propertylist **p, cpl_image **outimage, cpl_image **outconf, int *status)
	Interleave a set of microstepped observations.
int	vircam_mosaic (cpl_frameset *infiles, cpl_frameset *inconf, int interp, int skyflag, float skywish_in, const char *expkey, int conflim, casu_fits **out, casu_fits **outc, int *status)
	Create a vircam mosaic.
int	vircam_tilesky (casu_fits **inlist, int nfiles, casu_mask *mask, casu_fits **skyout, int *status)
	Work sky estimate from an input tile series.

Detailed Description

These are the main processing routines. Most of these also have a test recipe described on the test recipe page.

Function Documentation

vircam_destripe()

int vircam_destripe ( casu_fits * in, casu_mask * inbpm, int * status )

extern

Remove stripes from the background of an image.

Name:

vircam_destripe

Purpose:

Remove stripes from the background of an image

Description:

Remove stripes from the background of an image by finding the median of each row and putting the value into a profile. Normalise the profile to zero median. Then subtract the normalised median for each row from the original data.

Language:

C

Parameters

in	The input image. This is corrected in-situ.
inbpm	The input image bad pixel mask.
status	An input/output status that is the same as the returned values below.

Return values

CASU_OK

if everything is ok

QC headers:

None

DRS headers:

The following DRS keywords are written to the plist propertylist

• STRIPECOR A flag saying that the stripe correction has been done
• STRIPERMS The RMS of the stripe profile

Other headers:

None

Author

Jim Lewis, CASU

Definition at line 87 of file vircam/vircam_destripe.c.

References casu_fits_get_ehu(), casu_fits_get_image(), casu_mask_get_data(), casu_medmad(), casu_medmadcut(), and casu_qmedsig().

vircam_genbpm()

int vircam_genbpm ( casu_fits ** flatlist, int nflatlist, float lthr, float hthr, cpl_array ** bpm_array, int * nbad, float * badfrac, int * status )

extern

Generate a bad pixel mask from a list of dome flats.

Name:

vircam_genbpm

Purpose:

Generate a bad pixel mask from a list of dark corrected dome flat images.

Description:

A list of dark corrected dome flat images is given. A master flat is created from all the input flats in the list. Each input flat is then divided by the master. Bad pixels are marked on the new image as those that are above or below the threshold (in sigma) in the new image. Any pixel which has been marked as bad for more than a quarter of the input images is defined as bad in the output mask.

Language:

C

Parameters

flatlist	The list of input dark corrected dome flat images.
nflatlist	The number of input images
lthr	The low rejection threshold in units of sigma
hthr	The high rejection threshold in units of sigma
bpm_array	The output bad pixel mask
nbad	The number of bad pixels found
badfrac	The fraction of pixels in the map that are bad
status	An input/output status that is the same as the returned values below.

Return values

CASU_OK	If everything is ok
CASU_FATAL	The flat combination failed

QC headers:

None

DRS headers:

None

Author

Jim Lewis, CASU

Definition at line 93 of file vircam_genbpm.c.

References casu_fits_get_image(), casu_getnpts(), casu_imcombine(), casu_medmad(), and casu_medsig().

vircam_genlincur()

int vircam_genlincur ( double ** fdata, int nimages, double * exps, double mindit, casu_tfits * chantab, int norder, cpl_table ** lchantab, double ** lindata, int * status )

extern

Generate a linearity curve for each readout channel in a list of images.

Name:

vircam_genlincur

Purpose:

Generate linearity coefficients for each readout channel of a detector given a median statistic for each channel in a sequence of dome flat field exposures.

Description:

Median flux estimates for each channel in a series of dark corrected dome flat exposures are given along with exposure timing information. The dome exposures must have been taken with a range of exposure times and using a stable light source. From the known reset/read time and exposure times, the linearity curve for each channel can be measured. The resulting coefficients are written to a new channel table, along with an estimate of the non-linearity at a nominal level and an estimate of the quality of the initial fit.

Language:

C

Parameters

fdata	A 2d array of medians for each flat. The first index is the image number. The second index is the channel number.
nimages	The number of input images
exps	An array of exposure times for the input images
mindit	The reset/readout time
chantab	The input channel table
norder	The order of the fit. This will equal to the number of coefficients in the output table as according to the mathematic description of the algorithm, the zeroth coefficient is always zero.
lchantab	The output channel table with new linearity coefficients
lindata	An array of the linearised values of 'fdata'
status	An input/output status that is the same as the returned values below.

Return values

CASU_OK	if everything is ok
CASU_WARN	if one or more channels have a failed fit
CASU_FATAL	if the channel table is invalid.

QC headers:

None

DRS headers:

None

Author

Jim Lewis, CASU

Definition at line 118 of file vircam_genlincur.c.

References casu_tfits_get_table(), vircam_chan_fill(), vircam_chan_free(), vircam_polyfit(), and vircam_solve_gauss().

vircam_grout()

int vircam_grout ( casu_tfits * intab, cpl_frameset * input_cats, cpl_frameset * input_confs, casu_tfits ** outtab, int * status )

extern

Correct input tile catalogues.

Name:

vircam_grout

Purpose:

Correct input tile catalogues for the effects of variable seeing and magnitude zeropoints of the images that went into that tile.

Description:

Variable conditions during the observations of the 6 pawprints of a VIRCAM tile can lead to spatial systematics in the fluxes measured from a tiled image. This routine takes that effect out.

Language:

C

Parameters

intab	The input tile catalogue
input_cats	The catalogues for the input pawprints that formed the tile
input_confs	The confidence maps for the input pawprints that formed the tile
outtab	The output tile catalogue
status	An input/output status that is the same as the returned values below.

Return values

CASU_OK	if everything is ok
CASU_FATAL	if image data fails to load

QC headers:

None

DRS headers:

None

Author

Jim Lewis, CASU

Definition at line 108 of file vircam_grout.c.

References casu_fits_get_image(), casu_fits_load(), casu_med(), casu_tfits_duplicate(), casu_tfits_get_ehu(), casu_tfits_get_table(), and casu_xytoxy_list().

vircam_illum()

int vircam_illum ( casu_fits ** images, cpl_table ** mstds, cpl_propertylist ** pl, int nimages, char * filt, cpl_table * phottab, int nbsize, cpl_table ** illcor, float * illcor_rms, int * status )

extern

Work out the illumination correction.

Name:

vircam_illum

Purpose:

Work out the illumination correction

Description:

Work out the illumination correction from a set of images by dividing the image space into a number of cells. The median of photometric zeropoints for all the stars in a cell is compared with the median zeropoint over the whole set of images.

Language:

C

Parameters

images	The input data images
mstds	The input matched standards catalogues (one for each image)
pl	The list of extension header propertylists (one for each image catalogue)
nimages	The number of images in the input lists
filt	The filter for the observations
phottab	The photometric calibration table for VIRCAM
nbsize	The size of the side of a cell in pixels
illcor	The illumination correction table for this detector
illcor_rms	The RMS of the illumination correction
status	An input/output status that is the same as the returned values below.

Return values

CASU_OK	if everything is ok
CASU_WARN	if there weren't any photometric standards or all the objects in the catalogue failed.
CASU_FATAL	if there is a problem with the photometric calibration table

QC headers:

None

DRS headers:

None

Author

Jim Lewis, CASU

Definition at line 1406 of file vircam_utils.c.

References casu_fits_get_ehu(), casu_fits_get_fullname(), casu_fits_get_image(), casu_fits_get_phu(), casu_medmad(), casu_medmadcut(), casu_medsig(), vircam_illcor_newtab(), vircam_pfits_get_airmass(), and vircam_pfits_get_exptime().

Referenced by vircam_jmp_illum().

vircam_interleave()

int vircam_interleave ( casu_fits ** infiles, int ninputs, casu_fits ** inconfs, int nconfs, int nsteps, cpl_propertylist ** p, cpl_image ** outimage, cpl_image ** outconf, int * status )

extern

Interleave a set of microstepped observations.

Name:

vircam_interleave

Purpose:

Interleave a set of microstepped observations

Description:

A set of microstepped observations and their confidence maps (optional) are given. The cartesian offsets as well as the background medians for each image are also given. The observations and optionally the confidence maps are interleaved onto a finer grid defined by the number of steps in the microstep series. If input confidence maps are given, then an output confidence map will also be generated.

Language:

C

Parameters

infiles	The list of input microstepped observation images. Their extension propertylists need to have: ESO DRS XOFFMICRO (the microstep offset in X), ESO DRS YOFFMICRO (the microstep offset in Y) and ESO DRS BACKMED (the background median). These have to be added by the calling routine.
ninputs	The number of input observation images
inconfs	The list of input confidence maps. If the list is NULL or has a size of zero, then no output confidence map will be created. If the list has a size that is less than the size of the input files list, then only the first one will be used (i.e. each input image has the same confidence map). If the list has the same number as the input images then all of the listed confidence maps will be used to form the output confidence map.
nconfs	The number of input confidence maps
nsteps	The number of steps in the microstep pattern, e.g. for a 3x3 microstep pattern, this should be set to 3.
p	A propertylist that will be used for the output image. This will be the header for the first image in the input image frameset (infiles) with appropriate modifications to the WCS.
outimage	The output interleaved image
outconf	The output confidence map
status	An input/output status that is the same as the returned values below.

Return values

CASU_OK	if everything is ok
CASU_FATAL	if a failure occurs in either accessing input data or the input image list has not images in it.

QC headers:

None

DRS headers:

The following DRS keywords are written to the p propertylist

• PROV**** The provenance keywords

Author

Jim Lewis, CASU

Definition at line 117 of file vircam/vircam_interleave.c.

References casu_crpixshift(), casu_fits_get_ehu(), casu_fits_get_image(), casu_fits_get_phu(), casu_prov(), casu_rescalecd(), and vircam_timestamp().

Referenced by vircam_jmp_interleave().

vircam_lincor()

int vircam_lincor ( casu_fits * infile, casu_tfits * lchantab, int kconst, int ndit, int * status )

extern

Apply linearity curves to data.

Name:

vircam_lincor

Purpose:

Apply linearity curves to data.

Description:

Correct the data in an image for its non-linearity. This is done with the help of a linearity channel table and some basic timing information from the header.

Language:

C

Parameters

infile	The input image. This should probably be a series of dome flat exposures of a stable light source with varying exposure times.
lchantab	The linearity channel table
kconst	If this is set, then the value of k is constant for the image. This is true (for example) if the reset time equals the read time.
ndit	Set to the number of co-adds there are in the input data.
status	An input/output status that is the same as the returned values below.

Return values

CASU_OK	if everything is ok
CASU_FATAL	if the data array can't be mapped for the input image or the linearity channel table is invalid.

QC headers:

None

DRS headers:

The following DRS keywords are written to the infile extension header

• LINCOR The name of the originating FITS file for the linearity table

Author

Jim Lewis, CASU

Definition at line 382 of file vircam_genlincur.c.

References casu_fits_get_ehu(), casu_fits_get_fullname(), casu_fits_get_image(), casu_tfits_get_filename(), casu_tfits_get_table(), vircam_chan_d2r(), vircam_chan_fill(), vircam_chan_free(), vircam_chan_r2a(), vircam_pfits_get_ditdelay(), vircam_pfits_get_exptime(), and vircam_pfits_get_mindit().

vircam_mosaic()

int vircam_mosaic ( cpl_frameset * infiles, cpl_frameset * inconf, int interp, int skyflag, float skywish_in, const char * expkey, int conflim, casu_fits ** out, casu_fits ** outc, int * status )

extern

Create a vircam mosaic.

Name:

vircam_mosaic

Purpose:

Create a mosaic from a list of vircam pawprints

Description:

A mosaic is generated from (nominally six) pawprints of a vircam observation. The backgrounds are matched by scaling to exposure time (which should in theory be all the same, but maybe not...) and by photometric zeropoint. This requires the header item ESO QC MAGZPT to be present. If this is missing then this counts as a fatal error. If they are present, but if any one of them is set to zero, then a warning message is issued but the stacking continues without the photometric scaling.

Language:

C

Parameters

infiles	A frameset with the input stacks
inconf	A frameset with the input confidence maps
interp	The interpolation algorithm: 0 => nearest neighbour, 1 => bilinear interpolation
skyflag	A flag for how you want the sky. 0 => don't adjust the input skies at all, 1 => set the background sky to the value of skywish_in, 2 => set the background sky to the average background for each input image
expkey	The FITS keyword for the exposure time
conflim	A lower limit to be placed on the input confidence. Pixels with confidence below this limit will be ignored.
out	The output mosaic
outc	The output confidence map
status	An input/output status that is the same as the returned values below.

Return values

CASU_OK	if everything is ok
CASU_FATAL	if there was some error detected in the input images

QC headers:

None

DRS headers:

None

Author

Jim Lewis, CASU

Definition at line 167 of file vircam_mosaic.c.

References casu_fits_delete(), casu_fits_get_ehu(), casu_fits_load(), casu_fits_wrap(), and casu_qmedsig().

vircam_tilesky()

int vircam_tilesky ( casu_fits ** inlist, int nfiles, casu_mask * mask, casu_fits ** skyout, int * status )

extern

Work sky estimate from an input tile series.

Name:

vircam_tilesky

Purpose:

Work a sky estimate from an input tile

Description:

A list of images from a whole tile is given. These are broken up into groups that all have the same position within the jitter sequence. An intermediate sky is formed from each group and then a final output sky is formed from the intermediate sky files.

Language:

C

Parameters

inlist	The input images from the tile
nfiles	The number of images in the jitter series
mask	The bad pixel mask derived from the confidence map.
skyout	The output sky map
status	An input/output status that is the same as the returned values below.

Return values

CASU_OK	if everything is ok
CASU_FATAL	if something went wrong. An error message will appear.

Author

Jim Lewis, CASU

Definition at line 94 of file vircam_sky.c.

References casu_fits_get_image(), casu_fits_get_phu(), casu_fits_wrap(), casu_imcombine(), casu_inpaint(), casu_mask_get_data(), casu_mask_get_size_x(), casu_mask_get_size_y(), vircam_pfits_get_jitteri(), and vircam_pfits_get_njsteps().