VIRCAM Pipeline  2.3.10
vircam_science_process

Science reduction recipe for a full pawprint of VIRCAM data.

Science reduction recipe for a full pawprint of VIRCAM data.

Name:
vircam_science_process
Purpose:
Do a complete science reduction for a full pawprint of VIRCAM data
Description:
A single pawprint of VIRCAM data in a single filter is corrected for instrumental signature. The sky is removed using a defined algorithm and the corrected simple images are dithered into the final stacked image. This stacked image is astrometrically and photometrically calibrated using either locally held catalogues or those queried from the CDS.
Language:
C
Parameters:
General reduction parameters:
  • destripe (bool): If set then the images will be destriped.
  • skyalgo (string): The sky algorithm to be used
    • none: Don't do sky correction
    • master: Use a master sky. This must be included in the sof
    • pawsky_mask: pawsky_mask algorithm
    • pawsky_mask_pre: pawsky_mask with pre-existing object mask
    • tilesky: Used if a full tile is given
    • tilesky_minus: Used if a full tile is given and we excluded the current frame
    • auto: let the routine decide which routine to use
    • pawsky_minus: pawsky_minus algorithm
  • preview_only (bool): If set we only get a preview of the reduction
  • minphotom (int): The minimum number of standards for photometry
  • prettynames (bool): True if we're using nice file names
  • cdssearch (bool): True if we get 2MASS standards from CDS.
  • cacheloc (string): The location of the standards cache
  • magerrcut (float): A cut in the magnitude error for photometric standard stars

Parameters for source detection on stacks:

Parameters for stacking algorithm:

Parameters for the destripe algorithm:

Parameters for pawsky_mask algorithm:

Input File Types:
The following list gives the file types that can appear in the SOF file. The word in bold is the DO category value.
  • OBJECT (required): The list of input science images.
  • OBJECT_EXTENDED (required): The list of input science images with extended sources.
  • SKY_OFFSET (optional): Offset sky observations if available
  • MASTER_DARK (required): A master dark frame.
  • MASTER_TWILIGHT_FLAT (required): A master twilight flat frame.
  • MASTER_SKY (optional): A master sky frame to be used for background correction. If this isn't available, then we look for offset skies. If these aren't available then we use the object images themselves.
  • MASTER_CHANNEL_TABLE (required): The relevant channel table
  • PHOTCAL_TAB (required): A photometric calibration table
  • MASTER_READGAIN_TABLE (required): A master read/gain table
  • MASTER_CONF (required): A master confidence map for the filter used in the science images.
  • MASTER_2MASS_CATLAOGUE (required): A master 2MASS catalogue location (unless using cdssearch).
  • MASTER_OBJMASK (optional): An object mask to be included if the pawsky_mask_pre or pawsky_minus algorithms are requested.
  • SCHLEGEL_MAP_NORTH (required): The Northern Schlegel dust map
  • SCHLEGEL_MAP_SOUTH (required): The Southern Schlegel dust map
Output Products:
The following list gives the output data products that are generated by this recipe. The word in bold gives the DPR CATG keyword value for each product:
  • Copies of the input science frames that have been corrected for instrumental signature and sky (SIMPLE_IMAGE_SCI)
  • Copies of the input offset sky frames that have been corrected for instrumental signature sky (SIMPLE_IMAGE_SKY)
  • A dithered stacked image and its associated confidence map (JITTERED_IMAGE_SCI and CONFIDENCE_MAP_SCI)
  • A catalogue of objects extracted from the stacked image (OBJECT_CATALOGUE_SCI)
  • A mean offset sky frame, if input raw offset skies are given (OFFSET_SKY)
Output QC Parameters:
  • SATURATION The saturation level in ADUs.
  • MEAN_SKY The mean level of the background sky over the image in ADUs.
  • SKY_NOISE The RMS of the background sky over the image in ADUs
  • IMAGE_SIZE The average size of stellar objects on the image in pixels
  • ELLIPTICITY The average ellipticity of stellar objects on the image
  • POSANG The average position angle in degrees from North towards East. NB: this value only makes sense if the ellipticity is significant
  • APERTURE_CORR The aperture correction for an aperture of radius rcore.
  • NOISE_OBJ The number of noise objects found in the image
  • MAGZPT The photometric zero point
  • MAGZERR The internal error in the photometric zero point
  • MAGNZPT The number of stars used to determine the magnitude zero point
  • MAGNCUT The number of stars cut from magnitude zero point calculation
  • SKYBRIGHT The sky brightness in mag/arcsec**2
  • LIMITING_MAG The limiting magnitude for this image for a 5 sigma detection.
  • WCS_DCRVAL1 The offset of the equatorial coordinate represented by CRVAL1 from the raw frame to the reduced one (degrees).
  • WCS_DCRVAL2 The offset of the equatorial coordinate represented by CRVAL2 from the raw frame to the reduced one (degrees).
  • WCS_DTHETA The change in the WCS coordinate system rotation from the raw to the reduced frame (degrees)
  • WCS_SCALE The scale of the pixels in the reduced frames in arcseconds per pixel
  • WCS_SHEAR The shear of the astrometric solution in the form of the difference between the rotation of the x solution and the rotation of the y solution (abs(xrot) - abs(yrot) in degrees)
  • WCS_RMS The average error in the WCS fit (arcsec)
Notes
None.
Fatal Error Conditions:
  • NULL input frameset
  • Input frameset headers incorrect meaning that RAW and CALIB frame can't be distinguished
  • No science frames in the input frameset
  • Required master calibration images and tables are missing
  • Unable to save data products
Non-Fatal Error Conditions:
  • None
Conditions Leading To Dummy Products:
  • Master calibration images either won't load or are flagged as dummy
  • The detector for the current image extension is flagged dead in all science frames
  • Various processing routines fail.
Author:
Jim Lewis, CASU
Code Reference:
vircam_science_process.c