The vmdet recipe

vmdet

Synopsis

Determine RON, gain, and bad pixels from a set of flat field exposures.

Description

This recipe is used to estimate the read-out-noise (RON) and the gain of the CCD, and to determine the positions of the bad pixels.

The input SOF should contain at least five pairs of flat field exposures, all belonging to the same quadrant, each pair corresponding to a different exposure time. The flat fields can be produced either in imaging or in MOS mode. In MOS mode a HR grism is used, in order to illuminate the CCD also beyond the central region used in direct imaging mode, but no mask is inserted at the telescope focal plane.

This type of exposure cannot really be considered a spectral flat field, because the CCD is exposed to white light (i.e., without a wavelength dependency along the dispersion direction). The flat fields generated for the purpose of determining the detector properties are assigned the DO category DETECTOR_PROPERTIES, to distinguish them from the more common IMG_SCREEN_FLAT or MOS_SCREEN_FLAT that are used to produce master calibrations.

Input files

DO category:          Type:         Explanation:  Required:
DETECTOR_PROPERTIES   Raw           Flat field       Y
MASTER_BIAS           Calib         Master bias      Y

Output files

DO category:          Data type:    Explanation:
CCD_TABLE             FITS table    Bad pixel table
(none)                FITS image    Bad pixel image
(none)                FITS image    Error image

Only the primary product, the bad pixel table, is copied (or moved) to the product directory. Other products are generated only on request (typically for debug purposes) and are not assigned a DO category as they would not be used anywhere in further data processing steps.

For more details, please refer to the VIMOS Pipeline User’s Guide.

Constructor

cpl.Recipe("vmdet")

Create an object for the recipe vmdet.

import cpl
vmdet = cpl.Recipe("vmdet")

Parameters

vmdet.param.CreateBadPixelMap

Bad pixel map creation (bool; default: True) [default=True].

vmdet.param.CreateErrorImage

Response slope uncertainty map creation (bool; default: False) [default=False].

vmdet.param.DetectionThreshold

Threshold in determination of bad pixels (float; default: 5.0) [default=5.0].

vmdet.param.DetectionMode

Bad pixel detection method (str; default: ‘Intolerant’) [default=”Intolerant”].

vmdet.param.ComputeQC

Compute QC1 parameters. (bool; default: True) [default=True].

The following code snippet shows the default settings for the available parameters.

import cpl
vmdet = cpl.Recipe("vmdet")

vmdet.param.CreateBadPixelMap = True
vmdet.param.CreateErrorImage = False
vmdet.param.DetectionThreshold = 5.0
vmdet.param.DetectionMode = "Intolerant"
vmdet.param.ComputeQC = True

You may also set or overwrite some or all parameters by the recipe parameter param, as shown in the following example:

import cpl
vmdet = cpl.Recipe("vmdet")
[...]
res = vmdet( ..., param = {"CreateBadPixelMap":True, "CreateErrorImage":False})

See also

cpl.Recipe for more information about the recipe object.

Bug reports

Please report any problems to ESO VIMOS Pipeline Team. Alternatively, you may send a report to the ESO User Support Department.