Quality Control: linearity

VIRCAM Quality Control:
detector linearity

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QC PLOTS
	CURRENT	HISTORY
detector non-linearity
fraction of bad pixels
flux variation
QC1 database (advanced users): browse \| plot
Click on CURRENT to see the current trending (Health Check). Click on HISTORY to see the historical evolution of the trending.

top non-linearity

QC1 parameters

parameter	QC1 database: table, name	procedure
qc_linearity	vircam_line, qc_linearity, qc_linerror, qc_nbadpix, qc_badfrac	- The non-linearity is derived from a series of dome flat exposures with different flux levels. The reference flux is at 10000 ADU. qc_linearity is the percentage of non-linearity at 10000 ADU.
halogen lamp performance	vircam_line, qc_screen step, qc_screen_total	- The calibration unit consists of several halogen lamps illuminating a screen in the VISTA enclosure. Both parameters monitor intrinsic illumination instabilities and failures of individual lamps.

top ranges and saturation

QC1 parameters

parameter	QC1 database: table, name	procedure
qc_line_medmin , qc_line_medmax	vircam_line, qc_line_medmin, qc_line_medmax	- The post-pipeline QC script measures the mode flux in all flat frames. The highest flux and the lowest mode flux of all raw flat frames is taken. (mode means: the maxium of the flux histogram is taken.). Since the detector is operated in double correlated read out mode, which is composed by three sequential events: reset, read read. The detector requires DET.MINDIT seconds to reset and read all pixel of the detector. DET.MINDIT=1.0011 sec (2009-12-01). The detector acquisition system subtracts the flux taken between the reset and the first read from the flux measured after the second read and writes it into the frame. Hence the measured flux in a flat does correspond to DIT seconds exposure time. For reasons to check the flux versus the saturation level, the flux acquired in DIT + MINDIT seconds must be compared. The qc_lin_medmin and qc_line_medmax are corrected for the DIT+MINDIT exposure times: *qc_line_medmax = flux (DIT+MINDIT)/DIT**. The correction is only relevant for small DIT, large lamp fluxes, and large MINDIT.
dit_min, qc_dit_max	vircam_line, qc_dit_min, qc_dit_max	- The post-pipeline script takes the largest and the smallest used DET.DIT from the linearity sequence

Saturation

Each detector has a different saturation level. The saturation levels in ADU are (2009-09):

Detector #5 has the lowest saturation level

From 2009-11-20 on, ( after the video channel card replacement for chip #6 ) the saturation levels are: