Quality Control and
Data Processing

HC PLOTS
dark current and particle rate
QC1 database (advanced users): browse | plot

he OmegaCAM dark template consists of three, one-hour exposures taken with the camera shutter closed. It is normally taken every 10 days. The processing consists of rejecting the cosmic ray events and subtracting the bias level. The remaining signal above the bias level is the dark signal, given in units of ADU/pixel/hour. For the reduction of subsequent on-sky observations the subtraction of the sky brightness will include the dark current, and a separation of both contributions is normally not required.

The pipeline creates one output frame from its dark recipe (omega_darkcurrent): a mean dark (OC_MDAR_<DATE>_1_1_normal_normal.fits).

An OmegaCAM mean dark (single detector) frame. The mean dark has had its mean bias level subtracted and each pixels displays its dark current in units of ADU/hour. An OmegaCAM master bias (single detector) as computed

The master bias frames from detectors ESO_CCD_#68 and #90 have a pronounced central ridge. This is stable and can be well subtracted. Therefore, these features are tolerated, but can create a larger number of hot pixels when compared to other detectors.

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
QC.DARK.CURRENT	omegacam_dark..qc_dark_current	dark current (ADU/pixel/hour)	HC		[docuSys coming]
QC.PARTICLE.RATE	omegacam_dark..qc_particle_rate	mean number of particles (particles/cm^2/hour)	HC		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

The dark current and particle rate averaged over all 32 extensions (ADU/pixel/hour) are plotted in box 1 and box2 of the trending plot. Box 4 shows scores for each CCD.

Scoring&thresholds DARK current

The averaged dark current and particle rate are loosly scored, with static thresholds following the median average of the current period. The only requirement is stability on the calibration timescale.

History

Date	event
2020-11-15	CCD77 does not work; only displays random signal consistent with noise (PPRS-079377)
2020-11-15	CCD69 shows blob in upper border; visible in bias but more evident in darks (PPRS-079620)
2022-05-09	CCD77 started recording some coherent signal again

History

The master dark frames, dark current, and particle rates have been very stable for all OmegaCAM detectors.

Algorithm DARK current

the OmegaCAM dark template consists of three, one-hour exposures taken with the camera shutter closed. The processing consists of rejecting the cosmic ray events and subtracting the bias level. The remaining signal above the bias level is the dark signal, given in units of ADU/pixel/hour. For the reduction of subsequent on-sky observations the subtraction of the sky brightness will include the dark current, and a separation of both contributions is normally not required.

The particle event rate is determined by the detected number of cosmic ray events (particles/cm^2/hour).