Quality Control and
Data Processing

HC PLOTS
dark current
dark_current (before 2002-04)
QC1 database (advanced users): browse | plot

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
[Calculated by QC procedure]	fors2_dark..dark_avg	average dark current over frame (e/px/hr)	HC		[docuSys coming]
[Calculated by QC procedure]	fors2_dark..sigma_dark_avg	sigma dark current over frame (e/px/hr)	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 averaged over frame (e-/pix/hr) is trended here. For data before 2002-04 look here.

Scoring&thresholds DARK current

The dark current level is scored with dynamic thresholds following the median average of the current period. The only requirement is stability on the calibration timescale.

History

The high DARK values observed after January 2008 are due to pickup noise according to Thomas Szeifert (statement from May 3rd, 2008).

Algorithm DARK current

The median level of the master dark is normalized per pixel and hour and converted into electrons.

As the error of the dark current is dominated by the read-out noise, it is calculated from the read-out noise provided in the header, scaled with the exposure time (as it is normalized to 1 hour)

For the old CCD (in use until March 22, 2002) the dark current was computed from the median master dark frame level in ADU/hr/px and transformed into electrons by using the conversion factor CONAD (in the case of 4 port readout a mean CONAD was used). Also the dark current per port was calculated and stored in the QC1 Database (dark_A(BCD), sigma_dark_A(BCD)).