QC PLOTS
	CURRENT	HISTORY
flat stability
bad pixels
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Click on CURRENT to see the current trending (Health Check).    Click on HISTORY to see the historical evolution of the trending.

For flat-field exposures, the halogen lamp is used to illuminate the spectrograph. They are usually measured during daytime. Three health check settings with reference wavelengths 1090.4, 3218.6, and 4092.9 nm are defined and executed daily. Other settings are only measured when they are triggered by night-time observations.

On flat fields measured befor June 2009, only the central ~400 pixels (in Y direction) are illuminated on the detector because of the (short) length of the slit. CRIRES flat fields significantly vary for different settings and detectors. There are also several artefacts that are typical for specific settings. For reference wavelengths below about 1500 nm, the intermediate slit vignets parts of each spectroscopic order so that the outer regions of detectors 1 and 4 are not (well) illuminated. A strong gradient is present in dispersion direction (i.e. in X direction) and there is sometimes also contamination from adjacent orders.

For high Echelle orders, an optical ghost can be present on one detector. It is the result of a reflection from the detector to the grating.

FLAT frame. Example for 1090.4nm reference wavelength, detector #1. Dispersion is in X direction

Example for 1090.4 nm reference wavelength, detector #2, with an optical ghost

Example with full illumination (3218.6 nm, detector #3, June 2009 and later)

FLAT frame. Example for 1090.4nm reference wavelength, detector #3. Reduced slit length from 23 April to 11 June 2008

QC1 parameters for CRIRES flat-field exposures are measured for each detector array separately.

QC1 parameters

Trending

For trending of flat field QC1 parameters, the daily health check settings with reference wavelengths of 1090.4, 3218.6, and 4302.7 nm are used. The flat field flux and the master rms measure the stability of the lamp, of the lamp shutter, of the positioning of the pre-dispersing prism, and of the intermediate slit. Because of the current instabilities for the intermediate slit, it has been decided to only trend flux and rms for detector #3.

The number of bad pixels is trended for reference wavelengths 3218.6 nm.

History

January 2008: Reference wavelength of one daily HC setting changed from 4302.7 to 4092.9 nm.
23 April to 11 June 2008: Effective slit length is only 12 arcsec, which is about 200 pixels.
June 2009: detectors are fully illuminated
28 May 2010 until mid July 2010: variable slit width along length of slit; rms of flats increased