QC PLOTS
	CURRENT	HISTORY
intensity		not implemented
flux calibration		not implemented
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.

Since 2006 the ISAAC calibration plan includes the observation of bright flux standard stars. The standards are taken with setup SW-arm, LR-grating and mask_L2 meaning slit less spectroscopy. The observations are done usually 6 times a year in all four wavelength filters/wavelength bands: SZ,J, SH, and SK. Only eight stars have been selected out of the operational catalog of telluric standards for this calibration.The flux standard star observations are processed by the pipeline. In a first part the two raw spectra are co-added and extracted in the same manner as for science spectroscopy or telluric standard stars. As there are no sky emission lines in slit less spectroscopy day time arc-lamp calibrations are used for the wavelength calibration. Generally if the flux standard is used to calibrate science spectra it is advised to flat field the flux standard with the same flat as the science spectrum in order to cancel out the lamp spectrum and other low order features. Within the QC process the flux standards are not used to calibrate science spectra; the flux standard spectra are not flat fielded. The high order fixed pattern noise (= pixel to pixel gain variations) is not reduced but the spectra are clean from lamp features. In as second part the spectra are compared with stellar spectra for spectrophotometric calibrations.

The final pipeline product table consisting of three columns: for wavelength, source spectrum and residual sky spectrum as the product spectra of science spectra and telluric standard stars. In addition the product table for flux standards contains two more columns, one for the efficiency as function of wavelength and one for the conversion (from ADU in erg/cm/cm/sec/Ang) as a function of wavelength.

The conversion as monitored as part of the QC process is a pure technical calibration and is not suitable to be used directly to calibrate science spectra delivered by the pipeline, as the science spectra are flat fielded but the flux standards not.

Table of the 8 monthly taken ISAAC flux calibration standard stars.

QC1 parameters

parameter	QC1 database: table, name	procedure
wavelength calibration method	isaac_flux, qc_wl_method	- the wavelength calibration method finally used (arc lines, sky lines or physical model). arc lines is the operational default.
central wavelength	isaac_flux, qc_wlen	- the central wavelength in micron, derived from the dispersion solution
dispersion solution	isaac_flux, qc_dispco1, qc_dospco2, qc_dispco3, qc_dispco4	- the wavelength calibration polynomial coefficients
fit quality	isaac_flux, qc_xcorr	- the wavelength calibration correlation coefficient
arc line results	isaac_flux, arc_...	- the wavelength calibration results from the associated arc line calibration product
grating offset	isaac_flux, qc_SA_offset	- grating offset between associated arc product and flux standard star ( = ( qc_wlen(telluric) minus qc_wlen(arc) ) in pixel

QC1 parameters

QC1 parameters

Trending

Not implemented

We plot the efficiency as a function of wavelength. The efficiency (measured flux in units of real flux) is fit by a linear function (SZ,SH, SK), but for the J band by a quadratic function. The wavelength intervals for the fit are:

• SZ [ 1.04 : 1.10 ] mu
• J [ 1.15 : 1.32 ] mu
• SH [ 1.60 : 1.75 ] mu
• SK [ 2.10 : 2.30 ] mu

QC1 parameters

Trending