CALIBRATION DATA: GENERAL

Calibration data are taken for two purposes:

• to calibrate SCIENCE data
• to measure and control the instrumental status

ISAAC calibration data like darks, lamp flats and arc frames are mostly taken as daytime calibrations. Standard stars, startrace calibrations, and illumination correction calibrations are taken during night time; imaging sky flats are taken during twilight.

On request by the user, also nighttime calibrations, only spectroscopic flats and arc frames, can be obtained as part of the Observing Block which generates the SCIENCE data ("attached calibrations").

Find information about the ISAAC data format, spectral format and the detector here.

The following calibration data are taken as part of the daily ISAAC calibration plan for imaging modes. The data types are identified by the DPR TYPE keyword in the FITS headers.

The following types of calibration data exist for ISAAC spectroscopy modes:

Complete overview of calibration files and recipes

The following calibration data products are generated by the data reduction pipeline.
The dataproduct types are identified by the PRO CATG keyword in the FITS headers.

raw frame(s) description PRO CATG keyword of data products DARK create a master dark from set of input raw frames and calculates the RON MASTER_DARK TWILIGHT FLAT create a master twilight flat and checks detector odd-even column effect and structural noise and bad pixel MASTER_IMG_FLAT MASTER_BPM MASTER_IMG_FLAT_ERRMAP ILLUMINATION technical calibration to monitor throughput, spatially resolved in the field of view, in imaging mode ILLUM_FLUX ILLUM_FRAME ZEROPOINT obtain photometric zeropoint ZPOINT ZP_TAB SLIT IMAGE   technical calibration to a) monitor the grating position, b) slit position on the detector and C) the position of the objective SLIT_DESC SPECTROSCOPY FLAT create a master flat from set of input flats, correct slit function and structural noise MASTER_SP_FLAT ARC wavelength dispersion solution, optical distortion in x, spectral resolution ARC_CORRECT ARC_COEF LW_ARC_CORRECT LW_ARC_COEF STARTRACE optical distortion in y and model spectral curvature STAR_TRACE_POSI STAR_TRACE_SHAPE STAR_TRACE_COEF LW_STAR_TRACE_POSI LW_STAR_TRACE_SHAPE LW_STAR_TRACE_COEF LINEARITY determine non-linearity coefficients DETLIN_A DETLIN_B DETLIN_C DETLIN_Q TELLURIC STANDARD STAR provide a telluric absorption spectrum template SPEC_EXTRACTED SPECTRA_COMBINED SPECTROSCOPIC FLUX STANDARD   technical calibration to monitor throughput in spectroscopy mode SPEC_EXTRACTED SPECTRA_COMBINED

Naming scheme

After production and certification, the calibration products are renamed with a more user-friendly scheme which includes type, creation date and relevant setting parameters.

Description of naming scheme

CALIBRATION CASCADE

The processing of ISAAC calibration frames requires a cascaded scheme where the mutual dependencies of products and raw frames are respected. The proper sequence of all these production steps is called the calibration cascade. It is described here.

Within that cascade, all products are checked with respect to their quality and their relationship in time. This means e.g. that a dispersion solution is not only generated using an arbitrary quality-checked localization solution, but that specific solution is chosen which is closest in time.

All products created by QC Garching follow the calibration cascade. On contrary, Paranal-processed science data never use the up-to-date calibration products but standard solutions manufactured by QC Garching and possibly several months old.

STATIC CALIBRATION TABLES

The following static calibration tables (the ones not being regularly processed from raw calibration data) are required for ISAAC data processing:

• the sky OH emission line table
• the Argon emission line table
• the Xenom emission line table
• the photometric standard star table
• the spectral energy distribution table

They come as FITS binary tables. They are part of the SM delivery for ISAAC data.

The static tables can be downloaded as gzipped tar file here [440 kB, created in September 2007].

TABLE NAME PRO_CATG PURPOSE oh.fits CALPRO_OH_CATALOG wavelength calibration using sky OH emission lines ar.fits CALPRO_AR_CATALOG wavelength calibration using argon emission lines xe.fits CALPRO_XE_CATALOG wavelength calibration using xenon emission lines STDSTARS.fits STDSTARS_CAT catalog of photometric standard stars, used for photometric zeropoints and conversion function SEDS.fits SEDS spectral energy distributions of selected spectral types, used for flux calibration