Calibration data for VIMOS are taken for two purposes:

• assess the instrument status
• reduce science data

Generally VIMOS calibration data are taken as daytime calibrations. Given the mechanical instability of the instrument also nighttime calibrations are taken routinely in IFU mode and on request of the user in MOS mode. Nighttime calibration are obtained as part of the Observing Block which generates the SCIENCE data ("attached calibrations").

The calibration data taken obtained in IMAGING, MOS and IFU modes are processed by QC Garching to obtain calibration products. For imaging the data reduction is pipeline supported for all filters. For spectroscopy the pipeline reduction is supported for the following GRISM + Order Sorting Filter combinations:

• LR_red + OS-red
• LR_blue + OS-blue
• MR + GG475
• HR_orange + GG435
• HR_red + GG475
• HR_blue + None

The calibration products come as

• calibration product fits file frames (e.g. bias or flat field frames)
• calibration product fits tables (e.g. dispersion tables)

The following types of raw calibration data exist for the VIMOS IMAGING mode

frame DPR TYPE Purpose BIAS BIAS detector status, bias level, RON - DARK DARK dark current - TWILIGHT FLAT FLAT,SKY fixed pattern noise - SCREEN FLAT FLAT,LAMP gain, bad pixel map, lamp efficiency - PHOTOMETRY STD standard stars for photometric zeropoints -

The following types of raw calibration data exist for the VIMOS MOS and IFU modes

Notes : biases for imaging and for spectroscopy differ by their read-out mode.

Recipes and products

The following VIMOS calibration products are created from raw calibration files (click here for a complete overview of calibration files and recipes):

raw frame(s) recipe description product(s) BIAS vmBias create a master bias from set of input raw frames MASTER_BIAS DARK vmDark create a master dark from set of input raw frames MASTER_DARK TWILIGHT FLAT vmImFlatSky create a master twilight flat from set of input raw images MASTER FLAT FRAME SCREEN FLAT vmImFlatScreen vmDet create a master screen flat from set of input raw images - create bad pixel map and compute gain factor MASTER FLAT FRAME, BAD PIXEL MAP PHOTOMETRY vmImObsStare vmImCalOpt reduce standard star images and obtain photometric zeropoint of the night REDUCED STANDARD IMAGE, ZEROPOINT TABLE MOS FLAT vmSpFlat create a master flat from set of input flats MASTER FLAT FRAME MOS ARC vmSpCalDisp determine inverse dispersion relation INVERSE DISPERSION TABLE MOS SPECPHOTOMETRY vmSpCalPhot obtain the response function (SPECTROPHOTOMETRIC TABLE)* IFU FLAT vmifucalib determine inverse dispersion relation, fiber relative transmission, fiber tracing INVERSE DISPERSION TABLE TRANSMISSION TABLE TRACING TABLE EXTRACTED FLAT FIELD IFU ARC vmifucalib determine inverse dispersion relation, fiber relative transmission, fiber tracing INVERSE DISPERSION TABLE TRANSMISSION TABLE TRACING TABLE EXTRACTED FLAT FIELD IFU SPECTROPHOTOMETRY vmifustandard reduce spectrophotometric standard frames. The determination of the spectral response curve is not yet pipeline supported. TOTAL STD SPECTRUM EXTRACTED FIBER SPECTRA SKY SPECTRUM

* not yet pipeline supported

Association rules

The creation of calibration product follows the association rules.

Naming scheme

After production and certification, the calibration products are renamed after a scheme which includes type, creation data and relevant VIMOS setting. .

Like for all astronomical data, the reduction of VIMOS calibration frames requires a cascading scheme where the mutual dependencies of products and raw frames have to be respected. Master Biases can be produced from raw files only, but all the other products require the prior generation of other calibration products. The proper sequence of all these production steps is called the calibration cascade.

Within that cascade, all products are checked with respect to their quality and their relationship in time. This means e.g. that a master flat is not only generated using an arbitrary quality-checked Master Bias, but that specific table is chosen which at the moment of processing is closest in time . For the IFU mode, and when a NighCalib template is available, in addition to the closest in time rule, the calibration tables are selected also on the basis of the OBS ID keyword.

All products created by QC Garching follow the calibration cascade.

VIMOS Pipeline problems are documented under on the ServiceMode page.