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UVES:
calibration data
 

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CALIBRATION DATA: GENERAL

Calibration data are taken for two purposes:

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

Generally UVES calibration data are taken as daytime calibrations. On request by the user, also nighttime calibrations can be obtained as part of the Observing Block which generates the SCIENCE data ("attached calibrations").

All calibration data taken in UVES standard settings are processed by the QC group to obtain calibration solutions. These solutions come as

  • master calibration files (master BIAS, master FLAT),
  • calibration products like dispersion tables or standard star response files.
TYPES OF RAW CALIBRATION DATA


The following table contains an overview of the raw calibration files for the UVES echelle mode. The data types are identified with the DPR TYPE keyword of the fits headers.

frame DPR TYPE Purpose
typical number taken per night and setting
BIAS BIAS detector status, bias level
5
DARK DARK dark current
3 per month for monitoring
FORMAT CHECK LAMP,FMTCHK align spectral format to physical model
1
ORDER DEFINITION FLAT LAMP,ORDERDEF define position of orders and interorder background
1
WAVELENGTH CALIBRATION LAMP,WAVE dispersion relation
1
ECHELLE FLAT LAMP,FLAT fix-pattern noise, fringing, slit function, blaze function
5
ECHELLE DEUTERIUM FLAT LAMP,DFLAT same as ECHELLE FLAT, but higher sensitivity in the extreme blue (346 nm) 5
ECHELLE ABSORPTION-CELL FLAT LAMP,IFLAT ECHELLE FLAT with the Iodine absorption cell switched on (setting RED 600 1x1) 5
STANDARD STAR EXPOSURE STD spectral response of telescope, instrument, detector; efficiency
1

FLATs are taken for each setting and slit width used for SCIENCE data.

Examples of raw UVES frames, FITS headers, and some pipeline products are available from the UVES reference frames page.

For a complete overview of the data types and their dependencies, check the calibration cascade.

 

CALIBRATION PRODUCTS


Complete overview of calibration files and recipes

The following UVES calibration products are created from raw calibration files:

raw frame(s) recipe description
product(s)
BIAS [bias_th.gif 3K] uves_cal_mkmaster create a master bias from set of input raw frames
MASTER_BIAS
DARK uves_cal_mkmaster create a master dark from set of input raw frames
(MASTER_DARK)*
FORMAT CHECK [fmt_th1.gif, 2K] uves_cal_predict obtain first guess wavelength calibration solution
LINE_TABLE (guess), DRS_SETUP TABLE
ORDER DEFINITION FLAT [order_th.gif, 2K] uves_cal_orderpos define order table and background table
ORDER_TABLE, BACKGROUND_TABLE, DRS_SETUP_TABLE
WAVELENGTH CALIBRATION [wave_th.gif 3K] uves_cal_wavecal obtain wavelength calibration solution
LINE_TABLE_1/2/3, DRS_SETUP_TABLE
ECHELLE FLAT [flat_th.gif 2K] uves_cal_mkmaster create a master flat from set of input flats
MASTER_FLAT
STANDARD STAR EXPOSURE [std_th.gif 2K] uves_cal_response determine instrumental response, efficiency
RESPONSE, EFFICIENCY_TABLE

* for monitoring, taken once a month

If there are several sets of daytime calibration data, only one is processed. If there are one or several sets of night-time calibration data, they are all processed.

Naming scheme

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

Description of naming scheme

 

CALIBRATION CASCADE


The processing of UVES calibration frames requires a cascading scheme where the mutual dependencies of products and raw frames have to be respected. Some products (master bias, first guess line table) can be produced from raw files only, but most products require the prior generation of other calibration products. The proper sequence of all these production steps is called the calibration cascade (see also here).

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 order table, but that specific table is chosen which at the moment of processing is closest in time.

All products created by QC Garching respect the calibration cascade.

STATIC CALIBRATION TABLES


The following static calibration tables (not regularly updated) are used by the UVES pipeline:

The flux standard table contains tabulated fluxes for the flux standard stars in use for UVES.

They have been part of the data packages for UVES data, and they are also delivered through the calSelector archive service.

ACTUAL PROBLEMS AND ISSUES

Note that in the extreme blue setting (346 blue/di1/di2), two kinds of flats are measured: one with the usual flat field lamp (FF), one with a deuterium lamp (D). Both types of flats can be processed into master flats.