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HAWK-I:
calibration data

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general HAWK-I

CALIBRATION DATA: GENERAL

Calibration data are taken for two purposes:

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

HAWK-I calibration data are mostly taken as daytime calibrations. Flux standard stars and nasmyth screen flats are taken, as part of the calibration plan, for Argus data.

On request by the user, also nighttime calibrations can be obtained as part of the Observing Block which generates the SCIENCE data ("attached calibrations"). Furthermore simultaneous arclamp calibration is available, upon request, by feeding some fibres with light from the simultaneous calibration unit (SCIENCE data taken in SimCal mode).

TYPES OF RAW CALIBRATION DATA

Find information about the HAWK-I data format, and the detector here.

The following calibration data are taken as part of the daily HAWK-I calibration plan. The data types are identified by the DPR TYPE keyword in the FITS headers.

frame DPR.CATG DPR.TYPE DPR.TECH purpose N*
DARK CALIB DARK IMAGE detector status, dark level, readout noise
>3
TWILIGHT FLAT CALIB FLAT
IMAGE Small scale pixel-pixel efficiency variation correction
>3
STD star CALIB STD IMAGE Zero-point monitoring, photometric calibration of SCIENCE data 4

* N: DARK and FLAT pipeline recipes require AT LEAST 3 frames. The exact number of DARKs acquired for each setting used during a night is controlled by the calibration plan. The exact number of FLATs acquired for each filter varies; ideally the full dynamic range of the chips should be evenly sampled with at least 10 frames. To be reduced by the STD pipeline recipe, the template must make exactly FOUR observations.

There is only ONE readout mode for HAWK-I, 1x1 binning.

HAWK-I has no internal calibration lamp system, therefore only twilight flats are available. There are NO Dome- or Internal- FLATS usefulfor SCIENCE processing

CALIBRATION PRODUCTS

Complete overview of calibration files and recipes

Raw frame(s) recipe description
product(s)
DARK hawk_img_dark create a master dark, bad pixel mask for hot pixels and compute some basic statistics from set of input raw frames DARK_IM, BPM_HOT, DARK_STATS
FLAT hawki_img_flat Small scale pixel-pixel efficiency variation correction, master flat, COLD and Combined bad pixel masks, compute basic stats from set of input raw frames FLAT_IM, BPM_COLD, BPM, FLAT_STATS
STANDARD STAR hawki_img_zpoint Zero-Point monitoring ZPOINT_IMA, ZPOINT_RES, ZPOINT_STATS

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 HAWK-I 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 flat field is not only generated using an arbitrary quality-checked HOT bad pixel map solution, but that specific bad pixel map is chosen which is closest in time.

All products created by DFO Garching follow the calibration cascade. In contrast, Paranal-processed science do not use any calibrations.
STATIC CALIBRATION TABLES

The following static calibration tables (the ones not being regularly processed from raw calibration data) are useful for HAWK-I data processing:

  • the standard star catalogue
  • the distortion map

They come as FITS tables (extension fits). They are part of the SM delivery for HAWK-I data.

TABLE NAME PRO_CATG PURPOSE
HI_GSSC_081103A_stdstars_cat.fits STDSTARS_CATS Table of standard star names, coordinates, spectral type, and JHKsY magnitudes, more information about STDSTAR_CATS is here
HI_GDIS_081012A_distortion_map.fits DISTORTION Distortion map


 
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