HAWKI pipeline:
CALIB recipes

DARK frames (hawki_dark_combine (new with v.2.0, was hawki_cal_dark))
DPR.CATG = CALIB, DPR.TYPE = DARK, DPR.TECH = IMAGE

Master DARK frame

Purpose. Dark exposures are obtained regularly to monitor the status of the detector array. They can also be used to subtract the dark current in science frames. Each dark stack consists of 10-15 raw frames. They are combined into one master dark product and quality-checked By QC Garching and occasionally on the mountain.

Recipe. The pipeline recipe hawki_dark_combine (new with pip. 2.0, was hawki_cal_dark) combines 10 raw darks by median-stacking.

QC checks. The pipeline measures median values, read noise and the standard deviation of the input frames.

Trending. Click here for trending results.

Products.

FLAT frames (hawki_twilight_flat_combine (new with pip. v.2.0, was hawki_cal_flat))

DPR.CATG = CALIB, DPR.TYPE = FLAT, DPR.TECH = IMAGE

Example of the master FLAT frame

Purpose. HAWK-I flat fields are measured on sky usually at the beginning of the night, at twilight. The clear skies as required for the calibration of SCIENCE data. HAWK-I instrument does not have an internal lamp. In the infrared, twilight flats are taken in a manner to sample a large flux range by integrating on the twilight sky as the sun sets or rises. Twilight flats are therefore, one of the most time critical calibrations, since of the narrow time window. This is also the reason why more operational related quality parameters like the covered flux range are monitored for twilight flat calibrations. They are used to determine the standard deviations of the pixel values of each detector.

Recipe. The pipeline recipe hawki_twilight_flat_combine (new with v.2.0, was hawki_cal_flat) operates on stack of frames. First, the recipe subtracts a master dark frame from each input raw flat. Then traces of the stars are removed (second pass) and the master flat is normalised by its median level. Bad pixels are defined as those pixels with values outside given thresholds in the normalised frames.

QC checks. The pipeline measures the mean flux of the input raw frame, the standard deviation of the product, and the total number of bad pixels.

Trending. The stability of the flats is trended here.

Products.

DETLIN frames (detmon_ir_lg)

DPR.CATG = CALIB; DPR.TYPE = DARK,DETCHEK; DPR.TECH = LINEARITY, LAMP or
DPR.CATG = CALIB; DPR.TYPE = FLAT,LAMP,DETCHECK; DPR.TECH = LINEARITY, LAMP

Purpose. A series of DARK and FLAT exposures with increasing DIT to measure non-linearity and gain.

Recipe. For the non-linearity determination, the pipeline recipe first subtracts from each flat frame the corresponding dark exposure with the same DIT. Then, for each pixel the function

ADU = A + B * DIT + C * DIT^2

is fit. The B coefficients basically reflect the unknown intensity of the flat-field lamp whereas deviations from linearity are measured via the C coefficients. The output of the recipe consists of 3 images for the A, B, and C coefficients, respectively, which are stored in one product (LINGAIN_COEFFS).

QC checks. The pipeline reports median values for the coefficients and an effective non-linearity correction at a given exposure level.

Trending. The effective non-linearity is trended here.

Products.

STD frames

DPR.CATG = CALIB, DPR.TYPE = STD, DPR.TECH = IMAGE

Example of the reduced STD frame

Purpose. HAWK-I standard star observations are taken each night the science observations are acquired. They are used to monitoring the overall instrument efficiency.

Recipe. Standard stars are processed by the recipe hawki_standard_process (new with v.2.0, was hawki_cal_zpoint). Each standard star OB obtains 1 set of standard star data in one filter comprised of four RAW data files, with the standard star placed at the center of the each detector sequentially. The Computed zeropoint, corrected for atmospheric extinction and the maximum counts in ADU in the standard star are monitored for each detector.

QC checks. Extinction corrected zeropoints, source peak value

Trending. The zeropints in different filters are trended here.

Products.