mirror sites:
PL (internal link)
HQ
[?]
Quality Control and
Data Processing
|
 |
XSHOOTER: Calibration recipes
DPR.CATG = CALIB, DPR.TYPE = BIAS,DETCHECK, FLAT,LINEARITY,DETCHAR
The detmon recipes for detector monitoring is a generic pipeline recipe to standardize the monitoring of science detectors of VLT optical and near infrared detectors. It is a technical calibration; products are not used for the processing of science data.
For the UVB-arm and VIS arm, equipped with optical CCDs, five bias frames
and a set of imaging flat pairs with increasing exposure time are acquired to cover the dynamic range of the detectors.
The detmon recipes detmon_opt and detmon_nir determine the deviation from linearity at a configurable reference count level and used the photon transfer curve to retrieve the gain in a very accurate way. The recipe measures, non-linearity and gain.
BIAS
DPR.CATG = CALIB, DPR.TYPE = BIAS
Bias frames are measured to monitor the status of the CCD. They come in stacks of 5 raw frames. They are routinely measured every night when XSHOOTER is operational, in the read modes "low gain" and "high gain" and different binning. They are processed by the pipeline into a MASTER_BIAS. They are scored and quality-checked by QC Garching.
The pipeline recipe xsh_mbias processes XSHOOTER UVB-arm and VIS-arm BIAS frames. These are combined and median-stacked.
The pipeline measures median values, read noise and global structure in the master BIAS and in the first raw frame.
DARK
DPR.CATG = CALIB, DPR.TYPE = DARK
Dark frames are measured to monitor the status of the VIS-arm and UVB-arm optical CCDs and the NIR-arm detector.
They come in stacks of 3 raw frames in the optical, each with 3600 sec integration time. They are taken
about monthly.
The pipeline recipe xsh_mdark processes XSHOOTER DARK frames. These are combined and median-stacked.
The pipeline recipe xsh_dark measures median values and dark current in the master DARK frame.
FMTCHK
DPR.CATG = CALIB, DPR.TYPE = LAMP,FMTCHK, DPR.TECH=ECHELLE,PINHOLE
Format check frames are taken regularly (every ~3 days) together with the order definition and the wave/distortion calibration. The 1-pinhole arc line Echelle spectrum is used to determine an initial guess of the Echelle spectrum format.
The recipe xsh_predict uses the arc line spectrum, the physical model and a subset of arc lines to fit the physical model to the arc line spectrum.
The number of found arc lines, the maximum gaps between arc lines and the number of found orders is checked for. Furthermore each arc line has an residual in x and y from the best model fit. The residual extrema are monitored.
ORDER
DPR.CATG = CALIB, DPR.TYPE = LAMP,ORDERDEF, DPR.TECH=ECHELLE,PINHOLE
Order defintion frames are taken regularly (every ~3 days) together with the format check and the wave/distortion calibration. The 1-pinhole flat lamp Echelle spectrum is used to determine the position of the orders
The recipe xsh_orderdef uses the flat lamp spectrum and the physical model to fit the physical model.
The number of found orders is monitored
WAVE
DPR.CATG = CALIB, DPR.TYPE = LAMP,WAVE, DPR.TECH=ECHELLE,MULTI-PINHOLE
The 9-pinhole arc frames are taken regularly (every ~3 days) together with the format check and the order defintion calibration. The 9-pinhole arc line Echelle spectrum is used to determine the 2D transformation from the Echelle spectrum (with tilted arc lines !) into a cartesian grid.
The recipe xsh_2dmap uses the 9-pinhole arc line spectrum, the physical model and arc lines from a catalogue to fit the physical model.
The number of found arc lines, and the number of found orders is monitored. Furthermore each arc line has an residual in x and y from the best model fit. The residual extrema are monitored.
FLAT
DPR.CATG = CALIB, DPR.TYPE = LAMP,FLAT, DPR.TECH=ECHELLE,SLIT or ECHELLE,IFU
The SLIT and FU flat fields are used to correct the Echelle blaze and the fixed pattern noise as instrumental effects in science spectra and standard star spectra. The pipeline recipe xsh_mflat corrects for the inter order background. Saturated pixel are excluded in the stacking routine.
The lamp flux itself and the counts in the flat frames is checked for, Furthermore the flux stability within the five raw flats and the gradient of the slit function. For technical IFU flats, the relative slice illumination is monitored, to draw conclusions on the position of the atmospheric dispersion corrector (ADC) optical elements and the impact of the ambient temperature and humidity on the Echelle optics.
ARC
DPR.CATG = CALIB, DPR.TYPE = LAMP,WAVE, DPR.TECH=ECHELLE,IFU, ECHELLE,SLIT
The spectral resolution cannot retrieved from the 9-pinhole arc calibrations. Either the sky lines embedded in the science frames have to be used (There is only one sky line in the UVB arm and in the red part of the NIR-arm. the brightness of the sky lines depends on the exposure time, which tuned for the science spectrum) or arc lamp spectra with the same SLIT (or IFU) as the science spectra has to be used. The latter is used here. The recipe xsh_wavecal fits the physical model to the arc line (SLIT (or IFU) spectrum and retrieves in addition the spectral resolution.
The spectral resolution and the number of found arc lines is monitored. Furthermore the difference between the 9-pinhole physical model fit and the SLIT (or IFU) physical model fit is monitored.
FLEX
DPR.CATG = CALIB, DPR.TYPE = LAMP,AFC, DPR.TECH=ECHELLE
The spectra of any night time exposure acquired at different telescope pointings and rotator angles are affect by different mechanical flexure, while day-time calibrations are always taken in the calibration position of the telescope and the instrument. To align these differences in a first order (shifts of the Echelle format), a short exposure 1-pinhole arc line spectrum is acquired as part of the acquisition template. The pipeline recipe xsh_flexcomp uses a small subset of arc lines and fits the physical model of the AFC frames to determine a shift with subpixel variance which is applied to the science exposure to align the spectral format to that of the day-time calibrations to optimize the wavelength solution.
The offset values are stored but not monitored. The offsets are more a property of the individual science exposure and not an instrument quality.
FLUX.STD
DPR.CATG = CALIB, DPR.TYPE = STD,FLUX, STD,SKY , DPR.TECH=ECHELLE,SLIT|IFU,STARE|NOD
The XSHOOTER calibration plan knows six individual spectrophotometric standard stars to be used to derive the efficiency of the instrument and the response function. The efficiency is a technical calibration to measure the throughput per wavelength and the response function is used to flux calibrate science spectra and telluric standard stars.
In SLIT mode the recipe xsh_respon_slit_nod processes in a first step the star in the same way as a
science spectrum. In a second step, the spectrum of model spectrum
of the star is aligned to observed spectrum of the spectrophotometric
standard star. The scaling function is the response function.
The efficiency at a certain refrence wavelength is trended. The spectral gradient of the response function is monitored.
TELL.STD
DPR.CATG = CALIB, DPR.TYPE = STD,TELLURIC, DPR.TECH=ECHELLE,SLIT|IFU,NOD|STARE
Science spectra from ground-based telescopes contain signatures of the
earth atmosphere, the so-called telluric absorption lines. The VIS-arm
and the NIR-arm are affected, while the contribution of the earth
atmosphere in the UVB-arm wavelength range is negligible.
For this reason brigh and fast rotating B-type stars with a flat continuum as 'screen'
for the telluric features or solar analogs (G-Type stars) are acquired. The pipeline recipe xsh_scired_slit_nod processes the telluric standard stars in the same way as science spectra. The resulting 1D spectrum can be used to disentangle the telluric features from the stellar features to construct the telluric spectru.
No Checks.
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 |
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||