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Quality Control and
Data Processing

CAL | HC | refs | QC
Trending & QC1
QC links:
SINFONI: distortion
Average of 32 slitlet distances (J,H,K,H+K together)
Average iof 32 slitlet distances (J,H,K,H+K separately)
Distortion shift in 4 quadrants and center of detector
Distortion coefficient C00
Distortion coefficient C01
Distortion coefficient C10
Distortion coefficient C11
Distortion coefficient C20
Distortion coefficient C02
Distortion coefficient C21
QC1 database (advanced users): browse | plot

Distortion frames are used to determine the spatial distortion on the SINFONI detector and determine the distances between the individual slitlets. This calibration is made once per month, as well as immediately following an intervention. It consists of about 75 FIBRE_NS frames, a FLAT_NS (a lamp-on/off pair), and a WAVE_NS (arc lamp on/off pair). Each fibre frame consists of an illuminated fibre imaged along each slitlet position and moved, from image to image, perpendicularly to the slices. When these frames are coadded they create uniformly illuminated slits across the full detector (see Figure below). The arc lamp frames are used to determine the positions of the edges of each slitlet. The distortions are only obtained at the 25 mas pixel scale. Due to the inherent stability of SINFONI, the distortions are only obtained once every 30 days.

The background-subtracted stack of 75 FIBRE_NS frames. The uniformly illuminated centers of each SINFONI slitlet is clearly visible. The slitlet numbering is shown at the bottom.

To make the effects of changing distortion coefficients more easily visible, the optical distortion is applied to five different positions on the detector. Shown as green dots, these positions are at pixels: (512,512), (512,1536), (1536,512), (1536,1536), and (1024,1024). This is trended in the distortion shifts.

Parameters trended


FITS key QC1 database: table, name definition class* HC_plot** more docu
QC.SL.DISTAVG sinfoni_dist..qc_sl_distavg optical distortion coefficient HC [docuSys coming]
QC.SL.DISTRMS sinfoni_dist..qc_sl_distrms scatter in slitlets distances HC [docuSys coming]
QC.XSHIFT.UL sinfoni_dist..qc_xshift_ul distortion in UL quad centerHC [docuSys coming]
QC.XSHIFT.UR sinfoni_dist..qc_xshift_ur distortion in UR quad centerHC [docuSys coming]
QC.XSHIFT.LL sinfoni_dist..qc_xshift_ll distortion in LL quad centerHC [docuSys coming]
QC.XSHIFT.LR sinfoni_dist..qc_xshift_lr distortion in LR quad centerHC [docuSys coming]
QC.XSHIFT.CC sinfoni_dist..qc_xshift_cc distortion in chip centerHC [docuSys coming]
QC.COEFF00 sinfoni_dist..qc_coeff_00 optical distortion coefficient HC [docuSys coming]
QC.COEFF10 sinfoni_dist..qc_coeff_10 optical distortion coefficient HC [docuSys coming]
QC.COEFF01 sinfoni_dist..qc_coeff_01 optical distortion coefficient HC [docuSys coming]
QC.COEFF11 sinfoni_dist..qc_coeff_11 optical distortion coefficient HC [docuSys coming]
QC.COEFF20 sinfoni_dist..qc_coeff_20 optical distortion coefficient HC [docuSys coming]
QC.COEFF02 sinfoni_dist..qc_coeff_02 optical distortion coefficient HC [docuSys coming]
QC.COEFF21 sinfoni_dist..qc_coeff_21 optical distortion coefficient HC [docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter
**There might be more than one.


QC report for DISTORTION frames.

The QC report for the DISTORTION includes:

  • UL: the distance (in pixels) between adjacent slitlets. The 31 distances between slitlets in the current distortion are plotted as blue dots, with their median (blue line) and +/- 1 sigma range (shaded green area) shown. The red dotted line displays the median slitlet distance of a reference distortion.
  • UR: the distortion coefficients applied to 5 positions on the detector: the chip center and its four quadrants. Black circles depict the nominal values [(512, 512), (1536, 512), (1024, 1024), (512, 1536), (1536, 1536)], the current distortion is shown with blue squares, and the reference distortion is shown as red squares. The difference between the current distortion and the nominal values are printed to the right of the figure (in pixel offsets).
  • LL: an image of the current distortion.
  • LR: an image of the difference between the reference and the current distortion.

    Scoring&thresholds Parameters trended

    Average distances between the 32 slitlets

    Scoring thresholds have been set rather losely .


    Based on the inherent stability of the SINFONI optical path, the measurement of the optical distortion has a validity of 20 days. The only potential issue is that the distortion calibration template will, occasionally, produce an incomplete set of frames. This can include either missing FLAT_NS frames, missing FIBRE_NS frames, or frames without flux from the fibre. In these cases the distortion calibration will be repeated when this problem is detected by Garching, QC.

    Algorithm Parameters trended

    The ~75 frames consisting of a single fibre light source moved perpendicular to the 32 pseudo slit slices are coadded to produce an image with all slits illuminated. The intensity maximum of each column is determined and a least-squares Gaussian fit is performed to locate the fibre's flux and locate the slitlet center. The relative distance between each trace is averagedi(qc.sl.distavg and rms). The distortions are done at the 25 mas pixel scale. The optimal value is 64 pixels.

    The distortion function characterizes the curvature of the 32 spectral traces on the coadded fibre images. For each slitlet the centroids of the fibre traces are detected and traced along the curved spectra. Two 2-d numerical grids are constructed; one on the distorted fibre positions and the other on the optimal expected fibre positions. The above 2-d polynomial function is fit to transform the positions from the raw to undistorted coordinates.
    The two dimensional polynomial fit to characterize the curvature of the 32 spectral slitlet traces is given by:

    distortion(x,y) = C00 + C10*x + C01*y + C11*x*y + C20*x2 + C02*y2 + C21*x2*y + C12*x*y2
    Since the distortion coefficients are relatively abstract, the optical distortion is also computed at five positions on the detector.

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