QC PLOTS
	CURRENT	HISTORY
wavelength_calibration
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The wavelength day calibration consists in using the MIDI heated blackscreen and taking 3 exposures through different narrow-band filters [NeII], [SIV] and [ArIII] (having central wavelengths accurately measured in the laboratory by the manufacturer). An extra exposure is taken through a polycarbonic foil that has several absorption lines in its N-band spectrum. Exposures without filters and with closed shutter are also taken to process the exposures with filters. From the spectra obtained through the filters a fit of the lambda(X) function is performed. The procedure is performed for each setup (PRISM or GRISM, and SCI_PHOT or HIGH_SENS). We monitor here the stability of the dispersion by plotting the wavelength of a spectral channel given by the lambda(X) function computed by the reduction of the calibration data. The selected spectral channels corresponds to the expected central wavelength of the three narrow-band filters.  

The spectral dispersion is performed horizontally on the detector. There is a relationship between the x-coordinate of an illuminated pixel and the wavelength. This can be written: lambda(X)=C2X^2 + C1X + C0, where X is the pixel position. The coefficients C0, C1, C2 have to be determined by the calibration procedure.

There is one calibration per instrument setup: High-sens and sci-phot and per dispersive element: prism and grism.

The results are given for each region (window) on the detector (4 in the case of sci-phot, 2in the case of high_sens). A channel refers to a column in the detector window.

QC1 parameters

For each of the instrument mode: SCI_PHOT, HIGH_SENS and each dispersive element : PRISM and GRISM and for different filters [NeII], [SIV], [ArIII] and a foil: the wavelength is measured on a fixed channel.

• prism mode (QC1 database table midi_wave, columns ArIII/NeII/SIV_r1/2/3/4 where ins_disp = prism), where r1, r2, r3 and r4 correspond to the 4 windows which could be recorded on the detector.
• grism mode (QC1 database table midi_wave, columns ArIII/NeII/SIV_r1/2/3/4 where ins_disp = grism) where r1, r2, r3 and r4 correspond to the 4 windows which could be recorded on the detector.

Trending

Filter SIV in the triple pinhole setting recorded for window 2

Foil in the triple pinhole setting recorded for window 2