Quality Control and
Data Processing

HC PLOTS
Reference wavelength
OPD fit
Argon lamp

Wavelength calibrations are measured during daytime as part of the P2VM calibration sequence using a simulated star spectrum from the calibration unit, with one of the grisms inserted (low, medium, or high resolution), and with the Wollaston prism either inserted (split) or not inserted (combined polarimetry). All four inputs are simultaneously opened.

Wavelength calibration. Medium resolution, combined polarimetry.

Additional calibrations are measured weekly with the Argon lamp. These are not used for calibrating science data but to monitor the instrument stability.

Argon lamp exposure. Medium resolution, combined polarimetry.

QC1_parameters

The pipeline calculates a wavelength map which matches detector pixels with wavelengths.

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
QC.REFPOS1.FT1	gravity_p2vm..refpos1_ft1	position (pixel) of reference wavelength on detector	HC		[docuSys coming]
QC.REFPOS1.FT24	gravity_p2vm..refpos1_ft24	position (pixel) of reference wavelength on detector	HC		[docuSys coming]
QC.REFPOS1.FT48	gravity_p2vm..refpos1_ft48	position (pixel) of reference wavelength on detector	HC		[docuSys coming]
QC.REFPOS1.SC1	gravity_p2vm..refpos1_sc1	position (pixel) of reference wavelength on detector	HC		[docuSys coming]
QC.REFPOS1.SC24	gravity_p2vm..refpos1_sc24	position (pixel) of reference wavelength on detector	HC		[docuSys coming]
QC.REFPOS1.SC48	gravity_p2vm..refpos1_sc48	position (pixel) of reference wavelength on detector	HC		[docuSys coming]
QC.REFPOS2.FT1	gravity_p2vm..refpos2_ft1	position (pixel) of reference wavelength on detector	HC		[docuSys coming]
QC.REFPOS2.FT24	gravity_p2vm..refpos2_ft24	position (pixel) of reference wavelength on detector	HC		[docuSys coming]
QC.REFPOS2.FT48	gravity_p2vm..refpos2_ft48	position (pixel) of reference wavelength on detector	HC		[docuSys coming]
QC.REFPOS2.SC1	gravity_p2vm..refpos2_sc1	position (pixel) of reference wavelength on detector	HC		[docuSys coming]
QC.REFPOS2.SC24	gravity_p2vm..refpos2_sc24	position (pixel) of reference wavelength on detector	HC		[docuSys coming]
QC.REFPOS2.SC48	gravity_p2vm..refpos2_sc48	position (pixel) of reference wavelength on detector	HC		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

The positions of two reference wavelengths (2.099 and 2.314 microns) on the detectors are trended for the lowest spectrum on the detector.

Scoring&thresholds Wavelength solution

Scoring thresholds have been set up to median +/- 3sigma in May 2019. For the SC, this is +/- 0.1 pixels and for the FT +/-0.04 pixels, respectively. Only reference position 1 is scored since the other is highly correlated.

History

No particular events.

Algorithm Wavelength solution

refpos1: Position of the reference wavelength 1 (2.099 um) on the detector in the 1st (lowest) spectrum, for FT and SC, respectively. Same for the 24th and 48th (only for split polarimetry) spectrum.
refpos2: Position of the reference wavelength 2 (2.313 um) on the detector in the 1st (lowest) spectrum, for FT and SC, respectively. Same for the 24th and 48th (only for split polarimetry) spectrum.

QC1_parameters

The pipeline calculates the RMS of the fit: * SC + b * FT + c = MET.

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
QC.ABCRMS.WAVEFT	gravity_p2vm..metfit_rms_ft	RMS from fit of a * SC - b * FT & c = MET	CAL		[docuSys coming]
QC.ABCRMS.WAVESC	gravity_p2vm..metfit_rms_sc	RMS from fit of a * SC - b * FT & c = MET	CAL		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

The RMS of the fit residuals is trended for FT and SC and for the six combinations of resolution and polarimetry mode.

Scoring&thresholds OPD fit residuals

The upper threshold for a good fit has been set to 100nm, as recommended by the consortium.

History

Introduced in August 2019.

Algorithm OPD fit residuals

Residuals of the fit between metrology, phase observed on the science camera, and phase observed on the fringe tracker: a * SC + b * FT + c = MET. The sum of these three OPDs should be constant. If it is not the case then the fit will show high residuals.

QC1_parameters

The pipeline calculates a wavelength solution from ten Argon lines on the SC detector and compares the result from the dispersion solution to the catalogue wavelengths.

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
none	gravity_wavelamp..wdiff1	difference between actual and theoretical wavelength (in microns)	HC		[docuSys coming]
none	gravity_wavelamp..disp_rms	RMS of the wavelength differences from the dispersion solution	HC		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

The QC1 parameters are trended for medium resolution and combined polarimetry (which is the set-up used for weekly monitoring).

Scoring&thresholds Argon lamp

Scoring thresholds have been set up empirically and only for dispersion RMS.

History

No particular events.

Algorithm Argon lamp

wdiff1: Difference between the catalogue wavelength and the wavelength according to the dispersion solution for Argon line 1. Same for lines 2 to 10.
disp_rms: Standard deviation of wdiff1, ..., wdiff10.