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GIRAFFE: Grating stability
Temperature | Grating motions in X and Y | Correlation of shifts with temperature

 
HC PLOTS
Grating stability
QC1 database (advanced users): browse | plot

A set of frames is measured daily to monitor the stability of the gratings and of the fiber system. These frames carry the DPR TYPE SIMLAMP,TAL (TAL = thorium-argon lamp) and are created by the arclamp of the simultaneous calibration unit. The arc lamp is used to illuminate the simultaneous calibration fibres. The signal is correlated both in X (cross-disperion) and Y (dispersion) against a reference frame. There is a set of six such health check measurements, one (using the LR grating) for each slit system (Medusa1 and 2, IFU1 and 2, Argus), plus one for the HR grating and the Medusa1 slit system.

The data are also used to monitor the simlamp efficiency.

SIMLAMP,TAL frame (closeup). There are five simultaneous calibration fibres, illuminated by the simultaneous arclamp.


Temperature
Temperature | Grating motions in X and Y | Correlation of shifts with temperature

The GIRAFFE gratings have some minor thermal motions, and occasional non-thermal jumps. To control the thermal motions, the temperature sensor TEMP53 is monitored here, located on top of the grating table close to the grating.

QC1_parameters

FITS key QC1 database: table, name definition class* HC_plot** more docu
INS.TEMP53 giraffe_simlamp..ins_temp53_val temperature (sensor 53) in degree C ENG
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter
**There might be more than one, always check the link 'HC'.

Trending

As a comparison evalue, the temperature TEMP53 is plotted in box 1 and repeated in box 4 of the trending plot.

Scoring&thresholds Temperature

No scoring done.

History

Not applicable.

Algorithm Temperature

Not applicable.


Grating motions in X and Y
Temperature | Grating motions in X and Y | Correlation of shifts with temperature

Each of the Health Check data is correlated in X and Y to a reference frame. The set of reference frames is arbitrarily taken from date 2003-07-24. The difference (X_new - X_ref) is plotted vs. time. The same is done for the Y (dispersion) direction.

QC1_parameters

FITS key QC1 database: table, name definition class* HC_plot** more docu
[calculated by QC procedure] giraffe_simlamp..mean_xdiff average difference of selected line Y position against reference frame [pix]HC
[calculated by QC procedure] giraffe_simlamp..mean_ydiff average difference of selected line X position against reference frame [pix]HC
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter
**There might be more than one, always check the link 'HC'.

Trending

Boxes 2 and 3 of the trending plot display the X motions of the HR and LR grating (selected is the Medusa1 frame), boxes 5 and 6 the Y motions. Box 4 repeats the temperature record from box 1 for comparison.

Stability trending plot, panel 1 . On top there is the trending of the temperature (in degree Celsius), and below are the plots for the shift in X direction, both for the HR and the LR grating. The temperature sensor selected is TEMP53 ('surface table temperature top').

A similar column is plotted for the Y shifts (panel 2).

Scoring&thresholds Grating motions in X and Y

The scoring thresholds in plots #2 and #5 (for the HR grating) and #3 and #6 (LR) are set such as to indicate a) a sudden, non-thermal jump, or b) a slow drift towards critical values for the position of the gratings (critical because the pipeline then might loose parts of the fibre signal). The positions have no particular physical meaning but are relative and based on historical behaviour.

History

The incremental grating motions due to temperature are well visible in the correlation plots #7-10 (see below). The correlation slope is very stable over time, indicating clearly non-thermal motions (interventions, earthquakes).

Algorithm Grating motions in X and Y

The cross-correlation between the actual file and fixed reference is calculated in X and Y.


Correlation of shifts with temperature
Temperature | Grating motions in X and Y | Correlation of shifts with temperature

The third panel shows the shifts in X and Y versus temperature TEMP53. For both directions, there is essentially the same (anti-) correlation with temperature.

Correlation plot. Boxes 7 and 8 show the shift of the grating in X direction, in pixels, versus the temperature drifts (TEMP53 as above). X-axis: grating shifts in X; Y-axis: TEMP53 in degrees Celsius.

Boxes 9 and 10 display the same for the Y shifts.

Note that the Giraffe gratings occasionally show sudden non-thermal shifts. These are detected in the trending plot as corresponding shift of the correlation pattern in X direction.

QC1_parameters

FITS key QC1 database: table, name definition class* HC_plot** more docu
[calculated by QC procedure] giraffe_simlamp..mean_xdiff average difference of selected line Y position against reference frame [pix]HC
[calculated by QC procedure] giraffe_simlamp..mean_ydiff average difference of selected line X position against reference frame [pix]HC
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter
**There might be more than one, always check the link 'HC'.

Trending

Same as above.

Scoring&thresholds Correlation of shifts with temperature

The scoring thresholds in plots #2 and #5 (for the HR grating) and #3 and #6 (LR) are set such as to indicate a) a sudden, non-thermal jump, or b) a slow drift towards critical values for the position of the gratings (critical because the pipeline then might loose parts of the fibre signal). The positions have no particular physical meaning but are relative and based on historical behaviour.

History

Date event
2007-11-14 earthquake; non-thermal jump of HR grating in X (+1) and Y (+2) pixels
2011-03-14 earthquake, non-thermal jump in Y direction; adjusted backto the old values on 2011-04-01; no science files affected
2011-06-10 earthquake, non-thermal jump in X and Y direction; adjusted back to the old values on 2011-06-22
2011-06-27 earthquake, non-thermal jump in X; adjusted back on 2011-06-30
2015-11-27 earthquake, non-thermal jump of HR in X by +8 px, LR in Y by more than 1 px; adjusted back begin of 2015 Dec; required new reference dispersion solutions for Medusa2

Algorithm Correlation of shifts with temperature

Not applicable.


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