QC PLOTS
	CURRENT	HISTORY
Daily Health Checks (only plate 1 data are monitored):
MOS FMTCHK GratPos PhysM 520 P1
580 P1
860 P1
QC1 uves_fib_fmtchk database (advanced users): browse | plot
Click on CURRENT to see the last trending (Health Check).    Click on HISTORY to see the historical evolution of the trending.

This tutorial provides information for the UVES grating position. It is based on the measurement of QC1 parameters of MOS FORMAT CHECK calibration data. There are three sets of MOS FORMAT CHECK data, 1 set in each of the three wavelength settings available in MOS mode (520.0, 580.0 and 860.0nm), each set comprising a single RAW frame. Only one of the OzPoz plates is used (Plate-1).

The recipe performs a comparison between the detected line positions and the physical model. This is useful to verify the precision of physical model prediction and instrument spectral format stability.

• difference of X positions to physical model (QC1 database table uves_fib_fmtchk, column mean_dx, product keyword QC.MODEL.DIFFXAVG)
  
• difference of Y positions to physical model (QC1 database table uves_fib_fmtchk, column mean_dy, product keyword QC.MODEL.DIFFYAVG)
  
• number of lines selected (QC1 database table uves_fib_fmtchk, column nlin_sel, product keyword QC.MODEL.NLINSEL)
  

Calibrating SCIENCE observations made during the night with calibrations taken during the day relies on the stability and reproducibility of the positioning of the instrument components. To insure an accurate wavelength calibration, one of the critical criteria is the accuracy of the positioning of the gratings. If the highest possible accuracy is required for the wavelength calibration, an attached wavelength calibration should be taken with the science. Alternatively, since the exact grating position can not be measured in the science image itself, we rely on the daily health check format check data to verify the stability and reproducibility from day to day, assuming that this is a reaasonable indication of the reproducibility between nighttime science and daytime calibrations.

With this in mind the important aspects in these plots are the day to day scatter. The absolute level, within reason (i.e. plus or minus 10 pixels) is not important. From time to time there are sudden jumps in the mean levels, often due to earthquakes, but often the cause of the jump is far from obvious. Such jumps are not in themselves a cause for immediate concern. Only if they are happening frequently, and liable to be happening during the night. Or if they take the instrument so far from the Physical Model that the pipeline will have serious difficulties to converge to a solution, as a rule of thumb, intervention to realign should be considered if the residuals exceed plus or minus 10 pixels.