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| UVES
Quality Control:
Format check |
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This tutorial provides information for the Echelle grating position. It is based on the measurement of QC1 parameters of FORMAT CHECK calibration data. These are obtained with dedicated Health Check OBs executed daily. These OBs obtain four sets of FORMAT CHECK data, 2 sets in BLUE mode and 2 sets in RED mode, each set comprising a single RAW frame. Each set is acquired in a different wavelength setting covering the two arms and the four cross dispersers.
QC1 parameters 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.
QC1 parameters The recipe also performs a comparison between the detected line positions and a reference frame. This information is in principal redundant but monitored to safeguard against instabilities in the physical model prediction.
These parameters are stored in the QC1 database but not monitored on the HC monitor to avoid redundancy of alerts.
Modes
Formatcheck frames are measured daily whenever UVES is
operational. They are used to monitor the orientation of the four crossdispersers and
the two gratings. For each crossdisperser, one standard setting is used:
QC1 parametersFive QC1 parameters are measured:
The results of the comparison to the physical model are plotted. The shifts are evaluated as function of time and as function of temperature T which is the main parameter for daily drifts. Typically 300-1100 lines are selected per CCD for this analysis. These QC1 parameters are plotted for all four settings. The red settings have data for the two CCDs (REDU and REDL). Y drifts versus temperatureA compensation for thermal drifts in X and Y is active since November 2000 for all four gratings. Their coefficients are monitored in the HC plots "Thermal_<ccd>". Notes (until 2003) 1. A 5.9 mag earthquake on 2000-05-12 shifted the blue gratings by more than -10 pixels (see DY panels 346B, 437B from Apr-Jun2000). The blue gratings have been readjusted on 2000-07-24. 2. In addition to thermal Y drifts, there are from time to time sudden shifts (e.g. earthquake, readjustments). Also slow non-thermal Y drifts (timescale of months) have been observed. 3. Since 2001-12-26, a thermal compensation in X (dispersion) direction has been activated. 4. The trending of N_sel gives an indication about the quality of the DY correlation. If the Y position of a grating starts drifting away from its nominal zeropoint (or is suddenly pushed away), then usually N_sel is the most sensitive parameter for detecting whether or not this is critical and requires immediate reaction. A good example is the period JUL-SEP 2001 where the N_sel parameter for grating 4, REDU CCD, faded away from its reference value (about 320) to less than 200. This indicated a critical regime at least for the UVES pipeline to find the proper dispersion solution. 5. From 2002-05-29 to 2002-06-17, the positons of the red crossdispersers could not be set with high accuracy. This was caused by high friction and contamination of the red crossdisperser bearing. The crossdispersers have been repaired on 2002-06-17. All observations which have been affected by this problem have been re-scheduled. EventsA list of events which affect the grating positions is available (until 2003). See also the history of the HC plots for a more complete data history.
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