Flexure analysis with the X-shooter Physical Model

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Flexure analysis with theX-shooter Physical Model

• Paul Bristow (ESO Instrumentation)
• Thanks to
• Andrea Modigliani, Joël Vernet Florian Kerber,
  Sabine Moehler (ESO)
• Paolo Goldoni, Frédéric Royer Régis Haigron
  (APC-SAp/CEA)
• Follow the Photons Edinburgh
  October 2011

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Matrix Representation of Optics

• ME is the matrix representation of the order m
  transformation performed by an Echelle grating
  with ?E at off-blaze angle ?. This operates on a
  4D vector with components (wavelength, x, y, z).

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Applications

• Wavelength calibration
• Simulations
• Early DRS development
• Effects of modifications/upgrades
• Instrument monitoring/QC
• Advanced ETC?

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Some background

• M. Rosa Predictive calibration strategies The
  FOS as a case study (1995)
• P. Ballester, M. Rosa Modeling echelle
  spectrographs (AAS 126, 563, 1997)
• P. Ballester, M. Rosa Instrument Modelling in
  Observational Astronomy (ADASS XIII, 2004)
• Bristow, Kerber, Rosa four papers in HST
  Calibration Workshop, 2006
• UVES, SINFONI, FOS, STIS, CRIRES,X-shooter
  Bristow et al (Experimental Astronomy 31, 131,
  2011)

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X-Shooter (300nm-2.5?m)

• Commissioned 2009
• Vernet et al. 2011.A A. in press
• Model for UVB, VIS NIR arms
• Same model kernel
• Independent configuration files
• Cross dispersed, medium resn, single slit
• Single mode (no moving components)
• Cassegrain heavy gt Flexure

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NIR Th-Ar HCL full slit
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Solar like stellar point source and sky
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X-shooter Flexure

• Backbone flexure
• Causes movement of target on spectrograph slits
• Corrected with Automatic Flexure Compensation
  exposures
• Spectrograph flexure
• Flexing of spectrograph optical bench
• Can also be measured in AFC exposures
• First order translation automatically removed by
  pipeline

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Lab Measurements

• NIR arm
• Multi-pinhole
• Translational higher order distortions

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AFC Exposures

• Obtained with every science obs gt large dataset
  300 exp from Jan May 2011
• Single pinhole, Pen-ray lamp
• Window
• 1000x1000 win (UVB 12/VIS 14 lines)
• Entire array (NIR 160 lines)

VIS
UVB
NIR
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Physical Model Optimisation
FOR EVERY CALIBRATION EXPOSURE
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Choosing open parameters

• All parameters open
• Slow
• Optimal result
• Degeneracy
• Physically motivated
• Related to flexure
• Constrained by data
• In these results
• Prism orientation Grating Orientation Grating
  constant Camera focal length Detector position
  and orientation

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NIR
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NIR
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NIR
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NIR
(Product moment correlation)
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VIS
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VIS
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VIS
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UVB
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UVB
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UVB
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Summary

• Simple physical modelling approach
• wavelength calibration for a number of
  instruments
• Raw data simulation
• Instrument monitoring
• Application to X-shooter
• Flexure monitoring
• Allows identification of physical model
  parameters that correlate with instrument
  orientation

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Physical Model Optimisation
QC Data 9 pinhole mask, arc lamp Th-Ar (UVB 250
lines x 9 VIS 390 lines x 9) pen-ray (NIR 140
lines x 9) Daytime, Zenith (no flexure except
hysteresis) 1/week gt small data
set Automatically processed by pipeline (ESO QC)
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Effective camera focal length (mm)
Effective camera focal length (mm)
UVB Camera temperature sensor reading (C)
VIS Camera temperature sensor reading (C)
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Detector tilt ()
Detector tip ()
Effective camerafocal length (mm)
Modified Julian Date (days)
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• Explain our Physical Models
• Compare to poly
• Uses
• Calibration
• Simulation
• Test DRS
• Investigate modifications/upgrades
• Monitor/understand instrument behaviour
• History (Ballester Rosa)
• Introduce X-shooter
• Overview
• Flexure
• Lab plots
• AFC
• Calibration exposures
• Flexure Procedure
• Optimisation for 1 exposure
• Apply to all data
• Choosing open parameters