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Paul Bristow (INSY/SED/ESO) Thanks to:

Physical Model Driven Calibration. Paul Bristow (INSY/SED/ESO) Thanks to: Michael Rosa, Yves Jung, Florian Kerber, Andrea Modigliani, Sabine Moehler (ESO) Data Simulation Workshop – ESO Garching – April 2016. Brief history of IPMG.

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Paul Bristow (INSY/SED/ESO) Thanks to:

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  1. Physical Model Driven Calibration Paul Bristow (INSY/SED/ESO) Thanks to: Michael Rosa, Yves Jung, Florian Kerber, Andrea Modigliani, Sabine Moehler (ESO) Data Simulation Workshop – ESO Garching – April 2016

  2. Brief history of IPMG • 1999: Michael Rosa founded the Instrument Physical Modelling Groupinside the Space Telescope – European Co-ordinating Facility • Florian Kerber, Anastasia Alexov (later Mauro Fiorentino) & Paul Bristow • ST-ECF was wound up in 2006 • Legacy at ESO • Physical modelling and reference data for: • CRIRES • X-shooter

  3. Brief history of IPMG cont. • Projects included: • FOS • Wavelength scale (geomagnetic environment of HST) • Scattered light (grating analysis) • STIS • Wavelength calibration (discussed in detail below) • Simulated readout (CTE) • Reference data • HCL characterisation (spectral atlases, operational behaviour and ageing) • Material characterisation (e.g. refractive index data) • Recognised by a NASA group achievement award shared with NIST colleagues

  4. Astronet Roadmap 2009 “As a core fundamental element, and as a guide, it is recommended that funding provision for laboratory astrophysics be included in the planning of all astronomical and space mission research programmes at a level of the order of 2% of overall budget, with each programme taking “ownership” and peer-review of this part of the project.”Astronet Infrastructure Roadmap, p.132 Precision Radial Velocity, PSU 2010

  5. Calibration Reference Data • Traceable to laboratory standards >> “ground truth” • For wavelength calibration reference data link to frequency/time • Meta Data describing “what and how” • Error information • Documented by original data provider • Published Precision Radial Velocity, PSU 2010

  6. Physical Model Based Wavelength Calibration

  7. Matrix representation of optical components • 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).

  8. Physical Model Optimisation

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

  10. A Precautionary Note Regarding the CRIRES Implementation • Potentially more useful for CRIRES because of moving components • Never clear why it didn’t work properly • Erratic behaviour of the instrument did not help, but the problem was almost certainly with the model.

  11. 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 res’n, single slit • Single mode (no moving components) • Cassegrain & heavy => Flexure

  12. NIR Th-Ar HCL full slit

  13. Solar like stellar point source and sky

  14. Physical Model Optimisation FOR EVERY CALIBRATION EXPOSURE

  15. Effective camera focal length (mm) Effective camera focal length (mm) UVB Camera temperature sensor reading (°C) VIS Camera temperature sensor reading (°C)

  16. Detector tilt (°) Detector tip (°) Effective camerafocal length (mm) Modified Julian Date (days)

  17. 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 UVB VIS NIR

  18. Lab Measurements • NIR arm • Multi-pinhole • Translational & higher order distortions

  19. AFC Exposures • Obtained with every science obs => 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

  20. 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

  21. NIR

  22. NIR

  23. NIR

  24. NIR (Product moment correlation)

  25. VIS

  26. VIS

  27. Improvements and Updates • Full ray trace • computationally possible now • integration of eg. a Zemax library • Removes modelling assumptions (would be much easier to diagnose problems such as occurred for CRIRES) • No direct implementation in CPL • Despite fantastic support from Andrea and Yves… • It was still a huge overhead • Begin the development much earlier in the project lifetime • STIS: during operations • CRIRES: end of MAIT • X-Shooter: middle of MAIT • Ideal: During preliminary design phase

  28. Summary • Model based calibration is not a new concept • It has been applied with some success to HST and ESO instruments • Needs to be supported by appropriate reference data • In 2016 this is computationally inexpensive while the development represents a small investment relative to EELT instrument resources

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