1. A. Ealet Berkeley, december 2002 1 Spectrometer simulation Note in http://www.astrsp-mrs/snap/spectro/spectrosim.ps ● Why we need it now ● What should be simulated ● How to do it ● Work plan ● Conclusion A.Bonissent A.Ealet C.Macaire E.Prieto A.Tilquin

2. A. Ealet Berkeley, december 2002 2 ● Previous stage, only laboratory tests and simulation of slicer alone have been performed. ● This is sufficient to ensure that an instrument can be built with adequate performance. ● Now to study the real performances on the full instrument, we need a complete simulation Past

3. A. Ealet Berkeley, december 2002 3 ● Needed in the present phase for – Optimizing the design: balance cost and simplicity (reliability) for best possible physics – compute realistic efficiency – evaluate tolerance – evaluate calibration procedure – produce realistic data to develop and test data processing algorithms ● At term, it will be used in detailed MC studies for physic analysis Why

4. A. Ealet Berkeley, december 2002 4 Specifications OK ? Optical design Optical simulation No Optomechanical simulation Library of psf yes Optimisation process

5. A. Ealet Berkeley, december 2002 5 ● At the end of phase A, we need a Final design of the instrument with estimated (and justified) performances ● Simulation and data reduction software for evaluation should be ready well before simulation spring 2003 data reduction prototype spring 2004 Développement plan

6. A. Ealet Berkeley, december 2002 6 ● Full SNAP simulation SN simulation analysis propagation Data reduction instrument Detector pixel data physic Data cube Lightcurve spectra Lightcurve spectra Cosmo models Physic parameters

7. A. Ealet Berkeley, december 2002 7 ● Spectrometer simulation telescope optical sim readout pixellisation slicer spectrograph fit Data cube i,j,adc Parameterization constants x,y, x,y  psf1 x,y, psf2 x,y, psf3 i,j,Qij Pixel parameterization

8. A. Ealet Berkeley, december 2002 8 TF of amplitude from object plane to pupil plane then to image Apply geometry and phase (zernike) on pupil Apply geometry on image Compute intensity to evaluate efficiency Interpolate position x,y at each step (need parametrisation) Output is position on the detector for each point and wavelength with an associated PSF Very long and CPU intensive Method Telescope xt,yt, Slicer xs,ys Slit xf,yf prism xl,yl Detector xd,yd pe i  Compute Psf and transmission at each x,y, pupil xp,yp TF ppe i  p psf TF

9. A. Ealet Berkeley, december 2002 9 Psf shape and size depends on x,y, (small amount of) energy is lost by diffraction Geometry affects performance psf slice

10. A. Ealet Berkeley, december 2002 10 0.9  m 1.7  m Slice 0 Slice 2

11. A. Ealet Berkeley, december 2002 11 Zernike Polynomia from Zeemax are used to introduce aberrations Depend of ,x,y They need to be extrapolate on each point of the image plan Use Neural Network technique to do extrapolation Zernike polynomial of slicer for  = 1.7  m

12. A. Ealet Berkeley, december 2002 12 psf slice Efficiency study Gobal efficiency Telescope+slicer+spectrograph

13. A. Ealet Berkeley, december 2002 13 R=  /  pixel Simulation checking: spectral resolution

14. A. Ealet Berkeley, december 2002 14 ➢ DESIGN OPTIMISATION ➢ Test optic ➢ Play with optic to study tolerance ➢ Efficiency/nb of pixel ➢ Visible/IR efficiency vs spectral resolution/detector ➢ optimise spatial resolution => detector noise optimisation ➢ Reduce Nb of mirrors : better transmission but may need more space, more complex optics ● TEST DATA – Slit effect : Position of SN in slice => translation of spectrum; – SN may cover several slices : need to add translated spectra – Optical distorsions – Pixellization – Dithering – Detector and electronics : efficiency, noise, cosmics... Used for :

15. A. Ealet Berkeley, december 2002 15 Distorsions on the detector U spatial dimension V spectral dimension Detector pixels do not coincide with = Cte or x = Cte 20 pixel/slice

16. A. Ealet Berkeley, december 2002 16 Full simulation of slicer unit OK Full simulation of telescope and spectrometer OK Interpolate for intermediate points using Neural Network technique. OK library of PSF for a grid of x,y, ; under work From library of PSF+ geometry (x,y,  -> detector indices) to be done Pixellisation : integrate over pixels Add dark current, readout noise etc... Include galaxy Dithering (spatial, spectral) If useful, we may use general purpose code developed by CRAL (SNIFS, SN factory). Current Status

17. A. Ealet Berkeley, december 2002 17 ● Detailed simulation of the spectrometer is needed in this phase to quantify performances ● CPU intensive : not appropriate for physics simulation ● Parametric simulation under development, based on the library of PSF should be appropriate for a full SNAP simulation (not for SNAPfast). Conclusion

18. A. Ealet Berkeley, december 2002 18 Spectrograph: Performances telesc ope Relay optics Slicer Optic straylight diffra. Spectro Mirrors prism dichroic Detector Vis / NIR #elem ents 4131121 1 1 1 Effici ency/ 0.98 0.990.950.980.810.950.9 0.6 (0.8) cumul ative 0.920.900.850.840.800.770.620.590.53 0.35 (0.47) Gain on mirror transmission, loose on diffraction/prism (complete simulation) Globally equivalent

19. A. Ealet Berkeley, december 2002 19 Design issues Spectral resolution : optimization visible /IR ( R(IR [1-1.4]  m) < 100 but don’t need to join the 2 detectors ) Polarization: specification needed – impact on spectrograph Design Spatial resolution : 0.15”. Issue vs the radiation rate Wavelength range 1.7  m short for the Si line, 1.8 mm better but detector  cut issue, issue on temperature