Presentation on theme: "Anthony Boccaletti Observatoire de Paris LESIA. Several instruments dedicated to Exoplanet detection and characterization with High Contrast Imaging since."— Presentation transcript:
Several instruments dedicated to Exoplanet detection and characterization with High Contrast Imaging since 2001 For this decade : SPHERE and GPI : 2011/12 JWST-MIRI: 2015 For the future (>2020-25): ELT / EPICS Space coronagraphs : ACCESS, PECO, SPICES …. => need for simulation tools adapted to the instruments and to the observing cases
Effectsissuessolutions Stellar diffraction- photon flux - photon noise coronagraphy Wavefront errors (dynamic and static) - speckle noise - photon noise wavefront sensing and correction Residual aberrations (mostly static) - un-seen - un-corrected speckle calibration differential imaging Issues or noises related to Image formation (so to the source itself)
Background : sky, thermal emission of instrument/telescope, zodiacal light, exozodi Detector related : Flat Field, readout noise, remanance, … Many others that we don't even thought about !!! simulator coronagraphy Wavefront aberrations Differential imaging Background Detectors artifacts Targets characteristics
Assess the performance for a science case Evaluate the limitations : which source of noise, or which issues are relevant ? Put some constraints on the instrument design Optimize the design itself (instrumental choices) And then => reassess the performance
plan focal + diaphragme pupille détecteur pupille FFT FFT -1 FFT + masque Plan A Plan B Plan C Plan D
Sampling of the pupil : good sampling needed to reproduce pupil shape Make use of grey approx. Sampling of the image PSF size = N / D = lambda/D (N: array size, D: pupil diameter) PSF chromaticity Modify pupil size but keep the array constant => change the actual shape of the pupil Modify array size but keep the pupil constant Uses of FFT with IDL Shift the center to coordinates [0,0] Aliasing: make sure N is at least 2xD
Image normalization: use an off-axis object far from the center (not affected by the mask) but account for the throughput Wavefront errors: Define the Power Spectrum Density of aberrations with power law and cut-off frequencies WFE screen = random screen X sqrt (PSD)
2 codes : 1 for image formation and 1 for contrast curves Image formation – Make pupil – generate common aberrations + differential temporal aberrations upstream – Build complex amplitude in pupil – Build PSF complex amplitude – Make coronagraphic image for on-axis and off-axis objects – Save results Contrast curves – Read results – Normalize – Resample 1 to 0 – Calculate various subtraction – Plot contrast curves
Image formation – Start with circular pupil then use the routine sph_pupil to produce VLT pupil in grey level. – Generate diaphragm (under/over-sized) – Define bands: H2 H3 filters of SPHERE = 1.593 & 1.667 microns – upstream aberrations : use the provided VLT_wfe.fits Add a 4nm defocus on the reference target – Define a loop on filter and scale array size accordingly – Calculate complex amplitude in pupil : sph_amp_complex.pro – Build PSFs with sph_psf.pro – Introduce differential aberrations with sph_wfdiff.pro – Build coronagraphic images with sph_corono.pro – Take intensities – Rescale the arrays to 1kx1k with sph_taille.pro – Produce off-axis planets with sph_planet.pro – Save results
Contrast curves: – Read results of image formation – Resample to camera pixels (shannon at 0.95mic) make use of sph_rescale.pro – Resample of image at 1 to 0 (again sph_rescale.pro ) – Calculate subtractions: obj( 0)-ref( 0) obj( 0)-obj( 1) [obj( 0)-obj( 1)] – [ref( 0)-ref( 1)] – Azimuthal contours with sph_profil1d.pro – Plot averaged contour for psf and corono image and 5sig level for subtractions
And play with the parameters …. D = 8m / 160 pix N = 1024 40 linear actuators Relative offset (star/ref) = 0.5 mas Differential aberrations = 10nm Planet separations = 0.1", 0.5", 1"
Reference to : – CAOS + SPHERE Software package (public) – PROPER by John Krist (public) – PESCA for ELT (not public)
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