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Prospects – JWST, EUCLID, WFIRST Jeff Kruk (GSFC)

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Presentation on theme: "Prospects – JWST, EUCLID, WFIRST Jeff Kruk (GSFC)"— Presentation transcript:

1 Prospects – JWST, EUCLID, WFIRST Jeff Kruk (GSFC)

2 Outline HST: now to 2015 and beyond… JWST: EUCLID(?): WFIRST: XX - XX+5… 11/15/20102J. Kruk STScI Slitless Spectroscopy wkshp

3 Sky backgrounds 11/15/2010J. Kruk STScI Slitless Spectroscopy wkshp3

4 HST slitless modes InstrumentFoV (arcmin) PlatescaleRBandpass (nm) ACS WFC grism 3.4’x3.4’0.05” ACS SBC prisms 0.58’x0.51’0.025” WFC3 NIR grisms 2.05’x2.27’0.13” WFC3 UVIS grism 2.7’x2.7’0.04” NIC3 prisms0.87’x0.87’0.203” STIS NUV prism 0.42’x0.42’0.024” /15/20104J. Kruk STScI Slitless Spectroscopy wkshp

5 JWST slitless modes InstrumentFoV (arcmin) PlatescaleRBandpass (nm) NIRCAM 2 grisms, Rotated 90° 2.16’x2.16’0.0648” (filters in series) NIRSpec* prism, gratings 3.4’x3.6’0.1” , *NIRSpec micro-shutters: 0.2”x0.45” - open area ratio is 0.7 if all left open 11/15/20105J. Kruk STScI Slitless Spectroscopy wkshp

6 EUCLID NIR slitless spectroscopy Launch in 2018 if selected, 5 year mission duration Survey deg 2 – limiting line flux 4* ergs/cm 2 /s Characteristics (Laureijs et al 2010 SPIE 7731): – 1.2m primary, 0.35m secondary obscuration – 4 grisms in wheel, identical except for 90° rotations – microns – R=500 – Focal plane: (choice still TBD?) 12 SCAs: 0.33”/pix 36.4’x48.5’ (0.49 sq deg) 16 SCAs: 0.31”/pix 46.1’x46.1’ (0.59 sq deg) 11/15/20106J. Kruk STScI Slitless Spectroscopy wkshp

7 WFIRST Launch: ?? - depends on JWST schedule Mission duration: 5 years min, 10 years goal Objectives: – deg 2 WL survey (30 gal/sq arcmin) – deg 2 BAO survey (limiting flux ) – 150 SNIa per  z=0.1 – (didn’t quite fit into 5 years, but close) EOS panel recommendations cuts time in ~half for first 5 years of mission 11/15/20107J. Kruk STScI Slitless Spectroscopy wkshp

8 WFIRST characteristics (details subject to change!) Imager –  m – 0.18”/pixel – 4x6 array of SCAs (0.25 deg 2 ) – Filter wheel: 5 filters, R=75 prism, blank Spectrometers (2, w/ opposing dispersions) –  m – 0.37”/pixel – 2x3 array of SCAs (0.26 deg 2 ) each – R= per 2 pixels R  = ”, or c/R  = km/s/arcsec 11/15/20108J. Kruk STScI Slitless Spectroscopy wkshp

9 WFIRST block diagram (details almost certain to change) 11/15/20109J. Kruk STScI Slitless Spectroscopy wkshp

10 WFIRST focal planes as projected onto the sky 11/15/201010J. Kruk STScI Slitless Spectroscopy wkshp

11 Design Trades grism vs. prism Grism pros: – zero-order gives wavelength reference – Allows higher dispersion Grism cons: – Zero order increases spectral contamination – Higher dispersion not needed for BAO; if lines resolved, S/N is reduced – Higher orders contaminate spectra – 1 st order throughput lower than prism 11/15/201011J. Kruk STScI Slitless Spectroscopy wkshp Grism simulation courtesy of David Larson

12 Design Trades Dispersion – σ z /(1+z) < 0.001, resolve O III, don’t resolve Hα Bandpass – Redshift coverage & spectral diagnostics vs zodiacal light – Combined w/dispersion -> length of spectral trace Number of roll angles, size of roll offset – 4 rolls: 0°,5°; 170°,175° found sufficient Don’t set 2 spectrometers exactly 180° apart 11/15/2010J. Kruk STScI Slitless Spectroscopy wkshp12

13 Imager sim – 225 sec 11/15/2010J. Kruk STScI Slitless Spectroscopy wkshp13 Imager simulation – 225sec 1SCA (log stretch) Courtesy David Larson

14 11/15/2010J. Kruk STScI Slitless Spectroscopy wkshp14 Spectrometer simulation – 225 sec 1SCA (log stretch) Courtesy David Larson

15 4° roll offset 11/15/2010J. Kruk STScI Slitless Spectroscopy wkshp15 Roll = 0Roll = 4

16 11/15/2010J. Kruk STScI Slitless Spectroscopy wkshp ksec deep exp (SN field) asinh stretch Galaxies & stars only - no background Courtesy David Larson

17 General issues EUCLID, WFIRST not as clean as HST – PSF, pixels are large compared to HST – Pointing stability, dithering, less precise than HST What dithering is desirable/required in this context? Direct images are obtained with a different instrument at different times – Use edges of traces of bright stars in field for registration 11/15/2010J. Kruk STScI Slitless Spectroscopy wkshp17

18 Issues continued: calibrations BAO needs accurate wavelengths Optical distortion calibration is critical – not challenging SNIa needs accurate fluxes If from spectra, flat-field cube is critical – challenging Would like to derive flat-field internally from the data – Has been done for imaging instruments (Arendt et al ApJS ) – Dimensionality of problem is higher for slitless spectrometer; will need extensive simulations to test Persistence corrections Can pipeline maintain continuous exposure history? Initial planning limited to DE programs – Need to reevaluate for larger WFIRST program 11/15/2010J. Kruk STScI Slitless Spectroscopy wkshp18

19 Issues cont. Datasets are large! – Manual processing not practical for 10 9 galaxies Extract ~10 9 to obtain 10 8 emission-line galaxies – “…it is still mandatory to check and validate the products before any science investigation can commence. ” (The WFC3 IR Grism Data Reduction Cookbook – Extracting several 100 grism spectra made easy) 11/15/2010J. Kruk STScI Slitless Spectroscopy wkshp19

20 Issues cont. Datasets are large! – Manual processing not practical for 10 9 galaxies Extract ~10 9 to obtain 10 8 emission-line galaxies – “…it is still mandatory to check and validate the products before any science investigation can commence. ” (The WFC3 IR Grism Data Reduction Cookbook – Extracting several 100 grism spectra made easy) Uh Oh….. Crowd-sourcing? Doesn’t look like as much fun as the Galaxy zoo 11/15/2010J. Kruk STScI Slitless Spectroscopy wkshp20

21 WFIRST - what’s next? Astro-2010 provided fairly strict guidance, – But details left open for further optimization The science goals have expanded to fill a 10- year mission. – While plausible, the nominal design life is 5 years (so everyone starts out unhappy) The Science Definition Team may have a big role in defining the details. Stay tuned. 11/15/201021J. Kruk STScI Slitless Spectroscopy wkshp

22 WFIRST telescope trade: 1.5m on-axis vs 1.3m off-axis 11/15/201022J. Kruk STScI Slitless Spectroscopy wkshp PSF - scaled by effective area Encircled Energy Diffraction from spider arms not included

23 EOS observing plan BAO+WL: <~2 years Sne: 0.5 years Micro-lensing (Galactic bulge): 1.4 years Galactic plane survey: 0.5 year Guest-observer surveys: 1 year – This means you! 11/15/2010J. Kruk STScI Slitless Spectroscopy wkshp23

24 WFIRST SDT Deadline for applications to the WFIRST Science Definition Team: Nov 23 rd, 2010 Please Apply! Further info: 11/15/2010J. Kruk STScI Slitless Spectroscopy wkshp24


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