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DL – IFU (Prieto/Taylor). Slicer: 25mas sampling … 0.9mm slices ~f/250 (assuming no anamorphism) Detector = 2k array of 18um pixels Slit subtends 1-pixel (spectral dithering as for TiPi) Camera f-ratio = f/5 (double TMA a la JWST system) Full window requires ~800 pixels
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DL – IFU(Prieto/Taylor) • Slicer: • 25mas sampling … 0.9mm slices • ~f/250 (assuming no anamorphism) • Detector = 2k array of 18um pixels • Slit subtends 1-pixel (spectral dithering as for TiPi) • Camera f-ratio = f/5 (double TMA a la JWST system) • Full window requires ~800 pixels • 4 slits per spectrograph/detector • Slit height = ~1000 pixels or 30-by-30 slicer with FoV ~0.752 arcsec. • 4 slits gives FoV ~1.52 arcsec. • Is this a sufficient field ? Or do we need 2 or 4 units ? • NB: SRD asks for ~42 arcsec • If only we could use a 42k, 9m pixel, array at f/2.5 ! • Assume fore-optics can switch in factor of 5 magnification to give: • 25mas ; 20mas; 15mas; 10mas; 5mas • 5mas option would feed spectrograph at f/12.5 • What beam-size would be required ? 50mm OK ?
Optical Components • Cool box: • 45 deg. fold to vertical • Pupil imager onto ~25mm DM • Field lens or Field mirror ? (not exactly at focus) • DM as steering mirror • feeding mirror at field stop (as in TiPi) • but also an imaging system (as in TiPi) to give ~10 arcsec D-L field • DM can switch from IFU to direct imaging field by small tip/tilt • Object can be viewed directly and then selected into IFU field • Surrounding objects can be imaged directly while doing IFU spectroscopy
Optical Components • Cryo box: • Magnification optics and scale changer optics • Non-anamorphic (25mas ; 12.5mas ; 5mas) • Cold stop (rotating ?) • 2 contiguous 60-slice slicer units • square FoV • 2 slits into 1 spectrograph • Double TMA spectrograph (a la JWST/NIRSPEC) • Collimator somewhere between f/10 and f/20 (tbd) • Camera f/5 • Beam size ~50mm (plus pupil diffraction)
Scope of Work • Optical concept at same level as TiPi • Field lens/mirror • DM – steering & image/IFU selector • Imaging system (FoV ~10” D-L) • Fore-optics / scale changer • Slicer unit • Spectrograph • Approx. wave-front error budget ? • Challenges: • Larger FoV ~3 arcsec2 ? • Faster cameras ~f/2.5 ?