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Near Infrared Spectro-polarimeter (NIRSP) Conceptual Design

Near Infrared Spectro-polarimeter (NIRSP) Conceptual Design. Don Mickey Jeff Kuhn Haosheng Lin. NIRSP Mission . Measure polarization state of spectral lines Near infrared, 900–5000 nm wavelength Very wide range of observational parameters Science Sunspot, active region magnetic fields

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Near Infrared Spectro-polarimeter (NIRSP) Conceptual Design

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  1. Near Infrared Spectro-polarimeter (NIRSP) Conceptual Design Don Mickey Jeff Kuhn Haosheng Lin

  2. NIRSP Mission • Measure polarization state of spectral lines • Near infrared, 900–5000 nm wavelength • Very wide range of observational parameters • Science • Sunspot, active region magnetic fields • Network, internetwork magnetic fields • Coronal magnetic fields • Filament, prominence magnetic fields • Waves and dynamics, coronal heating NIRSP

  3. NIRSP Requirements NIRSP

  4. Design Drivers • Required spectral and spatial resolution • Field of view • Grating availability • Detector availability • Flux budget NIRSP

  5. Disk vs. Coronal Observations • Disk observations: • High spatial and spectral resolution • High polarimetric precision • Good temporal resolution • “Plenty” of flux • Corona: • High polarimetric precision • Flux is lower by 106 • Give up some spatial and spectral resolution NIRSP

  6. NIRSP Has Two Subunits • NIRSPC: Coudé Unit • Disk observations • High resolution • Littrow, parabola • Multiple cameras possible • NIRSPG: Gregorian Unit • Coronal observations • Limited spatial and spectral resolution • High throughput • Littrow, parabola • Cryogenic NIRSP

  7. Distributed NIRSP Concept • Common Elements • similar optical design • Hawaii-1RG arrays or -2RG HgCdTe camera • Interchangeable mechanism designs (all warm steppers) • Common hardware and software control/interface structure • Distinct Elements • NIRSPG uses cooled grating/optics (warm steppers) • NIRSPC warm optical bench NIRSP

  8. Baseline NIRSP Status • Spectrograph design proof-of-concept • Fiber bundle IFU desirable • Multislit mode desirable • Optomechanical and cryogenic designs TBD • Polarimeter concept designs beginning • NIRSPG favors SAP concept w/ polarizing beamsplitter • NIRSPC... • Exploring trades • Multiple or single HgCdTe camera modules • 2.5 vs 5 micron cutoff) NIRSP

  9. NIRSPC Layout • R2 echelle • Littrow configuration, off-axis parabola • 3 m focal length NIRSP

  10. NIRSPC: Coudé Unit Specifications, f/40 NIRSP

  11. Grating Illumination, f/40 • Grating illumination pattern • Feed f/40, slit 39 mm, focal length 3.04 m • Grating 102 x 306 mm, tan q = 2 • Illumination height is from f/40; width is from slit diffraction • Light loss in wings is 14% NIRSP

  12. Coudé Characteristics, f/40 NIRSP

  13. NIRSPC: Coudé Unit Specifications, f/20 NIRSP

  14. Grating Illumination, f/20 • Grating illumination pattern • Feed f/20, slit 19 mm, focal length 2.35 m • Grating 204 x 408 mm, tan q = 2 • Illumination height is from f/20; width is from slit diffraction • Light loss in wings is 18% NIRSP

  15. Coudé Characteristics, f/20 NIRSP

  16. NIRSPC Background Estimates F/20, R=475,000, pix=0.05” x 20 micron Warm Bkg Disk brightness Cold Bkg Coronal Brightness NIRSP

  17. Gregorian layout NIRSP

  18. NIRSPG: Gregorian Unit Specifications NIRSP

  19. NIRSPG Background Estimates F/13, R=20,000 pix=1”x250micron Disk Warm Bkg Cold Bkg Corona NIRSP

  20. Gregorian Characteristics NIRSP

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