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

2. August 25-28, 2003NIRSP2 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

3. August 25-28, 2003NIRSP3 NIRSP Requirements SpecificationRequirementGoalPriority Wavelength Range900–5000 nm1 Spectral Resolution50,000–300,0001 Transmission30%1 Modulation efficiency90% of max attainable1 Polarimetric accuracy10 -4 I c 5  10 -5 1 Spatial Resolution0.05 arc sec / pixel0.025 arc sec / pixel1 Spatial Field3 arc min at 0.1 arc sec5 arc min at 0.1 arc sec1 Spatial ScanningSlit, step 0.05 arc secSlit, step 0.025 arc sec1 Wavelength Diversity 3 simultaneous 5 simultaneous 2 Obs with ViSPFlexible setup1

4. August 25-28, 2003NIRSP4 Design Drivers Required spectral and spatial resolution Field of view Grating availability Detector availability Flux budget

5. August 25-28, 2003NIRSP5 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 10 6 –Give up some spatial and spectral resolution

6. August 25-28, 2003NIRSP6 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

7. August 25-28, 2003NIRSP7 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

8. August 25-28, 2003NIRSP8 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)

9. August 25-28, 2003NIRSP9 NIRSPC Layout R2 echelle Littrow configuration, off-axis parabola 3 m focal length

10. August 25-28, 2003NIRSP10 NIRSPC: Coudé Unit Specifications, f/40 Feed focal ratiof/40 Focal length3040 mm Slit width 39  m Pixel size 39  m Slit height140 mm Grating height102 mm Grating length306 mm Grating blaze angle63.5°

11. August 25-28, 2003NIRSP11 Grating Illumination, f/40 Grating illumination pattern –Feed f/40, slit 39  m, focal length 3.04 m –Grating 102 x 306 mm, tan  = 2 –Illumination height is from f/40; width is from slit diffraction –Light loss in wings is 14%

12. August 25-28, 2003NIRSP12 Coudé Characteristics, f/40 Spatial resolution0.05 arc sec Spatial field3.0 arc min along slit Spectral resolution5.0 pm at 1565 nm Size3.5 x 1.2 x 0.6 m

13. August 25-28, 2003NIRSP13 NIRSPC: Coudé Unit Specifications, f/20 Feed focal ratioF/20 Focal length2350 mm Slit width 20  m Pixel size 20  m Slit height70 mm Grating height204 mm Grating length410 mm Grating blaze angle63.5°

14. August 25-28, 2003NIRSP14 Grating Illumination, f/20 Grating illumination pattern –Feed f/20, slit 19  m, focal length 2.35 m –Grating 204 x 408 mm, tan  = 2 –Illumination height is from f/20; width is from slit diffraction –Light loss in wings is 18%

15. August 25-28, 2003NIRSP15 Coudé Characteristics, f/20 Spatial resolution0.055 arc sec Spatial field3.0 arc min along slit Spectral resolution3.3 pm at 1565 nm Size3.0 x 1.0 x 0.5 m

16. August 25-28, 2003NIRSP16 NIRSPC Background Estimates Disk brightness Coronal Brightness Warm Bkg Cold Bkg F/20, R=475,000, pix=0.05” x 20 micron

17. August 25-28, 2003NIRSP17 Gregorian layout

18. August 25-28, 2003NIRSP18 NIRSPG: Gregorian Unit Specifications Feed focal ratioF/13.1 Focal length1300 mm Slit width 250  m Pixel size 250  m Slit height70 mm Grating height102 mm Grating length206 mm Grating blaze angle63.5°

19. August 25-28, 2003NIRSP19 NIRSPG Background Estimates F/13, R=20,000 pix=1”x250micron Disk Corona Cold Bkg Warm Bkg

20. August 25-28, 2003NIRSP20 Gregorian Characteristics Spatial resolution1.0 arc sec Spatial field4.7 arc min along slit Spectral resolution52.5 pm at 1075 nm Size1.5 x 0.5 x 0.4 m