near infrared spectro-polarimeter (nirsp) conceptual design
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
Near Infrared Spectro-polarimeter (NIRSP) Conceptual Design
Don Mickey
Jeff Kuhn
Haosheng Lin
August 25-28, 2003 NIRSP 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
August 25-28, 2003 NIRSP 3
NIRSP Requirements
Specification Requirement Goal PriorityWavelength Range 900–5000 nm 1
Spectral Resolution 50,000–300,000 1
Transmission 30% 1
Modulation efficiency 90% of max attainable 1
Polarimetric accuracy 10-4 Ic 5 10-5 1
Spatial Resolution 0.05 arc sec / pixel 0.025 arc sec / pixel 1
Spatial Field 3 arc min at 0.1 arc sec 5 arc min at 0.1 arc sec 1
Spatial Scanning Slit, step 0.05 arc sec Slit, step 0.025 arc sec 1
Wavelength Diversity 3 simultaneous 5 simultaneous 2
Obs with ViSP Flexible setup 1
August 25-28, 2003 NIRSP 4
Design Drivers
• Required spectral and spatial resolution• Field of view• Grating availability• Detector availability• Flux budget
August 25-28, 2003 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
August 25-28, 2003 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
August 25-28, 2003 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
August 25-28, 2003 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)
August 25-28, 2003 NIRSP 9
NIRSPC Layout
• R2 echelle• Littrow configuration, off-axis parabola• 3 m focal length
August 25-28, 2003 NIRSP 10
NIRSPC: Coudé Unit Specifications, f/40
Feed focal ratio f/40
Focal length 3040 mm
Slit width 39 m
Pixel size 39 m
Slit height 140 mm
Grating height 102 mm
Grating length 306 mm
Grating blaze angle 63.5°
August 25-28, 2003 NIRSP 11
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%
August 25-28, 2003 NIRSP 12
Coudé Characteristics, f/40
Spatial resolution 0.05 arc sec
Spatial field 3.0 arc min along slit
Spectral resolution 5.0 pm at 1565 nm
Size 3.5 x 1.2 x 0.6 m
August 25-28, 2003 NIRSP 13
NIRSPC: Coudé Unit Specifications, f/20
Feed focal ratio F/20
Focal length 2350 mm
Slit width 20 m
Pixel size 20 m
Slit height 70 mm
Grating height 204 mm
Grating length 410 mm
Grating blaze angle 63.5°
August 25-28, 2003 NIRSP 14
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%
August 25-28, 2003 NIRSP 15
Coudé Characteristics, f/20
Spatial resolution 0.055 arc sec
Spatial field 3.0 arc min along slit
Spectral resolution 3.3 pm at 1565 nm
Size 3.0 x 1.0 x 0.5 m
August 25-28, 2003 NIRSP 16
NIRSPC Background Estimates
Disk brightness
Coronal Brightness
Warm Bkg
Cold Bkg
F/20, R=475,000, pix=0.05” x 20 micron
August 25-28, 2003 NIRSP 17
Gregorian layout
August 25-28, 2003 NIRSP 18
NIRSPG: Gregorian Unit Specifications
Feed focal ratio F/13.1
Focal length 1300 mm
Slit width 250 m
Pixel size 250 m
Slit height 70 mm
Grating height 102 mm
Grating length 206 mm
Grating blaze angle 63.5°
August 25-28, 2003 NIRSP 19
NIRSPG Background Estimates
F/13, R=20,000 pix=1”x250micron
Disk
Corona Cold Bkg
Warm Bkg
August 25-28, 2003 NIRSP 20
Gregorian Characteristics
Spatial resolution 1.0 arc sec
Spatial field 4.7 arc min along slit
Spectral resolution 52.5 pm at 1075 nm
Size 1.5 x 0.5 x 0.4 m