1. The Prime Focus Imaging Spectrograph Design and Capabilities
Eric B. Burgh
SALT/PFIS Instrument Scientist

2. The Prime Focus Imaging Spectrograph
First generation, all-purpose spectrograph for SALT
Optical Imaging Spectroscopy and Spectropolarimetry 320 – 900 nm.
All-refractive collimator and camera using crystals for UV throughput
Upgrade capability for infrared camera
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29 October 2003

3. The Prime Focus Imaging Spectrograph Optics Layout
F/4.2 collimator, 150 mm diameter (fold mirror not shown)
Volume Phase Holographic gratings
Lead to need for articulating camera
F/2.2 camera, first element asphere
Articulates up to 100 degrees
(VPH grating a=50 deg in Littrow)
Polarimetric Optics
¼ and ½ waveplates, Wollaston beamsplitter
Double-etalon Fabry-Perot system
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29 October 2003

4. The Prime Focus Imaging Spectrograph Design Highlights
Weight/space constraints
Accessibility
Wavelength coverage:
Crystals (CaF2 and NaCl)
Anti-reflection coatings (0.5% reflections)
High UV Quantum Efficiency CCDs (Marconi)
Multiple configurations:
Complex mechanisms/interfaces
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29 October 2003

5. The Prime Focus Imaging Spectrograph
Grating Server
Collimator Optics
Camera
Detector Dewar
Slit Mask Server
Waveplate Mechanism
Filter Server
Articulation Rail
Open Truss Structure
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29 October 2003
Fabry-Perot Etalons

6. The Prime Focus Imaging Spectrograph
Grating Mechanism
Collimator Optics
Fold Mirror
Detector
Shutter
Slit Mask Server
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29 October 2003
Filter Mechanism

7. The Prime Focus Imaging Spectrograph
Camera Focus
Articulation
Slit Mask Server
Etalon Inserters
Wave Plate Mechanism
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29 October 2003

8. The Prime Focus Imaging Spectrograph Expected Performance
Expected system throughput of “fixed” optics.
Includes anti-reflection coatings and fold mirror reflectivity.
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9. The Prime Focus Imaging Spectrograph Expected Performance
Measured CCD efficiency for PFIS mosaic chips.
Chips will be arranged to take advantage of the high QE of Chip SALT-03 at “blue” end of mosaic.
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29 October 2003

10. The Prime Focus Imaging Spectrograph Grating Complement
Grating Complement (5 VPH gratings and one standard surface relief transmission grating)
Grating
Wavelength Coverage
Usable Angles (degrees)
Bandpass per tilt (nm)
Resolving Power (1.25 arcsec slit)
SR300
390—900 nm
390/440
250—600
G0900
320—900 nm
12—20
~300
600—2000
G1300
19—32
~200
1000—3200
G1800
450—900 nm
28—50
150—100
2000—5500
G2300
380—700 nm
30—50
100—80
2200—5500
G3000
320—540 nm
32—50
80—60
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29 October 2003

11. The Prime Focus Imaging Spectrograph VPH Grating Performance
VPH gratings have tunable blaze.
Best efficiency when used near Littrow (a=b)
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29 October 2003

12. The Prime Focus Imaging Spectrograph VPH Grating Performance
VPH grating complement superblaze curves.
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29 October 2003

13. The Prime Focus Imaging Spectrograph VPH Grating Performance
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29 October 2003

14. The Prime Focus Imaging Spectrograph Double-Etalon Fabry-Perot System
Double-etalon system isolates high-resolution, narrow bandpass.
High- and low-resolution modes:
R=500—12500
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15. The Prime Focus Imaging Spectrograph Current Status:
Optics: virtually all elements fabricated (some coated)
Mechanisms: Slit mask completed and wired, waveplate almost completed
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29 October 2003

16. The Prime Focus Imaging Spectrograph Upcoming Schedule Milestones
Structure fabrication (Rutgers) Jan 2004
Optomechanical assembly  Feb 2004
Integration and testing  thru Aug 2004
Commissioning  begin Sep 2004
Relevant web pages:
Observer’s guide v1.0 –
VPH Spectroscopy simulator –
PFIS photos –
Science with SALT – Cape Town
29 October 2003