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TECHNICAL FEASIBILITY OF SWIFT

The guiding design principle of SWIFT is that it is an integrated telescope+spectrograph optimized for wide-field, extremely efficient, and highly multiplexed slitlet spectroscopy. To achieve this goal, the spectrograph and telescope optics are designed together as a system. The primary design objective is to preserve as wide a field of view as possible on as large an aperture as possible without compromising the capability for highly efficient beam-fed spectroscopy. In this section, we outline one possible realization of SWIFT which minimizes risk and can be built at the present time. Although the current design demonstrates the technological feasibility of the concept as an `existence theorem', in practice there are various technological paths we intend to investigate in order to maximize the scientific effectiveness of this facility and enable us to determine the relevant technological paths to future instrumentation on the next generation of large-aperture telescopes.


  
Figure 13: SWIFT occupies a unique region of parameter space when compared with existing and planned multi-object spectrographs. Fiber systems are shown in blue, beam-fed systems in red. The size of the labels is proportional to the limiting magnitude. SWIFT can target 2000-10000 sources at a time.


 
Table 5: Baseline Concept for SWIFT
Fore-optic >8-m diameter effective aperture
Field of view 1.5o diameter
Wavelength range 0.36 -- 1.7 micron
Spectral resolution 500, 5000, 25000
Image quality <0.25 arcsec1
Slitlet density 2000--10000
Total system throughput 50% optical; 40% near-IR
Detectors CCD Mosaics
  InSb Mosaics

1 80% encircled energy diameters for `white' light (0.36--1.7m ) over the entire field.  



 
Table 6: Existing & Planned Spectrographs on Large Aperture Telescopes
Telescope Aperture Spectrograph FOV Comments
WIYN 3.5 Hydra 0.05 60' dia. 100 fiber
Mayall 3.8 SamSpec 0.45   slit
Blanco 3.9 Hydra-CT 0.05 40' dia 138 fiber
AAT 3.9 2DF 0.05   400 fiber
Magellan 6.5 IMACS 0.3? 600 slit
MMT 6.5 Hectospec 0.243 60' dia 300 fiber
MMT 6.5 Binospec 0.40 <150 slit
3DT 8.4m 6.9   0.1? 180' dia. <500 fiber
Gemini 8.1 GMOS 0.40 <600 slit
VLT 8.2 VIRMOS 0.3? 150-750 slit
Subaru 8.3 FOCAS       slit?
HET 9.2 LRS 0.40 4' dia. 13 slit
Keck 10 LRIS 0.35 20 slit
Keck 10 DEIMOS 0.35 80 slit
GTC 10 ODIN 0.05? 12' dia 60 fiber
GTC 10 OSIRIS ? 8' dia 15 slit
GTC 10 EMIR ? 6' dia 10 fiber or slit?
SWIFT 8.4   0.45 90' dia. 2000-10000 slit
 

1 Optical throughput of spectrograph and telescope.

2 Maximum number of objects which can be simultaneously observed.

3 Sky subtraction with fibers sets a limit of  mag on faint-object spectroscopy.




 
next up previous contents
Next: The Front-End Optics: Telescope Up: SWIFT: Spectroscopic WIde Field Previous: SYNERGY WITH SPACE-BASED MISSIONS
Arjun Dey
1999-05-29