LWS
Quick Reference
This page summarizes the spectroscopic capabilities of the LWS. 

Estimated Spectroscopic Performance

Total slit length 10.24 arcsec
Usable slit length¹ 8.7 arcsec or 85% (
Detector scale along slit 0.080 arcsec per px (75 µm px) 
Wavelength range (spectra) 3.5-25 µm
Order blocking filters N wide (7.73-13.31 µm)
Spec 10 (>7.52. µm long pass) 
Spec 20 (>13.93 µm long pass) 
Slit widths 3 pix,  6 pix, and 12 pix wide 
(0.24, 0.48, and 0.96 arcsec)
Current gratings 8 g/mm (10.0 µm blaze); R=100
50 g/mm (19.5 µm blaze); R=1400 
Number of avalable gratings Two
Corresponding dispersions LRES:     0.037 µm/px;
HRES:    0.0024 µm/px (10 µm, N=2) 
HRES:    0.0048 µm/px (20 µm, N=1)
Spectral coverage, single exposure (128 px) LRES: 4.7 µm
HRES (@10.0µm): 0.31 µm
HRES (@20.0µm): 0.62 µm
FWHM resolution R=100 and R=1400 (3 px slit)
Count rate at 10µm TBD
Sensitivity to faint stellar objects² 150 mJy

Transmission curves for the order blocking filters available in the LWS may be found on the filter page.

A Time Estimator is available on the LWS web site that predicts the amount of on-source integration time needed to acquire a user specified signal-to-noise for spectroscopic observations..

Notes:

  1. Slit length subtended by detector pixels.
  2. Signal level yielding S/N=1 per spectroscopic resolution element in 1 sec on source at 11.7 µm using the small (3 pixel = 0.25 arcsec) slit in conjunction with the low-resolution grating and the broadband "N" (8-13 µm) filter at a wavelength of 10 µm. Chop-nod observing mode is assumed. Quoted flux is light incident on telescope. Note that the observing efficiency is approximately 30% in spectroscopic mode; i.e., 30% of the time is spent in the "off beam" and 40% is lost to overhead associated with telescope moves.
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Last modified: 8 Apr  2002