AAS 199th meeting, Washington, DC, January 2002
Session 102. Instrumentation for the Optical and Infrared
Display, Wednesday, January 9, 2002, 9:20am-6:30pm, Exhibit Hall

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[102.11] Resolution of Far-Infrared Astronomical Grating Spectrometers

E. F. Erickson, S.W.J. Colgan (NASA/Ames Research Center)

Contributions to grating spectrometer resolution from finite slit size and detector sampling are calculated. The intrinsic resolution accounting for round or elliptical collimated beams falling on the grating was obtained previously (E.F. Erickson & D. Rabanus, 2000 JApplOpt 39, 4486). In the far-infrared, non-optimum slit widths and detector sizes are often used to accommodate instrumental or technical limitations or observational preferences. We calculate the effect of finite slit size by convolution with the intrinsic resolution and provide an approximate, intuitive expression for the FWHM of the line spread function as a quadratic combination of the slit width and intrinsic width. The effect of finite detector size in sampling the line spread function is obtained by numerical simulation. We show that the notional Nyquist sampling limitation may be significantly surpassed when determinations of width and centroid location of an astronomical spectral line are made from measurements with realistic signal-to-noise levels.

The author(s) of this abstract have provided an email address for comments about the abstract: erickson@cygnus.arc.nasa.gov

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