LWS Home Page
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LWS Home Page |
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About the Keck Long Wavelength Spectrometer (LWS) |
The LWS dewar is an ``uplooker,'' meaning that the instrument looks directly at the telescope secondary with no tertiary mirror. All optical components behind the dewar window are cooled to liquid helium temperature, except for the detector which is maintained at 8.52±0.02 K via a precision closed-loop thermal control system. All 10 reflecting surfaces inside LWS are gold coated for high reflectivity (1% loss per surface).
A rotating grating turret contains the low- and high-resolution gratings, plus a mirror for direct imaging. The plate scale of 0.08 arcsec/px adequately samples the 0.25 arcsec (FWHM) diffraction limited point spread function at 10 µm while providing a 10.2×10.2 arcsec imaging field of view. Two gratings enable spectroscopy at resolutions of R=100 (blazed at 10.0 µm) or 1400 (blazed at 19.5 µm) over the 3-25 µm range. Chopping and chop/nod observing modes are both available.
The LWS control system features a complete graphical user interface (GUI) at the top level which interacts with the instrument via a keyword interface. The keyword system follows the standard Keck architecture that allows the user to inquire and manipulate the instrument and telescope from the command line. The GUI includes an IDL-based ``quicklook'' image display and analysis tool, plus other windows which control the instrument and telescope configuration (e.g., chop-nod frequency and throw).