W. M. Keck Observatory
LWS Home Page

Observer Hot Links

Web Site Contents

Proposal Information
Sensitivities, Time estimates, instrument specifications
Observer's Guide
Handbook of LWS usage
Technical details on LWS capabilities
Step-by-step instructions for every observing phase
Keck Computing & Networking
Computers available, CD / DVD backups, FTP procedure
Telescope & Facility Data
Telescope information, site data, weather links
Diagnosing and fixing problems, getting help
Night sky line plots, standard stars, focus procedures
Technical Manuals & Data
Crate manuals, engineering drawings, photos
Instrument Procedures
Descriptions of maintenance and recovery actions
Keyword document and other LWS reference materials
VSQ Rooms, Post-Observing Comments, etc.
Documents, procedures, and tips for instrument scientists and technicians.
With links to every page

PSF Surface Plot

About the Keck Long Wavelength Spectrometer (LWS)

LWS is a Keck facility instrument offering diffraction-limited imaging and spectroscopy in the 3-25 µm range from the forward Cassegrain focus on Keck I. The instrument is currently being recommissioned following the installation of a new detector, a Boeing 128² Si:As moderate-flux BIB array.

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).

Go to: Instruments Home Page - Keck Home Page

Last modified: Tue Jan 29 17:19:37 HST 2002