Search

The design of cryogenic, scanning Fabry-Perot interferometers for the Long-Wavelength Spectrometer on the ESA Infrared Space Observatory is presented. The interferometers were designed to provide a spectral resolving power of [10.sup.4] over the wavelength range 45-180 [[micro]meter], with the highest possible transmission efficiency consistent with this requirement. Metal meshes, custom designed with the aid of a theoretical model of metallic reflection, were used as the reflecting elements. The scanning mechanism featured a spring-suspended plate, which was servocontrolled by moving coil actuators and monitored by capacitance micrometers. The spectroscopic performance of the interferometers was measured in the laboratory and is compared with the model developed for the interferometer design. Although the measured resolving powers were somewhat lower than expected because of the laboratory measurement conditions, the transmission efficiencies were in approximate agreement with the design specification. Key words: Infrared Space Observatory, Long-Wavelength Spectrometer, Fabry-Perot, infrared, spectroscopy, cryogenic, mesh, capacitance micrometer.

An optical alignment tool is described, which acts like an optical tee to produce two collinear beams whose direction can be adjusted. The device can be used to align optica subsystems.

A numerical method for eliminating channel spectra from data obtained with a bandlimited infrared Fourier transform spectrometer is developed. The method is compared with others in common use on a synthetic model spectrum.