Abstract. The Long-Wavelength Spectrometer (LWS) is one of two complementary spectrometers aboard the European Space Agency's Infrared Space Observatory 1 (ISO) (Kessler et al., 1996). It operates over the wavelength range 43 196:9 m at either medium (about 150 to 200) or high (6800 to 9700) spectral resolving power. This Letter describes the instrument and its modes of operation; a companion paper describes its performance and calibration.Send offprint requests to: P.E. Clegg (p.e.clegg@qmw.ac.uk) ? ISO is an ESA project with instruments funded by ESA Member States (especially the PI countries: France Germany, the Netherlands and the United Kingdom) and with the participation of ISAS and NASA.
This book provides an informative account of the design of instruments used in rockets and spacecraft. The volume begins with a chapter introducing the basic principles of designing for the space environment. Following chapters discuss mechanical, structural, thermal and electronic design including the problems that are frequently encountered in the testing and verification of spacecraft subsystems. Important topics are described, including stress analysis, multilayer insulation, two-dimensional sensor systems, mechanisms, the structure of space optics, and project management and control. A final chapter looks towards future developments of space instrument design and addresses issues arising from financial constraints. The book contains lists of symbols, acronyms and units and a comprehensive reference list. Worked examples are found throughout the text. This volume is suitable for researchers and engineers in spacecraft and space instrument design. It will also be valuable to graduate students of physics, space science, spacecraft engineering and astronautics.
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(4) over the wavelength range 45-180 µm, 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.
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