High resolution Michelson interferometer for airborne infrared astronomical observations. 2: System design

A Michelson interferometer for high resolution (lambda/Deltalambda approximately 10(4)) spectroscopic observations of astronomical ir ionic line emission has been built and flown on the NASA 91-cm airborne ir telescope facility (G. P. Kuiper Airborne Observatory). In Part 1 of this paper the requirements for such a system were outlined, and the scientific basis for the choice of instrumental parameters and the rapid scan mode of operation were discussed. In this paper design details of the instrument are presented. These include the optics, control He-Ne laser interferometer, helium-cooled bolometer detector, and cooled passband filters. In addition, the on-line computer software which enables the operator to interact rapidly with the system to produce inflight spectra and control accordingly the observational parameters is described, as are elements of the electronics hardware developed specially for airborne observations.