Imaging atmospheric winds and temperatures with optical Doppler Michelson interferometry: high-resolution spectroscopy at small optical retardations

Abstract

ABSTRACT The need to measure upper atmospheric winds has led to the development of solid glass field-widenedimaging Michelson interferometers that operate at a fixed path difference. This approach may bedescribed as Doppler inrferometry or phase stepping interferometry . It has culminatedill the flight of WINDII, the WIND Imaging Interferometer on NASA's Upper Atmosphere ResearchSatellite. 1. BACKGROUND The electro-optical revolution that began in 1957 at the Laboratoire de Bellevue with Lcs ProgrsR(ccnts en spectroscopie interferentielle produced a number of photoelectric interferometers. Up-per atmosj)heric scientists were quick to realize the potential of the Fabry-Perot spectrometer formeasurement of temperature from Doppler line widths of atomic oxygen emission in airglow.Sputnik I was also launched in 1957 but it was a long time before in-situ measurements of upperatmospheric ternj)erature were made, and in the interim, ground-based optical remote sensing of tern-perature from airglow became productive. Rocket and satellite measurements became commonplacelater, but the optical method was then extended to remote sensing of atmospheric temperatures andwinds from satellites flying above.Dr. Herbert Gush's experience with Michelson interferometers for airglow observations led theauthor to believe that a Michelson interferometer could be more powerful than the Fabry-Perot spec-trometer for line width measurements. The way to achieve this was found during a visit to Bellevuein 1961, where a field-widened Michelson interferometer was being constructed by Ovd Harang, ayoung Norwegian scientist, in collaboration with Pierre Connes, to take visible region spectra of theaurora borealis. These results were never forthcoming, but this field-widened instrument opened thepathway to what may he called Optical Doppler Imaging.