Doppler asymmetric spatial heterodyne (DASH) interferometry for simultaneous wind and temperature measurements of the thermospheric red (630 nm) and green (558 nm) lines

The Doppler Asymmetric Spatial Heterodyne (DASH) concept has been proposed to measure upper atmospheric winds and temperatures. The approach is identical to the concept of Spatial Heterodyne Spectroscopy (SHS) except one interferometer arm exhibits an additional optical path offset which optimizes the instrument for the measurement of atmospheric winds and temperatures. A DASH interferometer is a field-widened Michelson that utilizes diffraction gratings instead of mirrors to measure an interferogram over a large path difference interval without moving parts. This feature enables the instrument to simultaneously monitor multiple atmospheric lines and calibration lines to track instrumental drifts. It is a two-beam interferometer with greatly relaxed optical flatness and alignment requirements when compared to both the Fabry-Perot and Michelson. The DASH interferometer described in this paper utilizes multi-order diffraction gratings to simultaneously measure thermospheric winds and temperatures from the upper atmospheric red line at 630 nm and the green line at 558 nm. This paper will discuss the design of the interferometer and laboratory tests of a breadboard DASH that utilizes multi-order gratings.