|
A limb-viewing spatial heterodyne interferometer is developed to observe temperature in the mesosphere and lower thermosphere. This can be used to measure atmospheric waves with small vertical wavelengths. The instrument measures the O2 atmospheric A-band airglow emission in the near-infrared. The emission is visible during day- and night-time, allowing for a continuous observation. The image is taken by a 2d detector. The optical system conserves the 2d spatial temperature information. The spectral information is superimposed in horizontal detector direction. The usual processing thus uses the horizontal detector dimension to resolve the spectral while averaging the underlying spatial information. The altitude coverage is given by the vertical detector direction, resulting in a finely resolved vertical temperature profile for one image. In light of this, we explore a novel processing approach that exploits the spatial information along the horizontal axis as well. We propose to split the interferogram into two halves, mirror it around the center and perform a retrieval on both sides separately, obtaining two spatial cross tracks of independent temperature data. Assuming that the instrument views backward, consecutive measurements give along track sampling. Combining this with the split interferogram method and the usual fine vertical resolution of the instrument, it provides 3d information on the atmospheric temperature field which allows to obtain some information on 3d propagation characteristics of atmospheric waves. In our research, we delve into the viability, advantages and constraints of the split interferogram approach. We will discuss the impact of horizontal temperature variation onto the retrieval result. We show the impact of background temperatures on the retrieval. Furthermore, we discuss the influence of apodization onto the retrieval of split interferograms.
|
