Chromatic refraction with global ozone monitoring by occultation of stars. I. Description and scintillation correction.

We describe refractive and chromatic effects, both regular and random, that occur during star occultations by the Earth's atmosphere. The scintillation that results from random density fluctuations, as well as the consequences of regular chromatic refraction, is qualitatively described. The resultant chromatic scintillation will produce random features on the Global Ozone Monitoring by Occultation of Stars (GOMOS) spectrometer, with an amplitude comparable with that of some of the real absorbing features that result from atmospheric constituents. A correction method that is based on the use of fast photometer signals is described, and its efficiency is discussed. We give a qualitative (although accurate) description of the phenomena, including numerical values when needed. Geometrical optics and the phase-screen approximation are used to keep the description simple.

Chromatic Refraction with Global Ozone Monitoring by Occultation of Stars. II. Statistical Properties of Scintillations.

The statistical properties of stellar scintillations are discussed with special attention to correcting the atmospheric transmittance data for scintillations in measurements made with the Global Ozone Monitoring by Occultation of Stars (GOMOS) instrument. Both anisotropic and isotropic turbulent inhomogeneities are taken into account. Calculated rms scintillation reaches several percent for altitudes of 30-35 km, an amplitude comparable with the expected absorbing features. Estimates of cross-correlation functions show that the GOMOS correction procedure can be applied efficiently for scintillations caused by anisotropic inhomogeneities, in contrast to the isotropic case. Some recommendations are given for conditions of observations with which to make better corrections of scintillations.

Use of polarization in interferometry after double passage through turbulence.

We report what are to our knowledge the first experimental results of coherence enhancement that use polarization to separate coherent and incoherent paths.