Ground-based satellite-type images of the upper-atmosphere emissive layer.
With the introduction of infrared (IR) retina sensors used as focal-plane arrays in large telescopes, astronomical observations are now frequently located in the near-IR part of the spectrum. In this region the upper atmosphere introduces in the 0.7-3 microns range an additional component due to the OH vibrational band emission that should be subtracted from the astronomical data. Observations of this upper-atmosphere emission performed at the Pic de Châteaurenard (altitude of 2989 m) are presented here. A panoramic image of the emission is constructed by use of a set of 48 images obtained with a CCD camera mounted on an alt-azimuthal platform. After a numerical filter is used to suppress the star images, the atmospheric emission shows two distinct sets of arches vanishing at two opposite points in the WNW and ESE azimuths. The emissive layer, caused by the ozone-hydrogen reaction, is thin and located at the altitude of 85 km. By use of these data, the perspective effect that produces the panoramic arches is inverted in introducing the concept of a virtual camera. The Van Rhijn effect and the refraction correction are taken into account. The three punctual transformations that use matrix algorithms are analyzed. The result is a satellite-type view of the emissive layer that appears as a disk having a radius of approximately 1100 km. This disk is limited by the summit line of the Alps surrounding the Pic de Châteaurenard. The field of view covers a large part of Europe, the Mediterranean Sea, and North Africa. It shows an extended wave system. The images presented show that the upper-atmospheric layer is an efficient tracer of the dynamic processes at that level. Satellite-type views can be calculated without the drawback of looking downward from a satellite and measuring the numerous emissions from cities, oil fields, and other luminous sources.
Pautet
Dominique
D
Observatoire de Besançon, B.P. 1615, 41 bis avenue de l'Observatoire, 25010 Besançon, France.
Moreels
Guy
G