Physics of auroral phenomena : proceedings of the 35th Annual seminar, Apatity, 28 Februaru – 02 March, 2012 / [ed. board: A. G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2012. - 187 с. : ил., табл.

В. V. Kozelov et al. direction of observation. Usually the cameras arc directed to a region near magnetic zenith. The distance between the points of observation is 4120 m, so identical monochromatic cameras can be used as a stereoscopic system to resolve auroral structures at altitudes of 90-300 km. A special module was developed for precise synchronization of image capture by the cameras. The estimated precision of time synchronization for simultaneous images is better than a few milliseconds, which is a good precision for auroral observations. between observational points. Taking into account the elevation angle \|/ (between the directions to the satellite and to the horizon), we deduce for the considered event: H = d sin \|/ /sin a = 4.12 sin 76°/ sin 0.30° = 760±50 km This agrees quite well with typical altitudes of the IRIDIUM satellites. However the discrepancies are relatively larger due to too small distance between the cameras to resolve so large altitudes. Typical objects observed at smaller altitudes are meteors. Figure 3 presents an example of such meteor track. Reconstruction of the track geometry is shown in Figure 4. The altitudes 94-103 km are typical for small meteors. Note that the discrepancies of the altitude estimation in this region are ~1.5 km._____________ APB ■ , ■ -, . .„ ,: . - ■ii ' .Л ■ М.: ' ‘ ‘ ; • : - ; ■ ’ ' . / 1 , • APP Fig. 2. IRIDIUM-37 satellite observed by cameras Guppy-1 (APB) and Guppy-2 (APP). Exposition 1 s. One can see visual parallax of the satellite location against the background of stars. The satellite is a very sharp object, so from stereo pair of images the visual parallax can be estimated with sub-pixel precision. Our estimation is 7.5±0.5 pixels, which corresponds to a=0.30°±0.02° for angular resolution -0.04° per pixel. Then the distance from observational point to the satellite is d /sin a, where d = 4.12 km is distance 42 APP Fig. 3. Meteor track observed by cameras Guppy-1 (APB) and Quppy-2 (APP). Exposition 1 s. Meteor track, 2 0 1 1 /1 2 /0 3 23:37:52 UT 23 24 25 26 distance, km Fig. 4. Reconstruction of the meteor track by triangulation. Tests by sharp objects Auroral structures typically have smooth boundaries, therefore the triangulation abilities of the system have been tested by known sharp objects at different altitudes. Figure 2 demonstrate a bright flash of IRIDIUM-37 satellite observed by both cameras.