The use of GPS arrays in detecting shock-acoustic waves generated during rocket launchings

This paper is concerned with the parameters of shock-acoustic waves (SAW) g enerated during rocket launchings. We have developed the interferometric me thod for determining SAW parameters (including angular characteristics of t he wave vector, and the SAW phase velocity, as well as the direction toward s the source) using GPS-arrays. Contrary to the conventional radio-probing techniques, the proposed method provides an estimate of SAW parameters with out a priori information about the site and time of a rocket launching. The application of the method is illustrated by a case study of ionospheric ef fects from launchings of rockets PROTON, SOYUZ and SPACE SHUTTLE from Baiko nur and Kennedy Space Center cosmodromes in 1998-2000. In spite of a differ ence of rocket characteristics, the ionospheric response for all launchings had the character of an N-wave corresponding to the form of a shock wave. The SAW period T is 270-360 s, and the amplitude exceeds the standard devia tion of total electron content background fluctuations in this range of per iods under quiet and moderate geomagnetic conditions by factors of 2-5 as a minimum. The angle of elevation of the SAW wave vector varies from 30 degr ees to 60 degrees, and the SAW phase velocity (900-1200 m/s) approaches the sound velocity at heights of the ionospheric F-region maximum. The positio n of the SAW source, inferred by neglecting refraction corrections, corresp onds to the segment of the rockets path at a distance no less than 200-900 km from the launch pad, and to the rocket flying altitude no less than 100 km. Our data are consistent with the existing view that SAW are generated d uring a nearly horizontal flight of the rocket with its engine in operation in the acceleration segment of the path at 100-130 km altitudes in the low er atmosphere. (C) 2001 Elsevier Science Ltd. All rights reserved.