THE BLAST WAVE OF THE SHUTTLE PLUME AT IONOSPHERIC HEIGHTS

The main engine burn (MEB) of the Space Shuttle deposits similar to 2x 10(12) joules of explosive energy and similar to 3x10(5) kg of exhaust in almost horizontal flight at 105-110 km altitude during the period 300-550 s into the ascent. This extremely robust perturbation provides a potential active-excitation source for a variety of geophysical pro cesses, including (1) the effects of aurora-like localized heating on the generation of gravity waves in the thermosphere, (2) the ducting m echanisms for long-period infrasound in the upper atmosphere, (3) dyna mo effects associated with transient charge separation, (4) interactio ns with ambient midlatitude current systems at E-layer heights, and (5 ) effects in the Earth-ionosphere waveguide of transient electron-dens ity perturbations in the D-region. The sine qua non of such an agenda is to gain a quantitative understanding of the nearfield behavior of t he MEB exhaust-plume's quasi-cylindrical expansion, which generates a blast wave propagating away from the explosion. We report on observed electron-density signatures of this blast wave as manifested on lines- of-sight (LOSs) from a very-long-baseline interferometer (VLBI) illumi nated by 137-MHz beacon signals from the MARECS-B satellite. We also c ompare the observations to a preliminary three-dimensional neutral-ah acoustic model coupled to the ionospheric electron density.