Ionospheric Shock Front from Apollo 15 Launching

IONOSPHERIC perturbations observed at Fort Monmouth, New Jersey, over a distance of more than 1,200 km following the launch of Apollo 14 were attributed1 to the arrival of an atmospheric shock front which splits2 at ionospheric heights into ion acoustic and normal acoustic modes. An opportunity to repeat these observations was provided by the launching of Apollo 15 on July 26, 1971, at 0834 EST. Ionograms were taken at our station (74: 07:52 W longitude; 40:23:25 N latitude). Ionograms taken simultaneously at Wallops Island (75:29 W longitude; 37:51 N latitude) were made available by courtesy of National Oceanic and Atmospheric Administration (NOAA). We converted all ionograms to true-height.