Radar measurements of the reentry of the ariane 504 EPC

Abstract

A new VHF radar system has been integrated onto a KC-135 aircraft to provide a mobile platform for observing reentry of the Ariane 5 Main Cryogenic Stage (EPC). This system was flown successfully in performing measurements of reentry of the EPC from the Ariane 504 launch occurring on December 10, 1999. The primary requirement was to obtain the altitude of breakup of the EPC. Secondary requirements were to characterize the breakup, including searching for debris that might survive reentry, and to provide data on the reentry trajectory. Breakup was observed to begin somewhat above 70 km altitude, with evidence that fragmentation of the main structure continued over an 8 second interval, making the process somewhat higher in altitude than observed for Ariane 503. Multipath interference was observed in the long pulse transmission mode, and these data were used to obtain a direct measurement of EPC altitude as a function of time. This paper discusses the underlying concepts that contributed to planning the data acquisition and presents results of those measurements. This paper also discusses the data and data processing, leading up to a discussion of the results and lessons learned during the data reduction and analysis process.