HR: 0830h
AN: U31B-0001    [PDF]
TI: Infrasound Signals from the Space Shuttle Columbia
AU: * Herrin, E T
EM: herrin@passion.isem.smu.edu
AF: Southern Methodist University, PO Box 7503975, Dallas, TX 75275
AU: Negraru, P T
EM: negraru@passion.isem.smu.edu
AF: Southern Methodist University, PO Box 7503975, Dallas, TX 75275
AU: Mckenna, M
EM: smckenna@mail.smu.edu
AF: Southern Methodist University, PO Box 7503975, Dallas, TX 75275
AB: Infrasound signals from the shuttle Columbia were observed at the TXAR infrasound array on 1 February 2003. TXAR is in far Southwest Texas about 6oo km south of the shuttle's track across the panhandle of Texas. The signals were compared with those from STS 78 (7 July 1996) which had on almost identical track to Columbia (STS 107). Whereas the STS 78 signals had the characteristics of acoustic arrivals from a decaying N-Wave, the signals from STS 107 showed a number of sharp peaks superimposed on a background similar to the STS 78 data. Using a cross-correlation method, we estimated the back azimuths for eight of the peaks, and they agreed within $\pm$1 degree. We thus concluded that the peaks were multiple arrivals from a single explosive source. By crossing the mean back azimuth with the well known track of STS 107 we were able to determine the following parameters for the explosion. Location : 33.85 N, 101.92 W $\pm$20 km Time: 13 56.65 Z $\pm$ 0.1 min Height: 63.3 km Speed: Mach 16. Z Having the source location and time we were able to simulate the signals expected at TXAR using the InfraMAP program from BBN. This simulation showed arrivals that agreed with several of the observed impulsive signals to within a few seconds out of a total travel time of about 2000 seconds. The yield of the explosion was estimated using on AFTAC empirical formula based upon the dominant period of the signals, corrected for the elevation of 63.3 km. The estimated yield is 2 lbs. (0.9 kgm) HE (TNT). Because the signal to noise ratios for the observed arrivals at TXAR were large, we conclude that rocket experiments at White Sands involving explosions with yields of the order of 10 lbs at a height of 60 km should provide controlled infrasound sources that could be observed at a number of infrasound arrays.
DE: 9800 GENERAL OR MISCELLANEOUS
SC: U
MN: 2003 Fall Meeting