Page 15 - April 2008

Table 1. Stations which participated in the WSMR infrasound calibration experiments.
ARDEC=Army Research, Development and Engineering Center, ARL=Army Research Laboratory, LANL=Los Alamos National Laboratory, Miltec=Miltec Corporation, SMU=Southern Methodist University, UA=University of Alaska, UCSD=University of California, San Diego, UH=University of Hawaii, UM=University of Mississippi
four hours apart. The Naval Surface Warfare Center group at WSMR was contracted to prepare and launch the rockets. The original intent was to detonate the charges at an altitude of approximately 50 km to maximize the long distance prop- agation of energy. The rocket design called for the explosive payload to detonate within the rocket, rather than being ejected prior to detonation. Thus, the explosion would result in the breakup of the rocket—the dimensions of the resultant debris pattern on the ground being a function of explosion altitude. Based on model results predicting the dimensions of the debris field, the initial WSMR explosions took place at roughly 30 km altitude. Empirical evidence gathered through the experiment permitted a gradual increase in the altitude of subsequent explosions. The final explosion of the six shots took place at about 49 km altitude.
The experiment utilized single-stage, rail-launched Orion rockets (Fig. 8). The rockets passed through a launch and a bal- listic phase, with the explosive charges detonated during the ballistic phase after the missile passed apogee (Fig. 9). All six of the detonations took place within a virtual “box” 20 km high, 9
km wide (east-west) and 24 km long (north-south), cen- tered at 40 km altitude at 33.175o N, and 106.515o W.
Preliminary estimates of the explosion parameters (time and altitude) were pro- vided by WSMR staff to infrasound team members who were present at the launch, and these estimates were relayed to participants in the field. After each exper- iment, WSMR personnel provided detailed radar data that gave three-component rocket position (latitude, lon- gitude and altitude), velocity, and acceleration as a function of time. The radar data were analyzed to pinpoint the det- onation coordinates. After analysis of the radar data, the remaining uncertainties in the explosion location and time were on the order of several kilometers and sever- al seconds, respectively. In addition, infrared cameras operated by M. Garcés (U. Hawaii) and by WSMR were used for two of the experi- ments to provide additional corroboration of launch and detonation times.
Observations
In the exploratory study of the data, basic observations about the spatial distribution of the recorded signals, and various parameters of the signals were made. It is these preliminary findings that will form the
basis of more in-depth analyses.
Fig. 6. Site view of station BACA, showing 60-m long optical fiber array elements.
Infrasound Calibration Experiments 13