Thunderstorm III 4-megahertz burst-mode data acquisition system

Experimental results from many platforms indicate strong coupling between lightning and the ionosphere and show the necessity of high-frequency sampling in future experiments. We describe the lightning-triggered, burst-mode data acquisition algorithm and circuit used in the NASA sounding rocket 36.111, which is scheduled for launch in 1995. Burst-mode acquisition increases the time resolution by almost two orders of magnitude over that of continuous sampling, but requires a smart controller to select important data. The increase in time resolution will yield sounding-rocket electromagnetic-wave data valid up to the plasma frequency for the first time in the lightning environment. The instrument samples the vector electric field and one component of the magnetic field at 4 MHz with 10-bit, resolution, yielding a burst rate of 320 Mbits/s. Burst-mode instruments use ground commands, precursors, or recorded preburst data to ensure the proper data are recorded.