In-situ Turbulence and Particulate Measurements in Support of the BOLT II Flight Experiment

The results of a measurement campaign to characterize the free stream atmospheric turbulence intensity and particulate concentrations experienced by the BOLT II flight experiment are described. These measurements were obtained using custom high-altitude balloon-borne payloads using a modified commercial optical particle counter and a high-bandwidth coldwire thermometer and hotwire anemometer, designed for low cost and light weight, with telemetered data so that physical payload recovery is not necessary. Sixteen flights were carried out over a 10 day campaign, with viable data returned from 14, including 4 flights centered on the BOLT II launch with 1 hour cadence. Turbulence and particulate measurements are shown versus altitude for all 14 data sets, along with statistics derived from the measurements, quantifying the BOLT II atmospheric environment for use in assessing the impact of these free stream disturbances on the hypersonic vehicle boundary layer.