Current Projects - J. R. Benbrook

Bob Sheldon and I were involved for the past several years in a collaboration put together by the Aerospace Corporation that included investigators from the University of Missouri at Rolla and from the Phillips Laboratory at Hanscom Air Force Base. Our ozone photometers, particle detectors from UMR, and a neutral mass spectrometer from Phillips were integrated into the WB57F high altitude research airplane operating out of Ellington Field adjacent to NASA/JSC. The ceiling altitude for this airplane is roughly 20 km, depending on air temperature and fuel load. This instrument complex was flown through the plumes of three Titan IV's, two Deltas, two Shuttles, and one Atlas during the period of our participation. Significant ozone destruction was observed during daylight flights in all cases. Models of the gas-phase chemistry that involve the chlorine introduced into the stratosphere by the solid rocket motors predict responses roughly in agreement with our observations, but the smaller boosters (Delta, Atlas) seem to have a disproportionately large effect. We did not participate in the 1999 activities of the group since our ozone instruments were replaced by other better(??) instruments from NOAA.

Gar Bering and I completed a campaign during the summer of 1999 in which three electric field balloon payloads were flown from southeastern Iowa to investigate sprites and blue jets above large thunderstorms in the midwest. These payloads contained search coil magnetometers, bremsstrahlung X-ray detectors, geiger tubes, and visible light detectors in addition to the usual double probe E-field detectors. The AC field data were sampled at a 50 kHz rate and a set of event triggers caused the on-board microprocessor to store appropriate segments of these data streams on a nvRAM pseudo disk for later analysis. We also had two telemetry links providing real time data at a lower sampling rate (1 kHz) on a pcm channel and four analog channels with 4 kHz bandwidth. The balloons were 1.5 million cubic feet in size and the launch operations were handled by a 13 man crew from the National Scientific Balloon Facility at Palestine, TX. Ground-based television monitoring of the atmospheric volume above the thunderstorm complexes were made from several high-altitude observatories located in the eastern rocky mountains. The results from the initial data analysis were presented to the 1999 fall AGU meeting in San Francisco. Follow-up papers were submitted to the 2000 fall AGU, but the amount of work done in the intervening year was small since we were not supported for the analysis. We have submitted two proposals to NASA for follow-on work, including repeating the field campaign to at least double our data bank.

During the 2002 and 2003 summers, I was fortunate enough to receive a Summer Faculty Fellowship appointment at Johnson Space Center, working with my ex-student, Gene Stansbery, on radar detection of orbital debris. During the 2002-3 academic year, I spent each Thursday at JSC, continuing to work on the radar problems. I plan to repeat that program during the upcoming 2003-4 academic year. My major area of focus is the apparent unphysical bias that appears in the trajectories of the detected debris particles. A large number of the particles are predicted to impact the solid earth in less than one orbit after observation. Suspect areas include the calibration procedures for the radar elevation and traverse angle offsets, as well as the calibration of the signal-to-noise ratio for off beamline observations.