Using a geographical information system for monitoring space shuttle launches: Determining cumulative distribution of deposition and an empirical test of a spatial model
Space shuttle launches produce localized hydrochloric acid deposition. The interaction of solid rocket motor exhaust and deluge water released on the pad at the time of launch results in the formation of an exhaust cloud. The spatial pattern and extent of deposition from the launch cloud are predicted by the rocket exhaust effluent diffusion (REED) model. The actual pattern of deposition has been mapped by field surveys for each shuttle launch since 1981. In this paper we use a geographical information system (GIS) to compare model predictions with ground patterns for 49 shuttle launches. We also compile cumulative maps of deposition patterns needed to consider long-term impacts. The direction of launch cloud movement did not differ significantly from model predictions. The REED model overpredicted both the area that received deposition and the maximum distance from the launch pad that deposition occurred. Severe vegetation damage was restricted to near-field deposition areas within 1980 m north of each launch pad. Total area impacted from launches has been 87.0 ha around pad 39A and 52.9 ha around pad 39B. Far-field deposition has caused leaf spotting from acid droplets or aluminum oxide over a wider and more variable area than near-field. A total of 19,397 ha has received deposition, but 63.6% of this area has received deposition only one time and 92.2% not more than three times. GIS techniques provide means to test spatial models and compile information useful for assessing cumulative impacts.
Spotlight mode SAR stereo technique for height computation
This paper examines the feasibility of extracting three-dimensional (3-D) or topographic information in spotlight mode stereo synthetic aperture radar (SAR). A display of a SAR (intensity) image has two axes: range and cross-range. Elevated scatterers appear closer in range; this phenomenon is called radar image layover. How the height of each scatterer can be computed from the difference in its layover between two images is investigated. This is analogous to computing height from disparity distance (triangulation) in optical stereo. The same procedure can be applied on pixel by pixel basis for terrain elevation mapping. A general expression is derived for the accuracy of the height estimate as a function of the range resolution and the angular difference between the image planes. Accuracy increases as the angle between the image planes increases, but the bright scatterers in one image tend to fade in the other image. This limited angular persistence of radar scatterers is also discussed. Trajectories for data collection are examined that provide near-optimal height estimates while eliminating the scatterer persistency problem.
Aerosols and Trace Gases in the Effluents Produced by the Launch of Large Liquid- and Solid-Fueled Rockets
Abstract Airborne measurements over periods of several hours were made in the effluents that collected in the boundary layer in the form of “ground clouds” when an Atlas/Centaur and Titan III rocket were launched at night-time from Cape Canaveral, Florida. The ground cloud produced by the ATLAS was dry, whereas that produced by the TITAN was initially wet, then dry, and finally wet again. Both clouds dispersed primarily in the horizontal plane. Their volumes at time t (min) were given by V = V0tn where V0 = 1.3 × 106 m3 and n = 0.98 for the ATLAS and V0 &equals 1.76 × 107 m3 and n = 0.94 for the TITAN. The ATLAS ground cloud initially contained elevated concentrations of NO, N02, hydrocarbons and particulate mass. However, dispersion of the cloud quickly reduced these concentrations and the light-scattering coefficient of the cloud. Gas-to-particle conversion (postulated to be the result of the oxidation of NO to NO2 followed by the Formation of NH4NO3) produced smoke particles at a rate of - ∼1016 s−1 in...