NASA Scientific and Technical Aerospace Reports

20040073763 Georgia Tech Research Inst., Atlanta, GA
Mitigation of Atmospheric Effects on Imaging Systems
Gimmestad, Gary G.; Belen’kii, Mikhail S.; Mar. 31, 2004; 27 pp.; In English; Original contains color illustrations
Contract(s)/Grant(s): DAAD19-00-1-0503
Report No.(s): AD-A422695; ARO-40432.1-C1; No Copyright; Avail: CASI; A03, Hardcopy
Atmospheric effects such as refractive turbulence and aerosol obscuration can seriously degrade the performance of
military optical systems. A complete understanding of these effects is therefore essential for optimizing the design of such
systems, and it is also necessary for developing mitigation techniques. The project described here was a three- year theoretical
and experimental investigation to develop and validate a physical understanding of several atmospheric effects that are
important for current and future Army optical systems. a) An investigation of turbulence-induced waviness in images of edges,
and techniques for its mitigation. b) An investigation of the degradation of optical images by atmospheric turbulence and a
validation of the predicted dependence of the atmospheric Modulation Transfer Function (MTF) on the inner scale of
turbulence.
DTIC
Atmospheric Effects; Atmospheric Refraction; Images; Imaging Techniques; Optical Equipment; Optical Radar; Refractivity
20040073817 Science Applications International Corp., San Diego, CA
Analysis and Simulation of Cavity-Decoupled Chemical Explosions
Stevens, J. L.; Rimer, N.; Xu, H.; Murphy, J. R.; Barker, B. W.; Baily, E.; Oct. 24, 2003; 48 pp.; In English; Original contains
color illustrations
Contract(s)/Grant(s): DTRA01-01-C-0069; Proj-DTRA
Report No.(s): AD-A422856; SAIC-03/2050; AFRL-VS-HA-TR-2004-1030; No Copyright; Avail: CASI; A03, Hardcopy
We analyze data from two sets of decoupled chemical explosions. NORSAR has obtained data from seven decoupled
chemical explosions conducted from 1987-2002 in Alvdalen, Sweden, recorded both in he near field and on regional seismic
stations NORES, HAGFORS, and NORSAR. The explosions were conducted in three granite chambers at a depth of
approximately 100 meters in chambers with volumes of 200, 300 and 1000 m and yields ranging from 2500 kg to 10,000 kg.
The smallest explosion in the largest chamber is almost fully decoupled while the other explosions are partially coupled,
overdriven by up to a factor of 25. The data show that decoupling remains fairly constant for overdrive up to about a factor
of 10, then decreases rapidly at higher yields. 1D and 3D simulations of these explosions are performed to model the data.
IDG has digitized a set of surface seismic data recorded from a series of Soviet high-explosive cavity decoupling tests
conducted in a mine in Kirghizia in the summer of 1960.
DTIC
Cavities; Chemical Explosions; Explosions; Simulation
20040073820 Science Applications International Corp., San Diego, CA
Improved Focal Depth Determination for Use in Seismic Monitoring of the Underground Nuclear Explosions
Murphy, J. R.; Barker, B. W.; Marshall, M. E.; Rodi, W. L.; Nov. 19, 2003; 60 pp.; In English
Contract(s)/Grant(s): DTRA01-01-C-0056; Proj-DTRA
Report No.(s): AD-A422863; AFRL-VS-HA-TR-2004-1031; No Copyright; Avail: CASI; A04, Hardcopy
Seismic event location remains as one of the most important discriminants for separating natural tectonic and explosive
events. For example, it has been estimated that approximately 8O%of known global earthquakes have focal depths greater than
50 km or are located more than 25 km at sea. Since underwater nuclear explosions can be confidently identified to very low
yields using hydroacoustic data, it follows that the vast majority of earthquakes can potentially be identified on the basis of
location alone. This is an important observation since global monitoring of underground nuclear testing may require the
screening of tens of thousands of seismic events per year and, in order to perform this function efficiently, it will be necessary
to have simple and robust discriminants available which can be used to eliminate the vast majority of these events from more
detailed consideration. However, in order to be useful for such discrimination purposes, the uncertainties associated with
seismic locations must be well defined and reliable and this has proved to be difficult to accomplish.
DTIC
Depth Measurement; Nuclear Explosions; Seismology; Underground Explosions
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