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Abstract. This paper describes results obtained using an automated, crystallographically-based technique for twin identification. The technique is based on the automated collection of spatially specific orientation measurements by electron backscatter diffraction (EBSD) in the scanning electron microscope (SEM). The key features of the analysis are identification of potential twin boundaries by their misorientation character, identification of the distinct boundary planes among the symmetrically equivalent candidates, and validation of these boundaries through comparison with the boundary and twin plane traces in the sample cross section. Results on the application of this technique to deformation twins in zirconium are analyzed for the effect of twin type and amount and sense of uniaxial deformation. The accumulation of strain tends to increase the misorientation deviation at least to the degree of the trace deviation compared with recrystallization twins in nickel. In addition to the results on characterizing the twin character, results on extending the twin analysis to automated identification of parent and daughter material for structures exhibiting twin deformation are reported as well.

Of the waves which propagate in the atmosphere at acoustic velocity in the period range from 10 to 100 s, one type has been classified by triangulation as arising principally from mountainous regions. These signals were first described as ' northwesters ' or ' 310 ers ' by the NBS Geoacoustics Group under R. K. Cook at Washington, D.C., from the predominant direction of arrival. Subsequent operation of an observatory at Boulder, Colorado by Vernon Goerke gave a source region by triangulation in the Pacific Northwest, primarily in Montana and Alberta. Installations of observatories at College, Alaska (Wilson) and Pullman, Washington-Moscow, Idaho (Craine and Thomas) enlarged the data base available, and triangulation showed the principal source areas to be along the coast of British Columbia and in the inland Rocky Mountains of the British Columbia-Alberta border. This paper discusses the presently known characteristics of this class of infrasonic waves, locates the triangulation areas, reviews selected events, and suggests that certain of these waves are produced as aerodynamic sound. The paper shows a correlation between the 500 mb jet stream velocity and direction in these mountainous regions, and the detection of these atmospheric pressure waves. Infrasonic waves-10to 100-s periodsThere are a number of atmospheric wave structures travelling at acoustic velocities that appear in the 10-to 100-s period range. An observatory, through four pressure sensitive transducers, provides basic information on the amplitude variations of pressure with time, from which the waveform, period, and time sequence of the event at an individual microphone can be obtained. By overlaying the charts and visually correlating the waveforms from several transducers, a signal can be identified in the noise, and arrival time differences measured. The azimuth of the direction of arrival, and the horizontal velocity across the transducer array, can then be calculated, assuming a plane wave. Detection of signals is often difficult, since local wind noise may obscure the desired signal, and changes in waveform caused by frequency dispersion of the signal or the effects of other signals arriving from different directions may make the waveform vary at each transducer. We define an ' event ' as a series of signals that appear to be related. 201 0 pr) FIG. 2. Correlation of mountain-associated waves at Pullman, Washington, at 1430 UT on 1968 November 28. Mean azimuth 329O, trace velocity 426 m s-l; approximate peak-to-peak amplitude 6 3 dyn cm-*; average period 50 s. facing page 202 Correlation of winds and geographic features 5 -203 15 10

One-Sentence Summary & Recommendation. Near-term, robust investigations of presentday impact flash and flux observations of the lunar surface would greatly benefit efforts to answer a number of important science questions, and more importantly, help quantify hazards that will be encountered by sustained robotic, human, and ultimately habitation endeavors on and below the lunar surface. Box 1-Priority science and exploration questions answered by impact flash and flux investigations and relative alignment with * SCEM & # LER documents.• How can we utilize the Moon as a natural laboratory to study impact flashes and the resulting craters to better inform laboratory experiments, numerical models, the cratering record, and ultimately the hazard they pose to sustained exploration? (SCEM 1c, 1e, 6d; LER Sci-A-7, B-1) • What is the present-day lunar impact flux and its range of meteoritic infall size? (SCEM 1c, LER Sci-B-1) • What does the present-day lunar impact flux imply about the impact flux at Earth and other bodies in the Solar System; particularly those of interest for human exploration (e.g., Mars)? (LER Sci-B-1) • What is the present-day spatial distribution of lunar bombardment? Does it vary temporally? Is the impact energy/flux higher on the Western (leading) or Eastern (trailing) hemisphere of the Moon relative to current models? Do the lunar poles incur the lowest impact flux? (SCEM 6c, 6d) • What are the geologic effects of present-day impact cratering on the Moon (e.g., resurfacing/gardening, seismic shaking, triggering of landslides, and range of influence)? (SCEM 6c, 6d, 7c; LER Sci-A-7, D-22, FF-C-1) • What volatiles are detectable in lunar impact plumes? If present, how are they redistributed, re-consolidated, and what percentage is lost? (SCEM 6c, 7c) • What can fresh exposures of new impact craters tell us about the physical nature of the lunar surface (exposure of volatiles, space weathering, layering/strength transitions...)? (SCEM 6c, 6d, and 7b, c; LER Sci-A-7) *Scientific Context for Exploration of the Moon; # Lunar Exploration Roadmap