A statistical analysis was performed with use of Smithsonian Astrophysical Observatory's data on photographic meteors with use of weighting factors developed at Lewis Research Center for correction of various biases involved in meteor photography. The analysis used an armor damage criterion supplied by Ames Research Center. Although the analysis was restricted to Earth's orbit about Sun, implications are discussed regarding total population of meteoroids throughout the solar system. In Earth's orbit about the Sun, advantage was found for cylindrical armor extending in the solar direction and a plane sheet alined normal to apex of Earth movement.

February issue includes Appendix entitled Directory of United States Government periodicals and subscription publications; September issue includes List of depository libraries; June and December issues include semiannual index.

A cumulative list of works represented by Library of Congress printed cards.

Includes entries for maps and atlases.