The trace constituent reference models presented here are of trace species in the stratosphere, mesosphere and lower thermosphere which play important roles in controlling the chemistry, radiation budget and circulation patterns of the atmosphere.

Third edition of John Houghton's acclaimed textbook for advanced undergraduate/graduate courses in atmospheric science.

A knowledge of atmospheric density and its variation at satellite altitudes is needed for operational support of several military activities. Atmospheric density data computed from the decay rates of more than 40 satellites orbited during a five-year period were analyzed during this investigation. Multiple regression equations were derived to specify the density at 10-km intervals at altitudes from 180 to 300 km as a function of solar activity, time of day, time of year, and combinations of these variables. Density values depicted by these regression equations were then compared with density data which had not been used during the derivation of the equations. The results of this investigation indicate that multiple regression analysis and the associated screening procedure can produce equations from which computed density values are in close agreement with observed density data. The results lead to a conclusion that no single density model can meet all needs. These results also indicate that characteristics of a density model should be selected to fit the purpose for which the model is intended. Four possible density models designed for different purposes are suggested. (Author).

Roger D. Werking Head, Attitude Determination and Control Section National Aeronautics and Space Administration/ Goddard Space Flight Center Extensiye work has been done for many years in the areas of attitude determination, attitude prediction, and attitude control. During this time, it has been difficult to obtain reference material that provided a comprehensive overview of attitude support activities. This lack of reference material has made it difficult for those not intimately involved in attitude functions to become acquainted with the ideas and activities which are essential to understanding the various aspects of spacecraft attitude support. As a result, I felt the need for a document which could be used by a variety of persons to obtain an understanding of the work which has been done in support of spacecraft attitude objectives. It is believed that this book, prepared by the Computer Sciences Corporation under the able direction of Dr. James Wertz, provides this type of reference. This book can serve as a reference for individuals involved in mission planning, attitude determination, and attitude dynamics; an introductory textbook for stu dents and professionals starting in this field; an information source for experimen ters or others involved in spacecraft-related work who need information on spacecraft orientation and how it is determined, but who have neither the time nor the resources to pursue the varied literature on this subject; and a tool for encouraging those who could expand this discipline to do so, because much remains to be done to satisfy future needs.