This is the fourth in a series of reports on research at the Air Force Cambridge Research Laboratories. The report covers a two-year interval, as will succeeding reports in this unclassified series. This report was written primarily for Air Force and DoD managers of research development--and more specifically, for the managers in our Headquarters office, the Office of Aerospace Research. But it is hoped that it will be of interest and value to a much broader audience. To encompass this broader audience and to make the content more meaningful, the report attempts to relate, by means of survey discussion, the programs to the larger scientific field of which they are a part. The work of each of the nine laboratories is discussed separately in chapters with an overall introductory chapter on AFCRL management and logistic activities during the reporting period. (Author)

Summaries are given of research in the following fields: upper atmosphere physics, microwave physics, space physics, terrestrial sciences, optical physics, data sciences, meteorology, solid state, aerospace instrumentation.

The bibliography of AFCRL in-house technical reports lists all reports issued in the existing series. In addition, appendices list reports issued from 1962 to 1964 when series designations were not used, and reports issued in now-defunct series.

This bibliography lists all AFCRL in-house reports, journal articles, and contractor reports from 1 October to 31 December 1969. Abstracts are included.

A summary of the space science activities of the Air Force Cambridge Research Laboratories (AFCRL) in 1971, including rockets, satellites, and balloons launched, results of experiments associated with the measurement and study of energetic particles and magnetic fields, upper atmosphere physics, ionospheric physics, geodesy, and optical physics, and experiments planned for 1972, are included. The definition of space science for the purpose of this report is limited to in-situ observations and measurements using the broad definition of space.