Ground‐based observations of atmospheric density profiles to 92 km were obtained for four successive seasons between summer 1989 and spring 1990. These results were obtained with a powerful Rayleigh lidar facility located at Wright Patterson Air Force Base (Dayton, Ohio). This instrument combined a 14‐W XeF laser transmitter with a 2.54‐m receiver mirror to observe returns from altitudes between 40 and 95 km. Analysis of the scale height dependence of the density profiles produced temperatures with a measurement error of about 5 K (∼2.5%) at 90 km when the lidar data was averaged for 20 min. and smoothed in height over 2.7 km. Examination of these profiles for the total of 18 nights showed that there often existed in the mesophere a layer of enhanced temperatures when compared with the U.S. standard profile. The layer centroid height was about 85 km for summer and 70 to 75 km for winter. Data obtained for the equinoctial periods showed the amplitude of these layers to be weak. The winter temperature profiles showed evidence forlong‐period waves passing through the region of the thermal anomaly while the equinox profiles revealed more sporadic wave activity with shorter vertical wavelengths. Both the winter and summer temperature data displayed regions where the observed lapse rate approached the adiabatic lapse rate. In the summer the wave activity near the inversion layer was weak.

Diffusion of radon and thoron from the Ilunar surface provides a mechanism for production of a radioactive surface layer on the moon. If the radon and thoron flux from the lunar surface is equal to that measured at the earth's surface, the equilibrium activity of this surface layet is estimated as approximately 1 microcurie per square meter, due to radon and its decay products. This activity consists of alpha particles and gamnmna rays at well-defined energies and of beta rays.

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Design, construction, and testing of a photoelectronic UV-B personnel dosimeter whose optical system and thus wavelength and angular response match closely the Robertson-Berger sunburn ultraviolet meter is described. Erythema1 irradiance is sensed by a MgWO, fluor, and cumulative exposure is stored in digital form by custom-built hybrid microcircuits for readout through a microcomputer at a central station or a field display unit. Sensitivity and exposure storage capacity are designed to provide research-standard precision in measurements of a few hours to 5 2 months duration, and a high level of temperature stability has been achieved. The dosimeter's compactness, rugged and waterproof construction, and wide dynamic range make it applicable to laboratory and environmental photobiology research as well as in skin cancer epidemiology studies.

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