Spatial and temporal variations of the atmospheric sodium layer observed with a steerable laser radar
LASER radar observations of resonance scattering from atmospheric sodium during the night have, on occasions, shown evidence of short term changes in the height distribution1–3. It has been suggested that these changes arise from the movement of a horizontally structured sodium layer, but the measurements have all been limited to the vertical direction, and have provided no direct evidence of a horizontal variation. Evidence of horizontal structure at mesospheric heights has been provided by observations of hydroxyl emissions in the airglow, both from the ground4 and from an aircraft5,6. In addition, the observed fluctuations of intensities and infrared rotational temperatures of the hydroxyl bands have been associated with the passage of atmospheric gravity waves7,8. We report here observations intended to examine the short term and small scale horizontal variations of the sodium layer which might also be associated with such waves.
Spatial and temporal filtering technique for processing lidar photocount data.
Shot noise places a practical limit on the spatial and temporal resolution of lidar photocount data. A 2-D signal-processing technique that utilizes spatial and temporal filtering to reduce shot noise and increase resolution is described. The technique is applied to sodium lidar data collected during the fall of 1979 over Urbana, Illinois. Temporal filtering is shown to enhance the spatial resolution of the sodium profiles significantly by reducing shot noise by more than 10 dB. The signal-processing technique is applicable to a wide variety of lidar data.
Experimental study of thermal modeling for stratospheric platform airships
R&D work on the Japanese stratospheric platform airship is discussed from the viewpoint of the thermal modeling. The work includes two experiments on the thermal characteristics of the 25m-long airship and the 35m-long PV-equipped airship model. The validity of the current thermal model was confirmed by comparing the calculated results with the measured data. The other important work is the Ground-to-Stratosphere (GTS) flight test. A 47mlong airship-shaped balloon was flown to the stratosphere. The flight simulation program into which the thermal model was integrated, was developed and applied successfully to predict the ascent behavior and the flight trajectory.