How many times has it happened? An instrumentation cameraman takes a selection of still cameras from the controlled environment of a calibration lab to a research test site in the dry desert or a humid swamp to record a still sequence of a one-of-a-kind test. Each camera is carefully set up and checked out, protected from the elements and triggered at the proper moment. Yet the lab results indicate that one or more of the photographs are overexposed and the image is smeared. Critical data is lost or marginal and there is no possibility of retakes. The loss can be measured in the thousands of dollars.
The data recording of storm information as detected by a weather radar has been customarily made on photographic film. Research radars and an occasional U. S. Weather Bureau radar are fitted with scope cameras to record the radar plan position indicator (PPI) display. Over the past 15 years a large sample of weather radar data has been accumulated in this fashion. The photographic technique provides an easy, quick, and inexpensive way to record weather radar data. The major drawback of this technique is data reduction. Information on storm shape, size, and intensity is normally extracted from the photographic images by hand. This means that only the most interesting aspects of individual storms are analyzed and the vast majority of the collected radar data is not analyzed. A vast amount of climatological information could be obtained from the existing store of weather radar data if an automatic technique of data retrieval were available. The first part of this report describes the use of a computer-controlled programmable film reader to process weather radar PPI photographs to obtain digital maps of rainfall intensity for use in climatological studies.
The basic physical quantity measured by earth resources survey optical instrumentation is the average scene spectral radiance in a field-of-view patch, modified by atmospheric transmittance. Often this spectral radiance is integrated over a band of wavelengths; the sensor then yields a band average of spectral radiance. Primary additional information is contained in the spatial distribution of this radiance, i.e., the scene geometry, and the time of day and year of the scene record. These statements apply to the broad class of photoelectronic imaging systems, including emulsion, photocathode, photovoltaic, and photoconductive sensors in a variety of scanning and non-scanning instruments.
In December 1968 Varo, Inc. began predelivery evaluation of an airborne night vision system (NVS) that we developed for the U. S. Air Force. A major performance factor that had to be measured was the maximum range (RMAX,)at which the NVS operator could acquire a target on the terrain under varying conditions of darkness and background contrast. This paper describes the restraints encountered in measuring (RMAX.) and the approach that was finally derived for doing so with the required high precision. At this writing, NVS details including performance such as (RMAX.) remain DOD classified. Consequently, data provided herein do not include the dimensions of targets that were acquired. Therefore, the values that can be calculated from those data given should not be construed as absolute.
As an introduction to the subject of gasdynamic lasers, I would like to discuss briefly some of the fundamental limitations on the average power output of laser devices. The most fundamental limitation on the average power output of a laser is the removal of waste energy resulting from the inefficiency of a laser. This waste energy may appear in the form of excited metastable states or simply as heat. In Figure 1 an analysis of various methods for removal of this waste energy are examined. Most laser devices, whether solid or gas, have an active medium of the form of a long, thin cylinder. With no flow or very little flow waste energy is removed by diffusion to the outer surface of the cylinder. In the case of a solid it is simply heat conduction to the wall where it is removed by a coolant; in the case of a gas laser, it is diffusion of metastable states or heat to the outer walls of a cylindrical container.
In its continuing efforts to meet the needs of the readership of the Journal of the SPIE the editorial advisory group has asked me to organize a book review section. Here is the first session on my own, I don't anticipate that this will continue since I expect to request reviews from a wide variety of people. Two conference proceedings are reviewed here, both of which are from the United Kingdom. Any interpretation of this as an attempt to wave the Union Jack is purely conicidental!