Abstract: A lightning detection system utilizes a gated magnetic direction finder for determining the range and direction of lightning discharges to ground. Logic circuitry is provided for controlling gating circuits within the direction finder so that the direction measurement is made during the initial few microseconds of the return stroke waveform, thereby minimizing errors caused by nonvertical lightning channels to ground, branches and intracloud discharges. Distance measurements are made by analyzing the amplitude of the detected return stroke waveform, or by utilizing two or more geographically separated direction finders and triangulation techniques. The waveforms of the signals received by the direction finder are analyzed to determine whether the discharge is ground stroke or another type of discharge, or background noise. Further circuitry can be used to distinguish between various types of ground strokes, such as first strokes or subsequent strokes in a flash.

Abstract: The apparatus detects in real time the amplitude and range of certain traent events such as lightning discharges, the arrangement being such that a transient event which is capable of producing a return echo signal initially greater than other return signals is detected and the amplitude and range acquired in a manner which permits recording on moderate speed recording devices. A conventional sample and hold circuit acquires the range and its output gates a peak detector into "on" and "off" modes with the "on" period being centered about the range acquired by the sample and hold circuit. The "on" period is of relatively short duration and, importantly, the output acquired during the "on" period is held by the peak detector circuit until the initiation of the next transmitter pulse. The range output of the sample and hold circuit also is held for a predetermined length of time or until another transient event occurs. The `hold` periods permit the use of moderate speed recording devices.

Abstract: The apparatus is used primarily to monitor the occurrence of lightning diarges in the vicinity of a known objective such, for example, as a large rocket launch tower or other object which might be detrimentally affected by the lightning. A continuous, linear single-axis, position-sensing photodiode is deployed a predetermined distance from the objective and an optical objective lens focuses a relatively narrow field of view, such as a 40.degree. field on the photodiode. The arrangement is such that the image of a lightning discharge occurring within the field of view is in the form of a focussed narrow-line channel bisecting the length of the photodiode at varying locations dependent upon the actual location of the lightning discharges itself. In a conventional manner, the photodiode produces two signal outputs each corresponding in magnitude to the particular location of the bisecting channel image of the lightning. Using the fractional distribution of these signal outputs, the angle to discharge (.psi.

Abstract: A pair of position sensing photodiodes of a conventional quadrature or duaxis type are deployed face-upwardly at a predetermined distance one from the other. A vertically pointing fisheye lens covers each of the position sensing diodes so that the diodes view a full 360.degree. in azimuth and about 180.degree. in zenith angle. Each of the diodes produces four current outputs whose fractional distribution provides the location of the optical center of a luminous source, such as a lightning discharge. The outputs, in turn, are applied to a data acquisition system, such as a simple analog computer, which provides the location data for the lightning discharge as well as its total intensity. The circuit applying the outputs to the data acquisition system includes filtering means for eliminating background noises and passing to the system only the optical transients of the discharge.

Abstract: A pair of all-sky cameras each equipped with a 220.degree. Fisheye-Nikkor ns are disposed with their lenses pointing vertically. One of the cameras is rotated about an axis passing through the zenith while the other is maintained in a stationary disposition or, if desired, counter-rotated. Because of the relative rotational movement of the film of the cameras, there is a measure of displacement between the images formed on the respective films and the angular deviation produced by the displacement can be measured to determine the time development of lightning discharge.