Abstract: A present weather observing system including a radiation source for providing a beam of radiation in the atmosphere and a detector for detecting scattered radiation from suspended or precipitating particles within a sample volume, the detector having a field of view intersecting the beam to define the sample volume. The invention further includes a device for determining the size and velocity of at least one particle precipitating through the sample volume, and an element responsive to the device for determining size and velocity for identifying the type of precipitation.

Abstract: An instrument for responding to backscattered or backreflected radiation from a path through a medium in which a beam of electromagnetic radiation is transmitted along the path, and a receiver system is arranged to receive backscattered radiation returning along the path substantially coaxially with the beam, the receiver system including detection means for the backscattered radiation and equalizing means for producing a substantially equal response regardless of the point of backscatter along the path. The equalizing means comprises a passive radiation transmission structure interposed in the path of return prior to the detection means, the passive structure having a substantially constant acceptance solid-angle for the returning radiation from points over the range of the path whereby radiation reaching the detection means from various points along the path does not vary in intensity due to the different distances of the points from the detection means.