OPTICAL-DETECTION OF LIGHTNING ON VENUS

The night side of Venus was imaged at 18.8 frames per second using coronagraphic optics and a 153-cm telescope during the spring 1993 apparition in a search for lightning. The images were then reduced such that scattered light from the day side was removed and transient signals were sought. Several potential lightning flashes were detected at a wavelength near 777.4 mm. The six flashes were calculated to have optical energies ranging from 10(8) to 2 x 10(9) J. The detected hashes occur at a rate of 2.7 x 10(-12) km(-2) sec(-1). A single flash detected in control images yields a false rate 0.66 times the non-control rate; however, it now appears that the lightning spectrum contains a line in the wing of the ''control'' filter bandpass. We now believe this detection to be a valid lightning flash. A limit of detection is set at 5 x 10(6) J for 95% detection and 1.5 x 10(6) J for 50% detection. With this limit, it would have been possible to observe the brightest of Earth-like lightning should it exist on Venus. (C) 1995 Academic Press, Inc.