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We report spectroscopic measurements of sodium in Mercury's atmosphere for the period July 1985-May 1988. Na abundance varies from < 1 x [10.sup.10] atoms [cm.sup.-2] in equatorial regions in March 1987 to as much as ~1.5 x [10.sup.12] atoms [cm.sup.-2] in May 1988. All observations were made using a high-resolution echelle spectrograph on the 61-in. telescope on Mt. Bigelow, Arizona. Strong high-latitude enhancements are common, with the added characteristic that there is usually more at one hemisphere than the other. There is an obvious diurnal correlation, with morning abundances significantly higher than afternoon. We see notable Na emission enhancements when our spectrograph slit is placed over the radar-bright spots at 340 [degrees] mercurian longitude and 55 [degrees] N and 25 [degrees] S latitude. We do not see any trend in column abundance with increasing radiation acceleration. We do not see a significant correlation of abundance with either solar F10.7 flux or sunspot number. Other larger variations occur and must be caused by other factors.

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 nm. The six flashes were calculated to have optical energies ranging from [10.sup.8] to 2 X [10.sup.9] J. The detected flashes occur at a rate of 2.7 x [10.sup.-12] [km.sup.-2] [sec.sup.-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.sup.6] J for 95% detection and 1.5 X [10.sup.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.

Absorption spectra obtained by intracavity laser spectroscopy (ILS) often contain fringe patterns that significantly mask absorption features and hamper the quantitative analysis of ILS data. Both the parasitic etalon fringes and the fringes that originate from spatially localized losses can be suppressed by a low-amplitude audio-frequency vibration of a folding mirror in the laser cavity. Using this methodology, we show that ILS spectra recorded with multimode lasers that contain nonideal intracavity surfaces have essentially no fringe contamination. The elimination of fringe contamination improves the detection sensitivity of ILS under normal experimental conditions and thus expands the potential for ILS applications.

Atmospheric sodium and potassium on the Moon are analyzed. The results may be explained by a model of competing release mechanisms in which thermal desorption plays a major role. Atoms may be found at higher altitudes due to thermal desorption which imbibes the atoms with enough energy when they are on the surface of the Moon to attain the heights in which they are found. In cooler regions, there are less atoms within the same altitude. Sodium may be found in a region between 119 to 611 km above the surface and potassium may be found in a region between 85 and 154 km.