Trial of the Sodium detection in the Lunar / Venusian atmosphere: Solar Eclipse (May 21) / Venus Transit (June 6)

We tried the detection of sodium in the Lunar and Venusian atmosphere by the absorption of Na DI (5895.92 A) during their transit on the solar surface occurred in 2012. Both observations were done by the 60cm Dome-less Solar Telescope (DST) of Kyoto University Hida Observatory. Lunar transit, i.e., the solar eclipse, occurred in 6:19-8:59 JST (93.3% eclipse at Hida) on 21 May 2012. It was find weather but at lower elevation angle, 18-50 deg. Venusian transit occurred 7:09-13:49 JST on June 6 2012. The elevation was enough, 29-76-60 deg, but the weather was not stabled. Venusian transit was also observed at Mt. Haleakala, by the Univ. Hawaii 50cm Solar telescope SOLAR-C. [The EUV observation by HINODE was also performed.] Both Hida observations were performed by the same settings. This telescope succeeded to detect Herman sodium atmosphere (Doppler shift: ~5 km/s, absorption: ~6%, column density: 6x10^10 /cm2) in the Herman transit on Nov. 9, 2006 [Yoshikawa et al., 2007]. This telescope has two spectrographs. In both observations, we used the Vertical Spectrograph with the wavelength resolution of 840,000 (7 mA) to obtain a long slit spectrum (slit width: 0.32 arcsec). We attached the Tohoku University CCD detector (Andor, 512x512 pixel), which achieved the field length of 52.5 arcsec (1 pixel: 0.1 arcsec) and the wavelength range of 1.58A (1 pixel: 3 mA). The lunar observation was executed not only for the rehearsal of the Venus observation but also aiming the first detection of low temperature sodium atmosphere nearby the surface. Na DI/DII emission lines have been observed by ground-based telescopes (incl. Tohoku Univ. 40cm telescope at Haleakala) and the Lunar orbiter Kaguya [Kagitani et al., 2010]. However, the distribution below the altitude of 10 km (corresponding to 5 arcsec in our observation) is hard to detect by the contamination of strong scattered light. We observed four points, dawn-side N20deg (mere), dawn-side S20deg (mountain), dusk-side N20deg (mountain), and dusk-side N0deg (mere), for 30 min each. Seeing was ~2-3 arcsec. Expected column density above 50km is ~1x10^9 / cm2 (absorption: ~0.1%) which is less than 1/10 of the Mercury case. In our tentative analyses, some spectra show ~2-3% excessed absorption below the altitude of ~20 km (~10 arcsec). However, solar Na DI absorption is not stable in time and space (variation: ~10-30% in maximum), and also has the Doppler changes (10s mA, several 100 m/s) by solar atmospheric turbulence. We are checking data set carefully. The Venus observation aimed the first detection of sodium in the Venusian upper atmosphere. The terrestrial sodium layer (2-5x10^9 /cm2) around 90km in altitude is maintained by the supply of interplanetary dust. At Venus, the dust supply from space would be twice of the Earth. However, the detection should be hard because the transmitting light through the Venusian atmosphere is mixed with the background sunlight. We used Tip-Tilt stabilization and achieved the seeing of 1-2 arcsec. But if it is 1 arcsec, the excess of the Na D1 absorption was only ~0.3%. In the tentative result, the Venus Na excessed absorption is less than 1%. It means that the Na in the Venusian upper layer is less than 3-4 times of the Earth's. It is consistent with our expectation.