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Author: Granzer, Thomas × Type: Article ×

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    Reflectivity of Venus’s Dayside Disk During the 2020 Observation Campaign: Outcomes and Future Perspectives
    ([Bristol] : IOP Publishing, 2022) Lee, Yeon Joo; García Muñoz, Antonio; Yamazaki, Atsushi; Quémerais, Eric; Mottola, Stefano; Hellmich, Stephan; Granzer, Thomas; Bergond, Gilles; Roth, Martin; Gallego-Cano, Eulalia; Chaufray, Jean-Yves; Robidel, Rozenn; Murakami, Go; Masunaga, Kei; Kaplan, Murat; Erece, Orhan; Hueso, Ricardo; Kabáth, Petr; Špoková, Magdaléna; Sánchez-Lavega, Agustín; Kim, Myung-Jin; Mangano, Valeria; Jessup, Kandis-Lea; Widemann, Thomas; Sugiyama, Ko-ichiro; Watanabe, Shigeto; Yamada, Manabu; Satoh, Takehiko; Nakamura, Masato; Imai, Masataka; Cabrera, Juan
    We performed a unique Venus observation campaign to measure the disk brightness of Venus over a broad range of wavelengths in 2020 August and September. The primary goal of the campaign was to investigate the absorption properties of the unknown absorber in the clouds. The secondary goal was to extract a disk mean SO2 gas abundance, whose absorption spectral feature is entangled with that of the unknown absorber at ultraviolet wavelengths. A total of three spacecraft and six ground-based telescopes participated in this campaign, covering the 52–1700 nm wavelength range. After careful evaluation of the observational data, we focused on the data sets acquired by four facilities. We accomplished our primary goal by analyzing the reflectivity spectrum of the Venus disk over the 283–800 nm wavelengths. Considerable absorption is present in the 350–450 nm range, for which we retrieved the corresponding optical depth of the unknown absorber. The result shows the consistent wavelength dependence of the relative optical depth with that at low latitudes, during the Venus flyby by MESSENGER in 2007, which was expected because the overall disk reflectivity is dominated by low latitudes. Last, we summarize the experience that we obtained during this first campaign, which should enable us to accomplish our second goal in future campaigns.
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    Space Photometry with BRITE-Constellation
    (Basel : MDPI, 2021) Weiss, Werner; Zwintz, Konstanze; Kuschnig, Rainer; Handler, Gerald; Moffat, Anthony; Baade, Dietrich; Bowman, Dominic; Granzer, Thomas; Kallinger, Thomas; Koudelka, Otto; Lovekin, Catherine; Neiner, Coralie; Pablo, Herbert; Pigulski, Andrzej; Popowicz, Adam; Ramiaramanantsoa, Tahina; Rucinski, Slavek; Strassmeier, Klaus; Wade, Gregg
    BRITE-Constellation is devoted to high-precision optical photometric monitoring of bright stars, distributed all over the Milky Way, in red and/or blue passbands. Photometry from space avoids the turbulent and absorbing terrestrial atmosphere and allows for very long and continuous observing runs with high time resolution and thus provides the data necessary for understanding various processes inside stars (e.g., asteroseismology) and in their immediate environment. While the first astronomical observations from space focused on the spectral regions not accessible from the ground it soon became obvious around 1970 that avoiding the turbulent terrestrial atmosphere significantly improved the accuracy of photometry and satellites explicitly dedicated to high-quality photometry were launched. A perfect example is BRITE-Constellation, which is the result of a very successful cooperation between Austria, Canada and Poland. Research highlights for targets distributed nearly over the entire HRD are presented, but focus primarily on massive and hot stars.