Invitation to the 2023 International Venus Observation Campaign

The Planetary Atmospheres Group (PAG) within the Institute for Basic Science (IBS) is conducting an atmospheric observation campaign for Venus 2023. The PAG-IBS team, led by Dr. LEE Yeon Joo, also invited an international team of telescopes to collaborate on data acquisition of the Venus disk from September to October 2023. This campaign will offer a unique opportunity to simultaneously study the atmosphere of Earth’s twin from three different locations in the solar system.

One of the main objectives of the mission is to solve the mystery of the ‘unknown absorber’ in the clouds over Venus. While Venus’ atmosphere is primarily composed of carbon dioxide (CO2), it exhibits significant absorption of solar radiation across a wide range of wavelengths, including the ultraviolet (UV) and visible (VIS) ranges. An unknown absorber in the atmosphere of Venus refers to an unknown substance or process that contributes to the absorption of solar radiation in the planet’s atmosphere.

The presence of this unknown absorber has intrigued astronomers for nearly a century since its first detection in ground-based UV images. Known absorbers in the Venusian atmosphere, such as sulfur dioxide, may explain some, but not all, of the observed near-UV and VIS absorptions. There are indications that other compounds or atmospheric processes are involved in the absorption of solar radiation, but their exact nature and composition are uncertain.

Another goal of the campaign is to explore the high variability of sulfur dioxide gas above Venus’ clouds, which have undergone drastic changes in their abundance in recent decades. These changes are thought to be related to surface volcanic activity on Venus. For example, active volcanoes have recently been identified using NASA’s Magellan data. Future Venus missions, such as EnVision and VERITAS, will search the surface for volcanoes more intensively.

For this campaign, an international scientific collaboration is being established with two ground-based spacecraft and telescope teams. So far, astronomers from South Korea, Japan, Spain, Germany, Switzerland and Russia have joined the project.

The study will utilize data obtained by the Akatsuki JAXA orbiter, which orbits Venus from 300,000 km away. In addition, ESA-JAXA’s BepiColombo Mercury mission will make remote observations of Venus in late September, during its voyage to Mercury. The BepiColombo UV spectrometer and the Akatsuki UV imager will observe Venus’ daylight disk. Such short-wavelength observations are only available from outer space, because Earth’s ozone layer prevents ground-based telescopes from obtaining UV data.

Meanwhile, the ground-based telescope team plans to acquire Venus data simultaneously in coordination with the two space missions. Ground-based data will complement spacecraft measurements which will provide a more complete picture of atmospheric conditions near cloud top levels. The overall data obtained from this campaign will cover a wide range of wavelengths, from near UV to near infrared, providing important information for scientific analysis of Venus.

This is a follow-up campaign after the previous one in 2020, and it is hoped that researchers will be able to achieve a better understanding of UV absorbers near the cloud-top level atmosphere on Venus.