Overview of Venus orbiter, Akatsuki

Abstract

The Akatsuki spacecraft of Japan was launched on May 21, 2010. The spacecraft planned to enter a Venusencircling near-equatorial orbit in December 7, 2010; however, the Venus orbit insertion maneuver has failed, and at present the spacecraft is orbiting the Sun. There is a possibility of conducting an orbit insertion maneuver again several years later. The main goal of the mission is to understand the Venusian atmospheric dynamics and cloud physics, with the explorations of the ground surface and the interplanetary dust also being the themes. The angular motion of the spacecraft is roughly synchronized with the zonal flow near the cloud base for roughly 20 hours centered at the apoapsis. Seen from this portion of the orbit, cloud features below the spacecraft continue to be observed over 20 hours, and thus the precise determination of atmospheric motions is possible. The onboard science instruments sense multiple height levels of the atmosphere to model the three-dimensional structure and dynamics. The lower clouds, the lower atmosphere and the surface are imaged by utilizing nearinfrared windows. The cloud top structure is mapped by using scattered ultraviolet radiation and thermal infrared radiation. Lightning discharge is searched for by high speed sampling of lightning flashes. Night airglow is observed at visible wavelengths. Radio occultation complements the imaging observations principally by determining the vertical temperature structure.

Radio occultation experiment of the Venus atmosphere and ionosphere with the Venus orbiter Akatsuki

“…The advantage over the previous missions is the nearequatorial orbit of the spacecraft and a suite of multiband cameras dedicated to meteorological study (Nakamura et al, 2007(Nakamura et al, , 2011. The planned orbit around Venus is a 30 hour-period elliptical orbit near the ecliptic plane with the periapsis latitude of ∼10.5…”

“…The Radio Science experiment (RS) in the Akatsuki or Venus Climate Orbiter mission (PLANET-C project) of Japan Aerospace Exploration Agency (JAXA) will apply this technique to study the atmosphere of Venus (Nakamura et al, 2007(Nakamura et al, , 2011. Although radio occultation experiments have been conducted many times in the previous Venus missions, dense sampling at low latitudes and coordination with other measurements will enable a unique, efficient observation of the atmospheric structure and its temporal variation.…”

AKATSUKI returns to Venus

“…The scientific background for this research and data processing procedures are described in detail by Nakamura et al (2011Nakamura et al ( , 2014.…”

LIR: Longwave Infrared Camera onboard the Venus orbiter Akatsuki

“…These observations revealed a mean poleward flow with a velocity of up to 10 m s −1 at the cloud top. However, the limitation of the local time coverage may allow a significant contamination of the thermal tide component in the estimated meridional circulation, which can be as large as 10 m s −1 (Newman and Leovy, 1992). Characterization of the meridional circulation requires wind measurements at all local times.…”