AKATSUKI returns to Venus

The AKATSUK Venus Climate Orbiter returned to Venus in December, 2015.

(Guest post by Hirokuni Oda, of Earth, Planets and Space.)

AKATSUKI is the Japanese Venus Climate Orbiter that was designed to investigate the climate system of Venus. The orbiter was launched on May 21, 2010, and it reached Venus on December 7, 2010. Thrust was applied by the orbital maneuver engine in an attempt to put AKATSUKI into a westward equatorial orbit around Venus with a 30-h orbital period. However, this operation failed because of a malfunction in the propulsion system. After this failure, the spacecraft orbited the Sun for 5 years.

View of AKATSUKI equipped with the five photometric sensors; a 1-μm infrared camera (IR1), 2-μm infrared camera (IR2), ultraviolet imager (UVI), long-wave infrared camera (LIR), and lightning and airglow camera (LAC).
View of AKATSUKI equipped with the five photometric sensors; a 1-μm infrared camera (IR1), 2-μm infrared camera (IR2), ultraviolet imager (UVI), long-wave infrared camera (LIR), and lightning and airglow camera (LAC).

On December 7, 2015, AKATSUKI once again approached Venus and the Venus orbit insertion was successful, whereby a westward equatorial orbit with apoapsis of ~440,000 km and orbital period of 14 days was initiated. Now that AKATSUKI’s long journey to Venus has ended, it will provide scientific data on the Venusian climate system for two or more years. For the purpose of both decreasing the apoapsis altitude and avoiding a long eclipse during the orbit, a trim maneuver was performed at the first periapsis. The apoapsis altitude is now ~360,000 km with a periapsis altitude of 1000–8000 km, and the period is 10 days and 12 h.

In the Frontier Letter by Nakamura et al. (2016) recently published for journal Earth Planets and Space (EPS), the followings are described; i.e. the details of the Venus orbit insertion-revenge 1 (VOI-R1) and the new orbit, the expected scientific information to be obtained at this orbit, and the Venus images captured by the onboard 1-µm infrared camera, ultraviolet imager, and long-wave infrared camera two hours after the successful initiation of the VOI-R1. Up-to-date brilliant Venusian images/movies with dynamic clouds could be viewed at AKATSUKI Special Site (in Japanese) of ISAS/JAXA. A series of scientific results on the Earth’s twin planet will follow.

Modified from the abstract of Frontier Letter “AKATSUKI returns to Venus “ (Nakamura et al., 2016) published on EPS.

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