Akatsuki Gets a Second Chance at Venus

A Japanese probe makes good on its plan to orbit another planet.

Akatsuki took this infrared image of Venus on its unplanned flyby five years ago. Better pictures to come. (JAXA)
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Japan’s space agency JAXA has successfully sent robotic spacecraft to explore the moon and asteroids, but until today, one goal had proven elusive—placing an orbiter around another planet. The Nozomi spacecraft launched in 1998 failed to reach Mars due to a propulsion problem, and the Akatsuki probe to Venus missed its target for the same reason in 2010. This morning, though, Akatsuki slipped into orbit around Venus, salvaging a mission that was nearly lost five years ago.

The original plan, on December 7, 2010, was for Akatsuki to burn its main engine and enter an elliptical orbit around Venus, from which it would study the planet’s atmosphere and surface. A blocked valve in the propulsion system caused it to miss the orbit insertion, and JAXA managers had to scramble to put together a plan for a second attempt in 2015 using smaller maneuvering thrusters instead of the main engine.  The new orbit is much higher—[Dec 9 update: the orbit is 400 kilometers by 440,000 km, with a 13-day period, as compared to the 30-hour, 300 x 80,000 km orbit that was originally planned]—and some of the science from the original plan will be compromised. Instrument degradation due to the extra five years in space is a possibility. Still, Japanese scientists hope for a full slate of observations using infrared and ultraviolet sensors, as well as a high-speed lightning detector.

If it works, Akatsuki could kick off a mini-surge in Venus observations over the next decade:

  • Two of the five contenders for a NASA Discovery mission launch in 2020 are Venus missions: the Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy mission (VERITAS), and the Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging (DAVINCI). The first would use synthetic aperture radar to map the planet’s cloud-covered surface from orbit, and the second would drop an instrumented probe down through the atmosphere to the surface, where it would return our first pictures of the broiling Venus landscape since the Soviet Venera probes of the 1980s.
  • Lucky for scientists interested in Venus, spacecraft bound for other places in the solar system often swing by the planet to get a gravity boost.  Three missions on deck—Europe’s 2017 Bepi-Columbo mission to Mercury and two solar probes planned for 2018—will offer opportunities for scientific observations during their respective Venus gravity assists.
  • In the more “iffy” category are concepts for a cubesat mission to study Venusian lightning and a lifting body called VAMP (Venus Atmospheric Manueverable Platorm) that could fly in the thick Venus atmosphere. The latter is just a concept—there are no current plans to fund such a thing—but a space fan can dream:
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