Japan’s Venus probe zeros in on Dec 7 arrival

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A Japanese Venus research spacecraft, dubbed Akatsuki, has completed all its preliminary course corrections and is ready for a December 7 orbital insertion attempt, the second since the spacecraft’s main engine failed during the first attempt in 2010.

The space probe accomplished its last targeting maneuver Oct. 11 to aim for its Dec. 7 arrival at Venus, and all systems are go for the encounter, said Takeshi Imamura, Akatsuki’s project scientist at JAXA’s Institute of Space and Astronautical Science. Imamura said the Akatsuki spacecraft, named for the Japanese word for dawn, will zoom 541 kilometers, or 336 miles, above Venus for a 20-minute insertion burn using the probe’s secondary attitude control thrusters. Japanese ground controllers have programmed the probe to use the backup rocket jets after a faulty valve knocked out Akatsuki’s main engine during its first attempt to enter orbit around Venus in December 2010.

Four of the eight attitude control thrusters aboard Akatsuki will fire for 20 minutes and 33 seconds to slow the spacecraft down enough for Venus’ gravity to pull it into an egg-shaped orbit that skims above the planet’s cloud tops on the low end and ranges several hundred thousand miles in altitude at peak altitude. The reaction control thrusters, originally designed to help point the spacecraft, were not rated for such a hefty propulsive maneuver.

To make this second chance possible, they have spent the last five years improvising. First they dumped the fuel from the now-useless main engine to make the spacecraft lighter so that the attitude control thrusters could handle the maneuvers. Then they used those thrusters repeatedly to adjust the course to bring Akatsuki back to Venus after it zipped past in 2010.

If they succeed in getting it in a useful orbit on December 7, it will be real triumph for these Japanese engineers.



  • Cotour

    An interesting date for the Japanese, was it by chance or chosen for symbolism? And if its for symbolism what would that be?

  • Nick P

    What is the mission of this spacecraft?

    Is there a lander?

  • The only reason it arrives on December 7 is because of orbital mechanics. You are being ridiculous to even think that they chose this date for other reasons, especially considering they have been struggling mightily just to save the mission with limited resources.

  • No. Landing on Venus is very very hard, and the Japanese never intended that. Akatsuki was originally intended to gather orbital data in concert with Europe’s Venus Express orbiter. Unfortunately, Venus Express’s mission ended in December 2014. The failure to gain orbit in 2010 means that Akatsuki’s data gathering, if it successfully makes orbit, will occur afterward instead.

  • Cotour


    There are 365 days in a year and the Japanese just happen to make an achievement in space exactly on that particular day, that’s at the minimum an interesting coincidence to me.

    It appears that there was no specific reason other than Dec 7th, 1941 was a Sunday and they believed that they would sink the most number of ships.

    And it was in fact on a Sunday: http://www.timeanddate.com/calendar/?year=1941&country=1

    Still interesting.

  • Yes, ridiculous. You think they can pick and choose the date Akatsuki is returning to Venus so easily? They are desperately improvising its return, using the tiny attitude thrusters meant only for adjusting its orientation and minor orbital corrections, not major mid-course corrections that shift its solar orbit from one planet to another.

    They don’t have the ability to pick any day. They are lucky they were able to get the spacecraft on a course that would return to Venus at all, no less in a way that might allow those tiny thrusters to put it into orbit.

    So, yes, I think it very ridiculous to suggest they picked the date so that it would commemorate their attack on Pearl Harbor in 1941

  • Cotour

    Even more interesting! Even if it is a coincidence.

    With all of the problems that they have been having and all of the technical improvs. they still arrive on Dec 7th.

    Any way you look at it coincidence is interesting, maybe why we exist in this universe in the first place?


  • Garry

    Having lived in Japan, I can tell you that most Japanese under, say, 70 years old don’t know a whole lot about Pearl Harbor, and I’ve never heard any Japanese person mention it. The attack is barely mentioned, if at all, in their history textbooks (the same ones are used nationwide, and are approved through a vigorous process). It’s not considered a big historical event in Japan at all; the Japanese had been at war for long before Pearl Harbor, and the few Japanese who ever said anything to me about the War (World War II vets) were always quick to blame the war on Churchill and/or Roosevelt. They would see Pearl Harbor as a natural response to the “aggression” by the west.

    As far as World War II events go, by far the biggest emphasis is on Hiroshima. Even mentioning Pearl Harbor would ruin that whole narrative.

    Besides, Pearl Harbor took place on December 8 Japan time; if any Japanese were to celebrate it, they would celebrate December 8 rather than December 7.

    And these factors may pale in comparison to what Bob mentioned about the constraints on timing.

    I suppose there’s a miniscule chance that some rogue official at NASDA (or whatever they call their equivalent of NASA these days) set this up to “celebrate” Pearl Harbor Day, but I would put it at much lower than 1/365.

  • chris l

    While I admit the timing is interesting, my guess is that the Japanese would have picked just about any other day of the year if they could have.

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