Help Shape the Future of Space Exploration

Join The Planetary Society Now  arrow.png

Join our eNewsletter for updates & action alerts

    Please leave this field empty

Headshot of Emily Lakdawalla

Timeline for Akatsuki's second attempt at orbit insertion

Posted by Emily Lakdawalla

04-12-2015 18:31 CST

Topics: mission status, Akatsuki (Planet-C)

This is it: Akatsuki's final chance at Venus orbit insertion. The rocket firing should begin on December 7 at 08:51 Japan time (December 6 23:51 UT / 15:51 PST) and last for 20 minutes. If for some reason the first rocket firing doesn't work, they'll turn the spacecraft about and try again with the opposite set of thrusters. We'll know right away if the rocket firing was successful, but it will take a couple of days of radio tracking to be sure that Akatsuki's modified path is one that will remain in a closed loop around Venus.

I don't currently know of any online webcast related to this arrival attempt -- I will update this post if I have any recommended places to view the event other than Akatsuki's official Twitter account. Just a few minutes ago, they posted an update that they are now only 430,000 kilometers from Venus -- similar to the Earth-Moon distance. So close...

Akatsuki attempting orbit insertion

Go Miyazaki

Akatsuki attempting orbit insertion

You can read Ralph Lorenz' excellent story for the details on how we got here. A Japanese fan website has posted an incredibly detailed slide presentation on the upcoming orbit insertion and science plans, in Japanese of course. I found a diagram describing the orbit insertion and a timeline and ran text through Google Translate and read some tweets by a helpful space fan and can provide the following, hopefully correct, information.

  • Sunday, December 6 (Japan time): Akatsuki turns to orbit insertion attitude.
  • Dec 7 04:30 JST / Dec 6 19:30 UT / Dec 6 11:30 PST: Usuda Deep Space Center begins tracking Akatsuki.
  • Dec 7 08:22 JST / Dec 6 23:22 UT / Dec 6 15:22 PST: Akatsuki enters Venus' penumbra.
  • Dec 7 08:51 JST / Dec 6 23:51 UT / Dec 6 15:51 PST: Akatsuki fires one set of RCS thrusters for about 20 minutes to enter Venus orbit.
  • After the firing, Akatsuki will automatically rotate to prepare for a second attempt at orbit insertion with its opposite set of RCS thrusters. Akatsuki will wait for instruction from Earth to find out if the second attempt is needed.
  • Dec 7 12:00 JST / Dec 7 03:00 UT / Dec 6 19:00 PST: JAXA will hold a press briefing from Sagamihara. At the press briefing, they will only be able to say whether or not the attitude control system functioned as commanded. It will take until December 9 to confirm that the spacecraft successfully entered Venus orbit. Another press briefing is scheduled for that day.
  • December 7, afternoon (Japan time): Canberra Deep Space Network begins tracking Akatsuki.

Here's the translated diagram -- you can see how small a change in trajectory the orbit insertion makes, at least initially:

Akatsuki orbit insertion trajectory

JAXA / translated by Emily Lakdawalla

Akatsuki orbit insertion trajectory

 Everybody cross your fingers for a successful arrival for Akatsuki at Venus!

See other posts from December 2015


Or read more blog entries about: mission status, Akatsuki (Planet-C)


Mewo: 12/05/2015 02:56 CST

So Akatsuki will get at least one close pass of Venus even if the thruster firing does not go as planned. That's *some* science at least. Obviously I hope it goes flawlessly. Good luck JAXA!

Karen: 12/05/2015 08:15 CST

Question, in case anyone knows: why don't they ever set up the RCS thrusters to be able to function as resistojets? I can't imagine that the mass penalty is significant - electric heaters are very light - and it gives them a way to get high ISP out of simple monoprop thrusters (albeit at the cost of orders of magnitude lower average thrust due to the charging time requirements)

masanori: 12/05/2015 10:43 CST

Thank you very much Emily for telling the world about this mission. In case there's someone misunderstanding it, the PDF linked from this blog post is a official document from the project which was used on the press conference on 9th Nov 2015. Not made by a fan. I think the timeline reported here is correct. But in case there's someone misunderstanding about the rotation after the firing of the thrusters: Akatsuki will rotate (pre-programmed) to prepare to fire its opposite set of RCS thrusters, for a case the project sees the need of additional firing, after the firing which starts at 8:51 JST. So if they sees no need to, they will not fire anything after the rotation. If they sees the need, they will fire the additional firing "live". The press conference on 9th Nov 2015 can be seen at In case you would like to send a message to the project team directly, post it at Along with its science/engineering, I really wish the world know the Akatsuki project team is a good model of attitude/behaviour a team which runs such mission should be like. I mean, they are concentrating on reality, when facing the public. They have not tried to confuse/brainwash public by giving things which make the team & the mission look better than they are. With reportedly a rather small budget, they also have kept updating the status of the mission to public all through the past 5 years (Akatsuki-kun, or the project's Twitter account, has been contributing so hugely). They had held self-origanised public talk events regularly with the help of Sagamihara City Museum which is located at just the other side of the street from ISAS. I think I have seen & chatted with the team members for 2 dozens or maybe more occasions, face to face, and I have seen that such attitude/behaviour is in everyone in the team. I have seen it

masanori: 12/05/2015 10:48 CST

(continued, if I typed more than the maximum number.) I have seen it even in Akatsuki-kun, too. In fact this is not an attitude/behaviour you usually see in JAXA today. But one of the very good sides of Japanese tradition. Perhaps that's why I believe Akatsuki deserved the right to be the first Japanese spacecraft to succeed to enter off-Earth planet's orbit. Akatsuki should be the one.

Lucas: 12/06/2015 08:02 CST

Excellent comment from masanori, totally agree with the great team attitude. Go Akatsuki!

Leave a Comment:

You must be logged in to submit a comment. Log in now.
Facebook Twitter Email RSS AddThis

Blog Search

Planetary Defense

An asteroid or comet headed for Earth is the only large-scale natural disaster we can prevent. Working together to fund our Shoemaker NEO Grants for astronomers, we can help save the world.


Featured Images

Jupiter from Juno at Perijove #4
Jupiter in approximate true color during Juno perijove 4
More Images

Featured Video

Class 9: Saturn, Uranus, and Neptune

Watch Now

Space in Images

Pretty pictures and
awe-inspiring science.

See More

Join The Planetary Society

Let’s explore the cosmos together!

Become a Member

Connect With Us

Facebook, Twitter, YouTube and more…
Continue the conversation with our online community!