Tonight is the Last Chance for Japan's Venus Orbiter to Reach the Planet

We may earn a commission from links on this page.

Japan’s Akatsuki spacecraft is desperately trying to claw its way into Venus orbit tonight. After blowing its orbital insertion five years ago, this is an incredible second chance for the spacecraft brought about by impressive ingenuity from the engineering team.

Artist’s concept of Akatsuki observing the clouds of Venus. Image credit: JAXA

Akatsuki originally attempted to slip into orbit around Venus in December 2010. During the extended main engine burn intended to alter its trajectory to orbit the planet, the spacecraft’s fuel valve choked leading to a jump in engine temperature. Although it’s hard to tell from hundreds of millions of kilometers away, it looks like this temperature spike led to structural failures. Just under 3 minutes into the 12-minute burn, the spacecraft started spinning as though the ceramic nozzle directing thrust had fallen apart. The fault-detection system shut down the burn before things got even worse, but the spacecraft missed its window and soared helplessly past Venus out into space.


Venus in ultraviolet taken after the failed orbital insertion in 2010, confirming that Akatsuki’s cameras were still functional. Image credit: JAXA


Akatsuki’s engineers were faced with a functioning spacecraft loaded with gorgeous cameras to track weather, but no planet to observe. Heartbroken but undaunted, they sat down to plan out a daring alternative. Their spacecraft would pass near Venus again one day (today!) and even though the main engine was blown they still had functioning maneuvering thrusters.

It wouldn’t be easy: they had to keep Akatsuki functioning far past its two-year intended lifespan, and it would mean going far closer to the Sun than ever intended. They’d need to get lucky to not be fried by skimming too close, and not get hit by a stray solar storm. But they did get lucky, and tonight is their second chance.


It hasn’t been easy for Akatsuki to stay cool while catching back up with Venus. Image credit: JAXA


Last night, Akatsuki rotated into the correct attitude for orbital insertion. By now, it’s closer to the planet than the Moon is to the Earth. At 23:51 UT (6:51pm ET), the spacecraft will start firing a set of four Reaction Control System thrusters. The burn will last 20 minutes, far beyond design capacity and longer than they’ve ever burned before. This should slip Akatsuki into orbit around Venus—a large, looping orbit at higher altitude than the original mission design, but orbit.

But just in case disaster strikes again, the mission control team have one last trick up their sleeves. At the end of the first burn, the spacecraft will automatically flip around ready to try again with its second set of opposing maneuvering jets.


Simulation of Akatsuki’s second attempt at flinging itself into orbit. Image credit: Isana Kashiwai/Go Miyazaki


If it succeeds, Akatsuki will be the first spacecraft to study Venus since the European Space Agency’s Venus Express hit end-of-life and crashed into the atmosphere last year. The spacecraft is equipped with five cameras to study Venus’s complex weather patterns.

We don’t know of any official live stream to watch along with this outrageous plan. Reader Tanarin points at this Japanese-language stream, while the Planetary Society is hosting this English-language reports from Venus researcher Sanjay Limaye from the control room in Sagamihara.

We won’t even know if it works right away. The Japanese space agency (JAXA) will hold a press conference at noon local time (December 6 10pm ET) to tell us if the jets even fired, but it will take until December 9th (and a second press conference) to know if the maneuvers worked.


You can follow updates from the Akatsuki team on Twitter at @Akatsuki_JAXA. The spacecraft is being tracked by the Deep Space Network as PLC (Planet-C), which you can watch live on the NASA Eyes website. While we have no livestream from mission control, you can watch a real-time simulation of what is ideally happening with Akatsuki here. If you need to keep your fingers busy during the critical moments, you can make a paper scale model of the spacecraft using this pattern.


Akatsuki and Venus together again! Image credit: NVS

UPDATE: Based on the happy expressions, “Yatta!” and celebratory handshakes, it appears the burn went according to plan. But is it enough? The change in velocity (delta-v) needs to be more than 152 metres per second, or else Akatsuki will fling it right back out of Venus orbit again.


During tonight’s press conference, project manager Masato Nakamura reports:

“We have to wait another two days to confirm the orbit. I am very optimistic. It is important to believe in success!”


We also heard that at one point, Akatsuki produced greater than 100% of the theoretical thrust, so performed even better than expected. We’ll be back on Wednesday with confirmation on if the spacecraft now circles Venus, or if it’s still trapped by the Sun’s massive gravitational pull.

Update: Orbit confirmed!!!

[JAXA | Planetary Society | Planetary Society | JAXA]

Top image: Don’t worry Venus, Akatsuki will be back! Credit: JAXA

Contact the author at or follow her at @MikaMcKinnon.