Fifteen years after launch, Japan has announced the end of the “Planet C” mission, leaving humanity with no presence around Venus.
In May 2010, Japan’s Aerospace Exploration Agency (JAXA) launched the “Planet C” spacecraft – also known as “Akatsuki” or the Venus Climate Orbiter – towards Earth’s “sister planet”. The early stages of the mission did not go as planned. On its approach to Venus in December 2010, the spacecraft was supposed to decelerate with a controlled burn to place it in orbit. But due to a malfunction with the main engine, the planned 12-minute burn lasted just three, and Planet C shot well past its target instead.
That could have been the end of it, but JAXA was able to use the spacecraft’s auxiliary reaction control system to adjust its trajectory and slow it down as it orbited the Sun. Five years later, the space agency announced that they had finally put the probe around Venus, and work could begin.
“As a result of measuring and calculating the Akatsuki’s orbit after its thrust ejection, the orbiter is now flying on the elliptical orbit at the periapsis altitude of about 400 kilometers and apoapsis altitude of about 440,000 kilometers from Venus,” the space agency announced in 2015. “The orbit period is 13 days and 14 hours. We also found that the orbiter is flying in the same direction as that of Venus’s rotation.”
Soon after that, the spacecraft began returning its first photographs and data, helping us to study the atmosphere of Venus. Though not in its original planned orbit, the orbit it ended up in was advantageous.
“Meteorological information is obtained by globally mapping clouds and minor constituents successively with four cameras at ultraviolet and infrared wavelengths, detecting lightning with a high-speed imager, and observing the vertical structure of the atmosphere with radio science techniques,” NASA explains.
“The equatorial elongated orbit with westward revolution matches the Venusian atmosphere, which rotates westward. The systematic, continuous imaging observations will provide us with an unprecedented large dataset of the Venusian atmospheric dynamics.”
The probe has had a few other minor issues in the intervening years, shutting down two of its five cameras in 2016 to keep it going. But spacecraft do not last forever, and in 2024, JAXA lost contact with Planet C. Over a year later, the team has finally called time on humanity’s only operational Venus probe.
“Communication with ‘Akatsuki’ was lost during operations near the end of April 2024, triggered by an incident in a control mode of lower-precision attitude maintenance for a prolonged period,” JAXA explained in a statement.
“Although recovery operations were conducted to restore communication, there has been no luck so far. Considering the fact that the spacecraft has aged, well exceeding its designed lifetime, and was already in the late-stage operation phase, it has been decided to terminate operations.”
Fifteen years after launch, JAXA has said goodbye to the spacecraft, well after its expected operational lifespan had ended.
“Akatsuki continuously observed Venus’s atmosphere for more than eight years,” JAXA continued. “The mission’s scientific achievements focused on planetary meteorology and included the discovery of the largest mountain wave (stationary gravity waves) in the Solar System, the elucidation of the mechanism that maintained high-speed atmospheric circulation (super-rotation) around Venus, and the application of data assimilation techniques (popular in Earth’s meteorological research) to Venus for the first time.”
While humans are temporarily out of Venus probes, there are plans to send more. NASA has long been planning to send three missions – DAVINCI, VERITAS, and the joint ESA mission EnVision – to the Morning Star in the late 2020s and early 2030s. However, all three missions are on the potential chopping block if Trump’s 2026 budget cuts make it through. Hopefully, they survive to one day tell us more about the planet and investigate the intriguing (but tentative) biosignatures seen on Venus in recent years.