The countdown to the destruction of the European Space Agency’s Rosetta spacecraft has begun. The probe, which has been orbiting around a comet since the end of 2014, will make a controlled descent and crash into its rocky companion on September 30th. The spacecraft’s destruction will mark the end of the Rosetta mission, which has spanned the last 12 years.

The time is ripe for Rosetta to die

The time is ripe for Rosetta to die, according to ESA. The comet that it is orbiting — Comet 67P/Churyumov-Gerasimenko — is getting further and further away from the Sun as it heads out toward Jupiter. That means there will be way less solar power to keep the spacecraft working. And putting Rosetta into hibernation mode isn’t really an option. The spacecraft went into hibernation, or a low-power mode, in 2011 to help conserve energy before it reached Comet 67P. But this time Rosetta is orbiting the comet, and the comet’s path will take it way out into space — more than 525 million miles from the Sun. At that distance, mission scientists can’t guarantee Rosetta will get enough power to keep its heaters on. Plus, the spacecraft is getting pretty old, making it unlikely to survive such a lengthy trip.

It’s a bittersweet ending for the mission, which has experienced some high highs and low lows on its journey. Rosetta has made history multiple times over the past 12 years. In September 2014, it became the first spacecraft to orbit a comet. In November 2014, the mission made history yet again when Rosetta’s lander, called Philae, landed on Comet 67P, marking the first time a vehicle had touched down gently on a comet.

But as successful as Rosetta has been, the mission has also been plagued with problems. Philae may have successfully landed on Comet 67P, but it didn’t land as it was supposed to. During its descent, the lander failed to deploy its two harpoons, which were needed to help anchor Philae to the comet. As a result, the lander bounced twice and came to rest in one of the comet’s shaded regions. Philae was unable to get enough sunlight here to power its solar panels, so it shut down after two days when its batteries ran out. The lander was able to conduct some science when it first landed, but most of its main objectives were never completed.

As successful as Rosetta has been, the mission has also been plagued with problems

Numerous attempts were made to save the lost lander. Initially, scientists hoped that when the comet got closer to the Sun, Philae would get enough sunlight to power its batteries. And at first it seemed like that had worked. In June 2015, the lander started communicating sporadically with the Rosetta spacecraft again. But by July, Philae had stopped communicating again. It’s possible that the heated comet emitted gas that shifted the lander, causing its antenna to point in a different direction. Despite repeated attempts to establish communication, Philae has remained silent ever since.

Even though Philae didn’t collect as much data as expected, Rosetta’s crash landing offers hope of some last-minute science. First, the mission team will start maneuvering Rosetta into position in August. "Planning this phase is in fact far more complex than it was for Philae's landing," Sylvain Lodiot, ESA Rosetta spacecraft operations manager, said in a statement. "The last six weeks will be particularly challenging as we fly eccentric orbits around the comet — in many ways this will be even riskier than the final descent itself."

Then during descent, Rosetta will make as many observations as possible, such as taking high-resolution images of Comet 67P. That data will be transferred back to Earth and analyzed by the Rosetta team. "[September 30th] will mark the end of spacecraft operations, but the beginning of the phase where the full focus of the teams will be on science," Matt Taylor, ESA Rosetta project scientist, said in a statement. "That is what the Rosetta mission was launched for and we have years of work ahead of us, thoroughly analyzing its data."

How NASA pulled off the Pluto flyby