There’s still some time left before Europe’s Rosetta mission comes to an end in September, but it’s already time to say goodbye to the mission’s Philae lander — the first spacecraft ever to touch down on a comet. Tomorrow at 5AM ET, the European Space Agency will switch off the Electrical Support System Processor Unit (ESS) on the Rosetta spacecraft, which is currently orbiting around the comet that Philae landed on. The ESS is the system Rosetta uses to communicate with Philae, but researchers need to power it down to prepare for the end of the mission. Once it’s off, there will be no way for the two spacecraft to talk to each other.

Philae hasn’t been doing too much talking during its time on the comet

Though it’s a sad moment, Philae hasn’t been doing too much talking during its time on the comet. The last time researchers received data from Philae was back in summer of 2015, when Rosetta picked up a few sporadic signals from the lander. But Philae has remained silence ever since, despite numerous attempts to reestablish communication with the spacecraft over the past year. The ESS has been kept on during that time just in case the lander started talking again.

The communication issues likely stemmed from how Philae landed on the comet, called Comet 67P/Churyumov-Gerasimenko. When the lander first touched down in November, 2014, it was supposed to deploy harpoons to help anchor itself to the surface. But those harpoons didn’t fire, and Philae bounced a couple times before finally coming to rest in a shaded area. As a result, the lander didn’t get enough sunlight to power its solar panels, and it went into hibernation mode after two days.

A picture of the Philae lander, taken by Rosetta, as the spacecraft descended to the surface of Comet 67P. (ESA)

Researchers were initially hopeful that once Comet 67P got closer to the Sun, Philae would get enough sunlight to charge its solar panels again. And that seemed to be the case when the lander reactivated communication last summer. But when Philae went silent again, the Rosetta team suggested that extra heat from the Sun may have been to blame. The warmer temperatures may have caused the comet to emit gas, shifting the lander and the position of its antenna.

It’s guaranteed that Philae will no longer talk to Rosetta again

Now after a year of silence, it’s guaranteed that Philae will no longer talk to Rosetta again. The mission team is powering off the ESS in order to conserve Rosetta’s energy through the end of September. By the end of July, Comet 67P will be more than 320 million miles from the Sun, which means Rosetta won’t be getting as much power. The researchers are turning off all the "non-essential payload components" on Rosetta in order to maximize the amount of scientific operations the spacecraft can do over the next two months. Then on September 30th, Rosetta will make a controlled descent into Comet 67P, bringing its 12-year mission to an end.

But before Philae goes completely offline, the German Aerospace Center is asking social media users to help say goodbye. People are encouraged to send in pictures and personal messages to the lander, along with the hashtag #GoodbyePhilae. Here’s mine: