It was decades in the making and was one of those super expensive missions that people said may fail outright. Rosetta was supposed to throw itself at comet 67P/Churyumov-Gerasimenko and drop a little lander on the surface.
It was then to study as much about the dirty snowball as it could then send all the science data, and thousands of high-resolution photos, back to mission control at the European Space Agency.
Sounds simple enough, doesn't it? Well, actually it wasn't. Getting up to speed with gravity assists from the inner planets was hard enough, then adjusting it's course to rendezvous with an object millions of miles away from Earth, itself travelling at huge speeds ... well, you can imagine how difficult that was.
The scientists put Rosetta to sleep for part of the journey and were really nervous about it waking up when it got close enough to comet 67P to start making course adjustments to put it into the orbit of the comet.
There was no guarantee that it would wake up after travelling in the cold of space for so long. Thankfully it did, or the mission would have immediately failed.
An excellent little sci-fi movie explaining Rosetta
And what a mission it was! I watched the release of the little Philae lander live, and when it gave them the signal that it had landed, I was jumping for joy along with the scientists in mission control. We'd done us! We'd landed on a comet!
Sadly, Philae bounced a couple of times and ended up on its side in the shadows at the foot of a cliff, but it still managed to send back some valuable science before its batteries ran out around 60 hours later.
Here are 8 things Rosetta and Philae did:
Orbiting a comet for the first time
Landing on a comet for the first time
Sniffing a comet and relaying its smell back to Earth
Detecting some of life’s ingredients in a comet
Watching a comet change during its closest approach to the sun
Stoking debate about the origins of water on Earth
Revealing why comet 67P is shaped like a rubber ducky
Finding common ground between comets and Florida sinkholes
After 2 years in orbit of 67P, and with some seriously close approaches producing a multitude of amazing images, the scientists at mission control had to make a decision about what to do with Rosetta.
Should they shut it down and leave it in orbit of the comet, with the hope of waking it again in a few years? Or should they crash it into the comet and let it rest along with its little brother Philae?
They chose to crash land on the comet. Manoeuvring fuel was running low and with solar power dropping off as the comet moved away from the sun, it was decided to crash land Rosetta on the surface of 67P.
It was a gentle crash because of the comet's gravity, so slow that it could have survived reasonably intact. The mission team programmed the onboard computer to completely shut down when it felt a jolt.
67P/Churyumov-Gerasimenko has been travelling around the sun for over 4 billion years, and now it has two passengers to continue its journey with, Rosetta and Philae.
How long the comet lasts before breaking up close to the Sun we don't know, but potentially they could all be travelling together for millions of years.
So long and thanks for all the science. You totally inspired me, but more importantly, you'll have inspired young people who are, hopefully, now more interested in space and science and will be part of future space missions, helping us to understand the Universe and our own place in it.
Goodbye Rosetta and Philae!
To the entire Rosetta mission team, from the scientists, the engineers and the mission controllers to the European Space Agency who funded it, I say thank you.
Rosetta was an utterly audacious mission and to get a 99% success rate (I took one percentage point away because Philae fell over) was fantastic. Well done!