DETROIT – The Rosetta spacecraft – which has been moving along in tandem with Comet 67P since August, 2014 – completed its mission today.
And though it was a crazy ending, I’ll tell you about that in a moment.
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It’s sad to see this wonderful mission end. Who can forget the excitement two years ago, when Rosetta arrived at its comet? But now, the comet and spacecraft are getting farther and farther from the sun. The craft is heading out towards the orbit of Jupiter and, consequently, it’s receiving less sunlight. The solar power needed to operate the craft and its instruments is waning, and there’s been a reduction in the bandwidth available to downlink scientific data back to the European Space Agency (ESA), which spearheaded the mission.
Plus, Rosetta and her instruments are aging. The mission launched on March 2, 2004, aboard an Ariane 5 rocket. On its way toward a rendezvous with its comet, Rosetta made four slingshot flybys to boost its speed via gravitational assist — one around Mars and three around Earth. Now, Rosetta has been in the harsh environment of space for over 12 years, the last two of which were in the dusty environment of Comet 67P in the most volatile part of its orbit, as it swung in near the sun before and after its perihelion (closest approach) on August 13, 2015.
Rosetta is now about 356 million miles from the sun and 447 million miles from Earth. The one-way communication signal travel time from the spacecraft to Earth is now about forty minutes. In addition, if the mission were to continue, Rosetta’s operators would be facing reduced communications due to a conjunction of the comet and spacecraft (that means they will be edging into the sun’s glare). ESA says that this is another contributing factor to concluding the mission now.
But what a mission it has been. On Aug. 6, 2014, Rosetta became the first mission in history to rendezvous with a comet and escort it as it orbits the sun. About two months later, the small lander, named Philae, deployed from Rosetta, touched down on the comet and bounced several times before aligning on the surface. Philae obtained the first images ever taken from the surface of a comet, and sent back valuable scientific data for several days.
Philae’s whereabouts on the comet became quite a mystery, and all hope of finding the exact point where it landed was almost gone when, just three weeks ago, Rosetta snapped a photo that allowed a sharp-eyed scientist to find it!
Photo: Rosetta's imager found the Philae lander less than one month before the mission ends.
So how did scientists end this mission? With a controlled, slow descent to the comet’s surface! The final hours of descent enabled Rosetta to make many once-in-a-lifetime measurements, including very high-resolution imaging, boosting Rosetta’s science return with precious close-up data achievable only through such a unique conclusion. Communications ceased, however, once the orbiter reached the surface, and its operations ended.
"We’re trying to squeeze as many observations in as possible before we run out of solar power," says Matt Taylor, ESA Rosetta project scientist. "September 30 will mark the end of spacecraft operations, but the beginning of the phase where the full focus of the teams will be on science. That is what the Rosetta mission was launched for, and we have years of work ahead of us, thoroughly analyzing its data.”
Here is Rosetta's last image, taken only 167 feet before it hit the comet's surface:
On a personal note, if you watched my coverage of this mission on Local 4, you saw an extra level of excitement as I shared developments with you. That’s because I consider Rosetta to be one of the most important space research missions ever. Why? Because comets are time capsules containing primitive material left over from when our sun and its planets formed. Rosetta is the first spacecraft to witness up close how a comet changes as it is subjected to the increasing intensity of the sun's radiation. Observations will help scientists learn more about the origin and evolution of our solar system and the role comets may have played in the formation of planets. By learning about comets, we learn about ourselves, and how Earth developed.
Farewell, Rosetta, and kudos for a job well done.
This image (below) from Rosetta was taken during its controlled descent to Comet 67P at an altitude of only ten miles. It’s one of the best images ever of the surface of a comet!
