Today is a historical day! Earlier, the Rosetta spacecraft reached Comet 67p/ Churyumov-Gerasimenko, after a ten-year journey. It’s currently in orbit around the comet at a distance of about 100 km (62 miles). As you read this, both the comet and the spacecraft are flying at a speed of 55 000 km/h (34,000 mi/hr) and are currently about 400-million km (250-million miles) from Earth. Rosetta has already been able to help scientists study the comet and (of course) it’s taken several fantastic images of its body.
As the Rosetta spacecraft reached the comet, cheers broke at the ESA’s headquarters in Darmstadt, Germany: “After ten years, five months and four days traveling towards our destination, looping around the Sun five times and clocking up 6.4 billion kilometres, we are delighted to announce finally ‘we are here’,” says Jean-Jacques Dordain, ESA’s General Director.
The 1.7 billion dollar (1.3 billion euro) project was at first designed to land on Comet 46P/Wirtanen, but as the mission was delayed, the Comet 67P/Churyumov-Gerasimenko became the new choice. Still, the mission was not an easy success. Since May 2014, the Rosetta’s speed and trajectory were gradually adjusted through a series of complex maneuvers. If one of those calculations had been wrong, Rosetta would have simply flown past its destination.
“Today’s achievement is a result of a huge international endeavour spanning several decades,” says Alvaro Giménez, ESA’s Director of Science and Robotic Exploration.
Early images of the comet taken in April by the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) showed the comet’s variable activity. The comet’s tail started to brighten very rapidly and then dimmed again, all within one week. With the help of other instruments, the ESA was able to collect a lot of fascinating information, such as seeing how much water the comet emits (which is about 30 mL/sec). The imaging spectrometer on the spacecraft revealed the comet’s average temperature to be about 70° C (158° F), which suggests that the surface is mostly dark and dusty.
Images taken at a distance of 12,000 km from the comet revealed another fascinating fact: The comet is actually made of three parts, a head, a neck and a body, which makes it look like rubber-duck.
“Our first clear views of the comet have given us plenty to think about,” says Matt Taylor, ESA’s Rosetta project scientist.
Now, Rosetta is orbiting at about 100 km from the comet’s surface. The truly interesting part is only beginning. During the upcoming weeks, the spacecraft will gradually edge closer to the comet by completing a series of triangular maneuvers as seen in the video above. The distance between the comet and the spacecraft will diminish to about 30 km. The pictures and measurements taken during this decent are very important and will help the ESA determine a safe landing site for Rosetta’s lander, Philae.
“Arriving at the comet is really only just the beginning of an even bigger adventure, with greater challenges still to come as we learn how to operate in this unchartered environment, start to orbit and, eventually, land,” says Sylvain Lodiot, ESA’s Rosetta spacecraft operations manager.
When a landing site will be chosen, around mid-September, and confirmed, the Philae lander will be launched and will land on the surface of the comet.
The Rosetta spacecraft is named after the Rosetta stone which helped decipher Egyptian hieroglyphs. The Philae lander, named after an obelisk found in the Nile River, will land (yes, actually LAND) on the comet to collect samples and learn more about the comet’s composition. The Rosetta Mission is, just like the Egyptian tablet, we hope, will help scientists decipher some of the mysteries surrounding comets and it’ll (hopefully) help us get a better understanding of our own Solar System and its early history.