Rosetta’s 7-billion-kilometer space mission

PARIS - European spacecraft Rosetta will end its mission on September 30 after traveling almost seven billion kilometers (4.4 billion miles) to probe the secrets of comets, with help from a high-tech robot named Philae.

The €1.4-billion ($1.6-billion) project has spanned 23 years and involved 14 European countries, as well as the United States.

A chronology:

Blastoff

Rosetta and Philae blasted off from the Kourou launch center in March 2004, the culmination of a ten-year development program by the European Space Agency (ESA).

The goal of the mission was nothing less than probing the origins of life by analysing dust from a comet called 67P/Churyumov-Gerasimenko, a time capsule from the birth of our solar system.

In the comet's orbit for more than two years, Rosetta sniffed, tasted and photographed the comet from all angles.

And it released Philae, the size and shape of a washing machine, onto the surface to analyse elements and send data to Rosetta for relay back to Earth.

Rosetta used the gravity of Earth and Mars to slingshot four times—in a game of cosmic billiards—towards the Sun.

On its ten-year journey to the comet, the probe passed Earth three times (2005, 2007 and 2009), and flew by Mars once in 2007.

Nap time

After more than seven years of travel, Rosetta found itself some 800 million kilometers (500 million miles) from the Sun, its rechargeable batteries fading.

The spacecraft went into "hibernation" to conserve energy in June 2011, when it was about one billion kilometers (620 million miles) from Earth.

After 957 days in this artificial coma, Rosetta was woken up in January 2014 for its rendezvous with "67P."

It entered the comet's orbit in August that year after a six-billion-kilometer (3.7-billion-mile), decade-long trek.

Hard landing

On November 12, 2014, Philae made a historic landing on the comet. But its harpoons failed to fire, causing it to bounce several times and end up in a ditch, hidden from the Sun's battery-replenishing rays. Ground control could not pinpoint its exact location.

But Philae's 10 instruments managed to work for around 60 hours, providing scientists with unprecedented data before entering standby mode.

In June 2015, the robot-lab surprised ground control crews with an unexpected message: "Hello Earth! Can you hear me?"

Last contact was on July 9, 2015.

Front-row seat

In August 2015, the comet came within 186 million kilometers (115 million miles) of the Sun, its closest point. Rosetta had a front-row seat for the spectacular plumes of gas and dust that comets typically generate when they get close to white-hot stars.

Philae refound

On September 2, 2016, Rosetta was about a month from the scheduled end of its mission when a camera spotted Philae—still on the comet—"at the foot of a cliff in an extremely rocky zone," in the words of project chief Philippe Gaudon.

After bouncing, the photo showed, the probe had came to a stop "with one foot in the air" and its antennae pointing into the ground.

The ESA decided to let Rosetta crash-land nearby on September 30, reuniting the intrepid duo forever in a fitting end to their historic mission.

— Agence France-Presse