Rosetta (spacecraft)

Rosetta was a European Space Agency probe launched on 2 March 2004. Together with its lander, Philae, it carried out an in-depth investigation of comet 67P/Churyumov–Gerasimenko. The spacecraft’s name came from the Rosetta Stone, an ancient Egyptian stele with a decree written in three scripts; the lander was named after the Philae obelisk, which has a bilingual Greek and hieroglyphic inscription. Comparing those hieroglyphs with the Rosetta Stone helped decipher Egyptian writing, and scientists hoped the spacecraft would similarly unlock secrets about comets and the early Solar System. Rosetta also carried a micro-etched nickel disc from the Long Now Foundation, inscribed with 6,500 pages of language translations.

The mission was the third cornerstone of ESA’s Horizon 2000 programme, following SOHO/Cluster and XMM-Newton. Total cost was about €1.3 billion (US$1.8 billion). The orbiter carried 12 instruments, and the Philae lander had nine more. Rosetta launched from the Guiana Space Centre on an Ariane 5 rocket. During its journey, it performed flybys of Earth, Mars, and the asteroids 21 Lutetia and 2867 Šteins. It reached comet 67P in May 2014, then executed manoeuvres to enter orbit on 6 August 2014, becoming the first spacecraft ever to orbit a comet nucleus. On 12 November 2014, Philae made the first successful soft landing on a comet, though its battery died two days later. Brief contact with Philae was restored in June and July 2015, but Rosetta’s communications module for the lander was switched off on 27 July 2016. The mission ended on 30 September 2016 when Rosetta hard-landed on the comet’s Ma’at region.

Rosetta achieved many historic firsts. It was the first European probe to closely encounter primitive objects in the main asteroid belt, and the first spacecraft to fly near Jupiter’s orbit using solar cells as its main power source. It was the first to orbit a comet nucleus and to fly alongside a comet as it moved toward the inner Solar System. Previous missions had only performed flybys of seven other comets. Rosetta was the first to examine up close the activity of a frozen comet as it warmed by the Sun. Philae’s instruments obtained the first images from a comet’s surface and made the first on-site analysis of its composition.