Rosetta's lander Philae is warming up to land on comet 67P/Churyumov-Gerasimenko in just a few hours. It will be our first-ever attempt at touching down on a dirty chunk of ice in space. But how close have we gotten to a comet before?
Up close and personal with the surface of comet 67P/Churyumov-Gerasimenko from just 10 kilometers away. Image credit: ESA
The Open University developed an instrument on the lander, Ptolemy, a miniature chemical analysis suite. In their anticipation of the upcoming landing, they put together a timeline of past missions, tracking how we've gotten closer and closer to finally touching landing gently on a comet.
1985: NASA's International Cometary Explorer came within 7,800 kilometers of comet Giacobini-Zinner's nucleus.
If the International Cometary Explorer (ICE) sounds vaguely familiar, that's because that was the new name of 1970s ISEE-3 satellite that was crowdfunded, recovered after a global distributed effort, and is now doing citizen science again.
Comet Giacobini-Zinner. Image credit: NASA/JPL
1986: The international Halley Armada converged on Halley's Comet, with satellites getting to within 600 meters of the nucleus.
Halley's Comet from just 600 meters away. Image credit: ESA
Russia's Vega 1 was the first to arrive, coming within 8,889 kilometers; Japanese Aerospace Exploration Agency's Suisei came within 151,000 kilometers. Both satellites had long-distance twins: Vega 2 kept farther away at 14 million kilometers and Sagigake kept to a slightly more daring 6.9 million kilometers. NASA's ISEE-3/ICE joined the party, farthest out at 40.2 million kilometers off the sunward side to collect solar wind data. The European Space Agency sent just a single satellite, but Giotto was the most adventurous, darting to a mere 600 meters of the comet.
2001: NASA's Deep Space 1 came within 2,200 kilometers of Comet Borrelly.
Comet Borrelly from within 2,200 kilometers. Image credit: NASA
Technology demonstration mission Deep Space 1 sidled up to Comet Borrelly after visiting 9969 Braille. The satellite came within 2,200 kilometers to take photographs and infrared spectra of the nucleus.
2002: NASA's Comet Nucleus Tour fails in its mission to do sub-100 kilometer flybys of comets Encke and Schwassmann-Wachmann-3.
The Comet Nucleus Tour (Contour) launched successfully, but NASA lost contact with the satellite after a planned manoeuvre intended to send the spacecraft out of Earth orbit. Ground-based observations suggest Contour broke into pieces.
2004: NASA's Stardust swooped within 240 kilometers of comet Wild 2, and completed the first sample-return from a comet.
The nucleus of Comet Wild 2 seen from within 240 kilometers. Image credit: NASA
2005: NASA's Deep Impact directly impacts comet Tempel 1.
Tempel 1 from 500 kilometers. Image credit: NASA
Deep Impact did exactly as its name suggested: while the main satellite stayed at a safe 500 kilometers from the comet, it ejected an impactor to hit the comet to investigate the comet's inner composition. Stardust managed to visit a few years later in 2011, coming within 178 kilometers of the comet and spotting 300-meter diameter craters hit by Deep Impact's impactor.
2010: NASA's EPOXI flies within 694 kilometers of Comet Hartley 2.
Comet Hartley 2 from just under 700 kilometers distance. Image credit: NASA/JPL-Caltech/UMD
After completing its primary mission, Deep Impact was renamed to EPOXI and sent chasing an extremely active comet, Hartley 2. This was the satellite's final mission, as it experienced a failure that prevented it from phoning home in 2013.
2014: ESA's Rosetta slips into orbit just 10 kilometers out from Comet 67P/Churyumov–Gerasimenko.
Landing site Agilkia on the surface of Comet 67P/Churyumov–Gerasimenko from 10 kilometers away. Image credit: ESA
Rosetta slipped into orbit around fChuryumov–Gerasimenko earlier this year. After mapping the comet's surface, landing site Agilkia was selected as the target for its lander Philae. If everything goes well, tomorrow will be an all-new first for our exploration of comets as Philae gently touches down and screws itself on to the surface of the comet.
Good luck, Philae. We'll all be cheering for you! You can watch the landing live on the European Space Agency's website.