The stage is set for the most dramatic scene yet in the epic voyage of Europe's space probe Rosetta, whose payload, Philae, will make the first landing on a comet next Wednesday:
The historic attempt to land on a comet will take place more than 500 million kilometres (310 million miles) from Earth.
Approved in 1993, the production cost about 1.3 billion euro ($1.61 billion), involving around 200 backstage staff and 50 companies from 14 European countries and the United States.
ROSETTA, a three-tonne aluminium box of 2.8 x 2.1 x 2.0 metres (9.2 x 6.9 x 6.5 feet) with two 14m solar arrays.
The orbiter carries 11 instruments to map the comet's surface and analyse its atmosphere, gases in its tail, the dust it emits and its subsurface temperature, mass, density and gravity.
Rosetta got its name from the stone that led to the deciphering in the 19th century of Egyptian hieroglyphics.
PHILAE, a 100-kg (220-pound) lab named after an obelisk on the Nile whose inscriptions were a key to the Rosetta stone.
It carries 10 instruments, including X-ray detectors to scan the comet's composition, micro-cameras for panoramic shots and radiowave probes of the comet's internal structure.
Philae has a drill to take subsurface comet samples from a depth of about 20 centimetres (eight inches) for onboard chemical analysis.
It will relay the results of its experiments to Rosetta, to be passed to Earth.
Its battery is charged to give it around 60 hours' operating time, but the probe could continue its work until March if the sunlight and temperature are right for its solar panels.
67P/CHURYUMOV-GERASIMENKO, a pitch-black 4-km comet named after two Ukrainian astronomers who first spotted it in 1969.
The first part of its moniker refers to the fact that it was the 67th "periodic comet" discovered - these orbit the Sun in less than 200 years.
The comet comprises two lobes joined by a narrow "neck", giving it the silhouette of a toy bath duck.
If it could be brought back to Earth, it would smell like a bad mix of rotten eggs and horse urine, among other things, tests of its escaping gases suggest.
The prime landing site, dubbed Agilkia after an island on the Nile, is on the smaller lobe roughly where the duck's forehead would be.
Launched on March 2, 2004, Rosetta was placed in a two-and-a-half-year hibernation in June 2011 to limit power and fuel consumption on its six-billion-kilometre (3.7-billion-mile) journey.
Because there was no rocket powerful enough to place it directly into orbit, the craft was designed to be catapulted around the Solar System with gravity boosts from Mars and Earth on four flybys between 2005 and 2009.
Awoken from slumber in January this year, Rosetta arrived at the comet on August 6.
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Once Rosetta is aligned correctly, Philae is meant to self-eject at 0835 GMT from a distance of some 20 km and unfold its three legs for what will hopefully be a gentle touchdown.
The self-adjusting landing gear is meant to ensure Philae stays upright, even if it lands on a slope. It will avoid escaping the comet's weak gravity by shooting two harpoons into its surface and using screws in its feet to secure itself to the surface.
If all goes well, signals giving confirmation of the landing will arrive on Earth at 1602 GMT.