[27] The planning for the operation of the scientific payload, together with the data retrieval, calibration, archiving and distribution, was performed from the European Space Astronomy Centre (ESAC), in Villanueva de la Cañada, near Madrid, Spain.

[35][36][37] On 5 September 2016, ESA announced that the lander was discovered by the narrow-angle camera aboard Rosetta as the orbiter made a low, 2.7 km (1.7 mi) pass over the comet.

The lander sits on its side wedged into a dark crevice of the comet, explaining the lack of electrical power to establish proper communication with the orbiter.

[39] After the probes returned valuable scientific information, it became obvious that follow-ons were needed that would shed more light on cometary composition and answer new questions.

[71][72] In observations made on 7 and 8 November, Rosetta was briefly mistaken for a near-Earth asteroid about 20 m (66 ft) in diameter by an astronomer of the Catalina Sky Survey and was given the provisional designation 2007 VN84.

[74] However, astronomer Denis Denisenko recognised that the trajectory matched that of Rosetta, which the Minor Planet Center confirmed in an editorial release on 9 November.

[78] On 10 July 2010, Rosetta flew by 21 Lutetia, a large main-belt asteroid, at a minimum distance of 3,168±7.5 km (1,969±4.7 mi) at a velocity of 15 kilometres per second (9.3 mi/s).

While this may have caused the propellants to mix incompletely and burn 'dirtier' and less efficiently, ESA engineers were confident that the spacecraft would have sufficient fuel reserves to allow for the successful completion of the mission.

[80] Prior to Rosetta's deep space hibernation period, two of the spacecraft's four reaction wheels began exhibiting increased levels of "bearing friction noise".

After Rosetta exited hibernation in January 2014, lessons learned from the ground testing were applied to all four RWAs, such as increasing their operating temperatures and limiting their wheel speeds to below 1000 rpm.

[14][82] These changes allowed the four RWAs to operate throughout Rosetta's mission at 67P/Churyumov–Gerasimenko despite occasional anomalies in their friction plots and a heavy workload imposed by numerous orbital changes.

[81] In August 2014, Rosetta rendezvoused with the comet 67P/Churyumov–Gerasimenko (67P) and commenced a series of manoeuvres that took it on two successive triangular paths, averaging 100 and 50 kilometres (62 and 31 mi) from the nucleus, whose segments are hyperbolic escape trajectories alternating with thruster burns.

[90] Analysis of telemetry indicated that the surface at the initial touchdown site is relatively soft, covered with a layer of granular material about 0.82 feet (0.25 meters) deep,[91] and that the harpoons had not fired upon landing.

This made it unable to adequately collect solar power, and it lost contact with Rosetta when its batteries ran out after three days, well before much of the planned science objectives could be attempted.

[102] On 2 June 2015, NASA reported that the Alice spectrograph on Rosetta determined that electrons within 1 km (0.6 mi) above the comet nucleus — produced from photoionization of water molecules, and not direct photons from the Sun as thought earlier — are responsible for the degradation of water and carbon dioxide molecules released from the comet nucleus into its coma.

While it would have been possible to put Rosetta into a second hibernation phase during the comet's aphelion, there was no assurance that enough power would be available to run the spacecraft's heaters to keep it from freezing.

[108][109][111] The spacecraft's estimated speed at the time of impact was 3.2 km/h (2.0 mph; 89 cm/s),[19] and its touchdown location, named Sais by the operations team after the Rosetta Stone's original temple home, is believed to be only 40 m (130 ft) off-target.

[110][112] Rosetta's computer included commands to send it into safe mode upon detecting that it had hit the comet's surface, turning off its radio transmitter and rendering it inert in accordance with International Telecommunication Union rules.

[112][113] The investigation of the nucleus was done by three optical spectrometers, one microwave radio antenna and one radar: Previous observations have shown that comets contain complex organic compounds.

[133] Rosetta and Philae also searched for organic molecules, nucleic acids (the building blocks of DNA and RNA) and amino acids (the building blocks of proteins) by sampling and analysing the comet's nucleus and coma cloud of gas and dust,[133] helping assess the contribution comets made to the beginnings of life on Earth.

[134] Upon landing on the comet, Philae should have also tested some hypotheses as to why essential amino acids are almost all "left-handed", which refers to how the atoms arrange in orientation in relation to the carbon core of the molecule.

[135] Most asymmetrical molecules are oriented in approximately equal numbers of left- and right-handed configurations (chirality), and the primarily left-handed structure of essential amino acids used by living organisms is unique.

[137] The VIRTIS spectrometer on board the Rosetta spacecraft has provided evidence of nonvolatile organic macromolecular compounds everywhere on the surface of comet 67P with little to no water ice visible.

[142][143] Measurements by the COSAC and Ptolemy instruments on the Philae's lander revealed sixteen organic compounds, four of which were seen for the first time on a comet, including acetamide, acetone, methyl isocyanate and propionaldehyde.

[180] The script for each episode of the series is written by science communicators at the European Space Research and Technology Centre, who kept close with mission operators and the producers at Design & Data.

[180] To promote the spacecraft's arrival at comet 67P/Churyumov–Gerasimenko and the landing of Philae in 2014, a short film was produced by the European Space Agency with Polish visual effects production company Platige Image.

[185] British science fiction author and former ESA employee Alastair Reynolds spoke about the film's message at the premiere, stating to the audience that "our distant descendants may look back to Rosetta with the same sense of admiration that we reserve for, say, Columbus or Magellan.

Tim Reyes of Universe Today complimented the titular theme of ambition in the film, stating that it "shows us the forces at work in and around ESA", and that it "might accomplish more in 7 minutes than Gravity did in 90.

"[183] Ryan Wallace of The Science Times also gave praise to the film, writing, "whether you're a sci-fi fanatic, or simply an interested humble astronomer, the short clip will undoubtedly give you a new view of our solar system, and the research out there in space today.

A live stream of the control centres was set up, as were multiple official and unofficial events around the world to follow Philae's landing on 67P.