The European Space Agency’s Rosetta mission will deploy its lander, Philae, to the surface of comet 67P/Churyumov–Gerasimenko on Nov. 12.
Rosetta is an international mission spearheaded by the European Space Agency with support and instruments provided by NASA.
Philae’s landing site, currently known as Site J, is located on the smaller of the comet’s two “lobes,” with a backup site on the larger lobe. The sites were selected just six weeks after Rosetta’s Aug. 6 arrival at the comet, following the spacecraft’s 10-year journey through the solar system.
In that time, the Rosetta mission has been conducting an unprecedented scientific analysis of the comet, a remnant from early in the solar system’s 4.6-billion-year history. The latest results from Rosetta will be presented when Philae lands, during dedicated press briefings.
The main focus to date has been to survey 67P/Churyumov–Gerasimenko in order to prepare for the first-ever attempt to soft-land on a comet.
The descent to the comet is passive and it is only possible to predict that the landing point will be within a “landing ellipse” (typically a few hundred yards or meters in size). For each of Rosetta’s candidate sites, a larger area — four-tenths of a square mile (one square kilometer) — was assessed. Site J was chosen unanimously as the primary landing site because the majority of terrain within an area that size has slopes of less than 30 degrees relative to the local vertical and because there are relatively few large boulders. The area also receives sufficient daily illumination to recharge Philae and continue surface science operations beyond the initial 64-hour battery-powered phase.
Over the last two weeks, the flight dynamics and operations teams at ESA have been making a detailed analysis of flight trajectories and timings for Rosetta to deliver the lander at the earliest possible opportunity.
Two robust landing scenarios have been identified, one for the primary site and one for the backup. Both anticipate separation and landing on Nov. 12.
For the primary landing scenario, targeting Site J, Rosetta will release Philae at 08:35 UTC (12:35 a.m. PST; 9:35 a.m. Central European Time) at a distance of 14 miles (22.5 kilometers) from the center of the comet, landing about seven hours later. The one-way signal travel time between Rosetta and Earth on Nov. 12 will be 28 minutes and 20 seconds, meaning that confirmation of the landing will arrive at Earth ground stations at around 16:00 UTC (8 a.m. PST; 5 p.m. CET).
If a decision is made to use the backup site, Site C, separation will occur at 13:04 UTC (5:04 a.m. PST; 2:04 p.m. CET) at a distance of 7.8 miles (12.5 kilometers) from the center of the comet. Landing will occur about four hours later, with confirmation on Earth at around 17:30 UTC (9:30 a.m. PST; 6:30 p.m. CET). The timings are subject to uncertainties of several minutes.
Final confirmation of the primary landing site and its landing scenario will be made on October 14 after a formal Lander Operations Readiness Review, which will include the results of additional high-resolution analysis of the landing sites conducted in the meantime. Should the backup site be chosen at this stage, landing can still occur on Nov. 12.
A competition for the public to name the primary landing site will also be announced during the week of Oct. 14.
Following the Philae landing, the Rosetta orbiter will continue to study the comet and its environment using 11 science instruments for another year as the spacecraft and comet orbit the sun together. The comet is on an elliptical 6.5-year orbit that takes it from beyond Jupiter at its farthest point, to between the orbits of Mars and Earth at its closest to the sun. Rosetta will accompany the comet for more than a year as they swing around the sun and back to the outer solar system again.
The analyses made by the Rosetta orbiter will be complemented by the measurements performed on the comet by Philae’s 10 instruments.
Comets are time capsules containing primitive material left over from the epoch when the sun and its planets formed. By studying the gas, dust and structure of the nucleus and organic materials associated with the comet, the Rosetta mission should become key to unlocking the history and evolution of our solar system, as well as answering questions regarding the origin of Earth’s water and perhaps even life.