After a decade-long journey chasing its target, the European Space Agency's Rosetta, carrying three NASA instruments, became the first spacecraft to rendezvous with a comet. The last of a series of 10 rendezvous maneuvers that began in May, to adjust Rosetta's speed and trajectory to gradually match those of comet 67P/Churyumov-Gerasimenko, occurred today (Aug. 6, 2014).
Comet 67P/Churyumov-Gerasimenko and Rosetta are 252 million miles (405 million kilometers) from Earth, about halfway between the orbits of Jupiter and Mars. The comet is in 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 over a year as it swings around the sun and back out towards Jupiter again.
Rosetta is 62 miles (100 kilometers) from the comet's surface. Over the next six weeks, it will fly two triangular-shaped trajectories in front of the comet, first at the 62-mile (100-kilometer) altitude and then down at 31 miles (50 kilometers). At the same time, the spacecraft's suite of instruments will provide a detailed scientific study of the comet, scanning the surface to identify a target site for its comet lander, Philae. Eventually, Rosetta will attempt a close, near-circular orbit at 19 miles (30 kilometers) and, depending on the activity of the comet, may come even closer.
"Over the next few months, in addition to characterizing the comet nucleus and setting the bar for the rest of the mission, we will begin final preparations for another space history first: landing on a comet," said Matt Taylor, Rosetta's project scientist from the European Space Agency's Science and Technology Centre in Noordwijk, The Netherlands.
As many as five possible landing sites will be identified by late August, before the primary site is identified in mid-September. The final timeline for the sequence of events for deploying Philae -- currently expected for Nov. 11 -- will be confirmed by the middle of October.
Comets are considered to be primitive building blocks of the solar system and may have helped to "seed" Earth with water, perhaps even the ingredients for life. But many fundamental questions about these enigmatic objects remain, and through a comprehensive, in situ study of the comet, Rosetta aims to unlock the secrets within.
Comets are time capsules containing primitive material left over from the epoch when the sun and its planets formed. Rosetta's lander will obtain the first images taken from a comet's surface and will provide the first analysis of a comet's composition by drilling into the surface. Rosetta also will be the first spacecraft to witness at close proximity how a comet changes as it is subjected to the increasing intensity of the sun's radiation. Observations will help scientists learn more about the origin and evolution of our solar system and the role comets may have played in seeding Earth with water, and perhaps even life.
Read the full story on NASA's website.