Rosetta’s Philae Lander Is About To Hitch a Ride on a Comet

The Rosetta spacecraft is a basically a big aluminum box. It has 11 scientific instruments mounted on top, subsystems mounted on the base, and a 7.2 foot-long high gain antenna sticking out on one side. Extending from both sides are two enormous solar panel wings each with a total “wingspan” of almost 105 feet. The remaining side of the spacecraft box is currently housing a 220 pound lander called Philae.

Also a box shape, the lander has small legs designed to effect a soft landing as well as rotate and lift the lander should it land on its target in a non-optimal attitude. And Philae’s target? The rather clunkily named Comet 67P/Churyumov-Gerasimenko.

Comet 67P/Churyumov-Gerasimenko is a regular visitor to the inner solar system, traveling once around the Sun once every 6.5 years on a path between the orbits of the Earth and Jupiter. Like so many comets, during its close passes by the Sun, Comet 67P/Churyumov-Gerasimenko warms up causing the ice on its surface to evaporate and jets of gas and dust to blast into the surrounding space. And on its next close solar pass, Philae will be on board with a front row seat.

Since its launch in 2004, Rosetta has circled the Sun five times, gathering energy from the Earth and Mars with every pass. All the while Philea has been sleeping, preparing for Rosetta’s encounter with Comet 67P/Churyumov-Gerasimenko. Now, it’s time for the little lander to wake up. On Jan. 20, it will power up, warm up, and reestablish communications with Earth.

The following four months will see Rosetta and Philae approach and rendezvous with the target comet, eventually slowing to a relative speed of about 6.5 feet per second. In August, Rosetta will map Comet 67P/Churyumov-Gerasimenko from about 124 miles away, gathering information on the comet’s spin-axis orientation, angular velocity, as well as major landmarks and characteristics.

Then in November the real fun begins. Once Rosetta picks a suitable landing site, it will fly to within three-quarters of a mile of Comet 67P/Churyumov-Gerasimenko and drop Philae. The lander will touch down at walking speed, or about 3.2 feet per second, before anchoring itself to its new host. Its first order of business will be to take high resolution pictures and gather data on the comet’s ices and crust. All the data will be relayed back to the Rosetta spacecraft, which will store it onboard until its next chance to transmit everything to receiving stations on the Earth.

From November of this year to December of 2015, Philae will ride on Comet 67P/Churyumov-Gerasimenko's back, watching and observing what happens as it approaches then flies away from the Sun. The mission will end when the comet leaves the inner solar system in two years; at that point Rosetta will make another pass by Earth.

This isn’t the first cometary exploration mission to have taken place. Among Rosetta’s notable predecessors are NASA’s Stardust mission that sampled dust particles from Comet Wild-2 in 2004 and Deep Impact that saw a projectile smash into Comet Tempel-1 in 2005, allowing the spacecraft to analyze the internal ejected material. But this is the first time a small lander will observe what happens to a comet on its close pass by the Sun from the surface of the comet itself. Not only are we sure to collect a trove of scientific data, Philae should be primed to return some absolutely incredible images.

@astvintagespace