As Rosetta homes in on its target – Comet 67P, they’ve noticed that this ball of ice spends an extra second each day completing its 12.4 hour rotation. According to the craft’s flight director Andrea Accomazzo: “The gas jets coming out of the comet, are acting like thrusters and are slowing down the comet.”
At the Royal Aeronautical Society which happened in London this week, the European Space Agency (ESA) disclosed some of the ways that their craft maneuvered around this celestial body. Comet 67P is estimated to weigh 10-billion tons, and is 2.5 miles wide.
Accomazzo revealed that Comet 67P will not slow down gradually, lengthening its rotation due to a spin-down effect as it nears the sun, releasing substantial gasses. Gauging the current speed allows a great window for accuracy when navigating around the comet.
Significant observations were made through December and January when it orbited just 18 miles away from the comet.
According to Accomazzo: “The aerodynamic effects are now more and more important. The jets are getting stronger and stronger… To give you an idea, these gases come out of the comet for a few kilometers and are moving at 800 meters (2,624 feet) per second. We definitely have to take this into account. We are a big spacecraft with 64 square meter s of solar panels. We’re like a big sail.”
Now, Rosetta makes use of a propulsion system, in order to make a hyperbolic orbital rotation around Comet 67P. As the comet is slowing down, however, they hope to move in closer – a goal of getting within 12 miles of the comet in order to spot the Philae lander, which they lost contact with after it fell into a crater and gradually lost battery power.
As they get closer, however, they will also have the benefit of lighting conditions, and are currently “shouting out” to the lander with radio technology.
Because Philae runs on solar power, the team is hoping for enough solar energy to hit the panels and revive the probe. There is one small problem, however: “The problem is that even if Philae hears Rosetta, it has to have enough charge to turn on its radio transmitter.”
The flight director remains uncertain that the lander will awaken. “I put it at 50-50, but I will be the happiest person in the world if it happens,” she said.