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| March 9 Rosetta was 45 miles from Comet 67P/C-G when it photographed the comet’s head ringed with a halo of gas and dust. These jets extend from active areas of the comet’s surface and will become much more prominent over the next few months as the comet approaches the sun. |
Excerpt from dailytimesgazette.com
Astronomers have been on a mission to tail a slow moving comet in the outer space. Their mission started early last 2014, and they are getting better observations than they thought they would.
The comet, Comet 67P, would take 12.4 hours to complete one rotation in the circular path it’s moving in. Controllers of Rosetta are noticing that the icy ball approximately a second every day before it completes a rotation. The flight director of Rosetta – Andrea Accomazzo, said that, “The gas jets coming out of the comet, are acting like thrusters and are slowing down the comet.”
During the Royal Aeronautical Society in London earlier this week, the European Space Agency officially revealed some juicy details on how their team learned to maneuver Rosetta to fly precisely around the massive astral body. Comet 67P is said to weigh 10-billion tons with 4-km size in width.
The controllers and navigators use the landmark-method on the comet to understand its rotation. The team is moving around the outer space relying only on the information provided by the model. Both the model and information guides them in accurately projecting the trajectory of the satellite in the best position.
As they were trying out the model, the ESA team noticed that the landmarks were not following the usual track at the expected time.
During September 2014, the team were determined and very convinced that comet’s rotation period lengthen by 33 milliseconds per day. At present, the comet is approaching the Sun. As it does, it releases great volumes of gas and dust as a result of the so-called Spin-Down effect; further lengthening the rotation period to a second per day.
Accomazzo clarified that Comet 67P is not going to slow down in a slow motion. But its current speed allows them achieve the great magnitude of accuracy in navigating the spacecraft around the comet.
Rosetta made significant observations of the comet last December and January as it moves like an orbit within 30 km distance from the comet. However, this movement is no longer going to happen because Rosetta has retreated from the comet as the gas and dust are being released.
But it does them well as Accomazzo said that, “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 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.”
The trackers were confused during the recent weeks because they have mistaken the dust particles for stars. It was due to the fact that the dusts in the atmosphere were moving around the comet.
Now, Rosetta is using its propulsion system to move in a hyperbolic orbital rotation around Comet 67P. It approaches the comet no closer than 60 to 70 km. With the slowdown of the comet, the ESA team is planning to fly closer.
They were estimating a flight as close as 20 km to get a better look at the surface of the comet and find their lost landing probe, Philae. They lost contact with the robotic probe since November 12 due to lost battery power only days after it successfully landed on the comet.
The slowdown gives them an opportunity to search for Philae. As it moves closer to the Sun, lighting conditions are definitely better than their previous runs. The controllers are now calling onto Philae using radio shout outs.
Philae is solar powered so the team hopes that enough solar energy falls on the panels awaking the probe. But one problem still persist, “The problem is that even if Philae hears Rosetta, it has to have enough charge to turn on its radio transmitter.”
The flight director is quite doubtful if Philae will be awakening. Andrea suggested, “I put it at 50-50, but I will be the happiest person in the world if it happens,”
Their mission achieved great progress and observation of a comet. The team is wishing for better things as the 67P slow down leaving them with more advantage
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