Philae lander successfully lands at Rosetta Comet

The lander successfully touched down on the comet at 10:35 am EST (Eastern Time Zone encompassing 17 U.S. states in the eastern part of the contiguous United States, parts of eastern Canada and three countries in Central America – which is 5 hours behind Coordinated Universal Time [UTC]) on Wednesday, Nov. 12. right on schedule!.... It took Philae 7 hours to descend to the comet's surface - one of the most difficult manoeuvres tried in space ~ and after those tense 7 hours, the scientists at the ESA and NASA started celebrating the historic touchdown of Philae lander.  The signal broke a seven-hour wait of agonising intensity and sparked scenes of jubilation at the European Space Agency’s mission control in Darmstadt. The team in charge of the Rosetta mission achieved what at times seemed an impossible task by landing a robotic spacecraft on a comet for the first time in history.

But celebrations were tempered by the later discovery that the probe’s two harpoons had not fired to fasten the craft down in the ultra-low gravity. Scientists now think the probe may have bounced after first coming into contact with the surface. Ulamec said: “Maybe today we didn’t just land once, we landed twice.” The safe, if precarious, touchdown of the lander gives scientists a unique chance to ride onboard a comet and study from the surface what happens as its activity ramps up as it gets closer to the sun.  Google too celebrates it with a nice doodle ….

Philae, the first probe that humans have ever landed on a comet, is already sending back images from its journey. Philae is a robotic European Space Agency lander that accompanied the Rosetta spacecraft until its designated landing on Comet 67P/Churyumov–Gerasimenko, more than ten years after departing Earth. On 12^th November 2014, the lander achieved the first-ever controlled touchdown on a comet nucleus. Its instruments are expected to obtain the first images from a comet's surface and make the first in situ analysis to determine its composition.

The lander is named after Philae Island in the Nile, where an obelisk was found and used, along with the Rosetta Stone, to decipher Egyptian hieroglyphics. Philae 's mission is to land successfully on the surface of a comet, attach itself, and transmit data from the surface about the comet's composition. The scientific goals of the mission focus on "elemental, isotopic, molecular and mineralogical composition of the cometary material, the characterization of physical properties of the surface and subsurface material, the large-scale structure and the magnetic and plasma environment of the nucleus.

The £1bn ($1.58bn) Rosetta mission aims to unlock the mysteries of comets, made from ancient material that predates the birth of the solar system. In the data Rosetta and Philae collect, researchers hope to learn more of how the solar system formed and how comets carried water and complex organics to the planets, preparing the stage for life on Earth. Space agencies have sent probes to comets before, but not like this. In 1986, Nasa’s Ice mission flew through the tail of Halley’s comet. In 2005, the agency’s Deep Impact spacecraft fired a massive copper block at comet Temple 1. But none before now has landed.

The feat marks a profound success for the European Space Agency (ESA), which launched the Rosetta spacecraft more than 10 years ago from its Kourou spaceport in French Guiana. Since blasting off in March 2004, Rosetta and its lander Philae have travelled more than 6bn kilometres to catch up with the comet, which orbits the sun at speeds up to 135,000km/h.  “Comets are the original source of Earth’s water. That wee lander is now in position, poised to re-write what we know about ourselves,” tweeted Chris Hadfield, the former Canadian astronaut and commander of the International Space Station.

Landing Philae on the comet’s surface was never going to be easy. When ESA managers got their first close-up of the comet in July, its unusual rubber duck shape left some fearing that a safe touchdown was impossible. The shape was not the only problem. The comet’s surface was hostile: hills and spectacular jutting cliffs gave way to cratered plains strewn with boulders. If Philae landed on anything other than even ground it could topple over, leaving it stranded and defunct. Rosetta spent weeks flying around the comet to create a surface map from which mission controllers could choose a landing site.  From a shortlist of five potential landing spots, scientists and engineers unanimously voted for a 1 sq km region on the comet’s “head” later named Agilkia. At the start of the mission, ESA officials had assumed the comet would be potato shaped and rated their chances of a successful landing at 75%. After seeing the shape and terrain of their target close up, those odds fell to around 50%, but climbed again as technical staff learned more about the landing site.For the mission team, the seven-hour descent, during which Philae fell at walking speed towards the comet’s surface, was a nail-biting experience.  Eventually, the  lander separated from its mothership  and touched down.

The lander could continue working until March next year, when the electronics will become too warm to work properly. Even when Philae packs up, it may still cling on to the comet, perhaps for several 6.45-year-long laps around the sun, before enough material erodes from the comet’s surface for the lander to lose its grip.

With regards – S. Sampathkumar

13^th Nov 2014.