Mission to Land on a Comet

Europe’s Rosetta spacecraft is en route to intercept a comet– and to make history. In 2014, Rosetta will enter orbit around comet 67P/Churyumov-Gerasimenkoand land a probe on it, two firsts.
Rosetta’s goal is to learn the primordial story a comet tells as it gloriously falls to pieces.
Comets are primitive leftovers from our solar system’s ‘construction’ about 4.5 billion years ago. Because they spend much of their time in the deep freeze of the outer solar system, comets are well preserved—a gold mine for astronomers who want to know what conditions were like back “in the beginning.”
As their elongated orbits swing them closer to the sun, comets transform into the most breathtaking bodies in the night sky. A European Space Agency mission launched in 2004 with U.S. instruments on board, Rosetta will have a front-row seat for the metamorphosis.
What we know of comets so far comes from a handful of flyby missions.
“In some ways, a flyby is just a tantalizing glimpse of a comet at one stage in its evolution,” says Claudia Alexander, project scientist for the U.S. Rosetta Project at JPL. “Rosetta is different. It will orbit 67P for 17 months. We’ll see this cometevolveright before our eyesas we accompany it toward the sun and back out again.”
Fierce solar heat will have a profound effect on Rosetta’s target. “We’ll watch the comet start as just a little nugget in space and then become something poetic and beautiful, trailing a vast tail.”
At the moment, Rosetta is “resting up” for the challenges ahead. It’s hibernating, engaged in its high-speed chase while fast asleep.
Reveille is on or around New Year’s Day 2014, when the spacecraft begins a months-long program of self-checkups.
If all goes well, in August of the same year, Rosetta will enter orbit around 67P’s nucleus and begin scanning its surface for a landing site. Once a site is chosen, the spacecraft will descend as low as 1 km to deploy the lander.
The lander’s name is “Philae” after an island in the Nile, the site of an obelisk that helped decipher—you guessed it—the Rosetta Stone.
Touchdown is scheduled for November 2014, when Philae will make the first ever controlled landing on a comet’s nucleus.
“When we land, the comet could already be active!” says Alexander. Because a comet has little gravity, the lander will anchor itself with harpoons. “The feet may drill into something crunchy like permafrost, or maybe into something rock solid,” she speculates.
Once it is fastened, the lander will commence an unprecedented first-hand study of a comet’s nucleus. Among other things, it will gather samples for examination by automatic onboard microscopes and take panoramic images of the comet’s terrain from ground level.
Meanwhile, orbiting overhead, the Rosetta spacecraft will be busy, too. Onboardsensors will map the comet’s surface and magnetic field, monitor the comet’s erupting jets and geysers, measure outflow rates, and much more. Together, the orbiter and lander will build up the first 3D picture of the layers and pockets under the surface of a comet.
The results should tell quite a story indeed….
Read more: science.nasa.gov


http://youtu.be/FoePrO4-fGQ

Most pristine known asteroid is denser than granite

The Rosetta spacecraft swung by asteroid 21 Lutetia on 10 July 2010

Asteroids are generally regarded as the solar system’s scrap heap, the battered bits that broke off and were left behind when the planets were forming. But the lumpy asteroid 21 Lutetia may be a whole, unbroken building block left nearly untouched since the solar system’s birth.

“We think planets were built of things like Lutetia,” says Ben Weiss of the Massachusetts Institute of Technology in Cambridge. “We’re getting a chance to see one of the building blocks of the solar system up close.”

The European spacecraft Rosetta zipped past Lutetia at 50,000 kilometres per hour in July 2010, snapping photos of a cratered world about 121 kilometres long. That makes it the second-largest asteroid ever visited by a spacecraft, next to 560-kilometre-wide Vesta.

Violent mêlée

Most of the asteroids to get visits from spacecraft are rubble piles, chunks of debris that were loosely held together by gravity. But Lutetia is so dense that it appears to have survived the violent mêlée of collisions in the early solar system intact.

“The real new thing is that it’s not a rubble pile, it’s a solid block of rock,” says Holger Sierks of the Max-Planck Institute for Solar System Research in Germany, lead author of a new paper reporting the observations. “It’s really a remnant from the early days.”

The rock has one of the highest asteroid densities ever measured, at 3.4 tonnes per cubic metre. That is denser than granite and suggests Lutetia might have heavy metals in its core.

‘Seeming contradiction’

For that to have happened, it must have melted in the past, allowing the heavy elements to sink to the centre. It could have done that if it formed within the solar system’s first million years, when there was enough radioactive aluminium-26 to melt the space rock.

Curiously, Rosetta’s optical instruments showed an unmelted surface covered in craters – providing no hint that its interior might be full of heavy metals. That hidden history of melting might explain a “seeming contradiction between the meteorite suite and the asteroids we see”, says Weiss.

Most asteroids look unmelted, but most meteorites that have fallen to Earth – thought to be fragments of asteroid cores – look like they have melted significantly. So it is possible that the melted meteorites are chips from space rocks that formed very early in the solar system, before the bulk of the radioactive aluminium – which has a half-life of 700,000 years – had decayed.

If Lutetia is a remnant from the solar system’s earliest days, what can we learn from it? Sadly, says Sierks: “We can’t really say much about the composition of the material. For that we really have to analyse in situ [with a lander] – or better, grab a piece and carry it back home for in-depth lab analysis.”
Journal reference: Science, DOI: 10.1126/science.1207325, 10.1126/science.1209389, 10.1126/science.1204062;
Planetary and Space Science, DOI: 10.1016/j.pss.2011.09.012
newscientist.com

Good night Rosetta: Comet chaser goes into deep-sleep….

….and won’t wake up until it reaches ice ball in 2014
A pioneering spacecraft that will land on a comet almost 600 million miles from Earth, has entered the loneliest leg of its mission.
Scientists at the European Space Agency have shut down most of the Rosetta probe’s systems placing the comet-hunter in to a long, dark hibernation.
The craft will now coast in silence for 31 months, looping its way into deep space until it wakes up in 2014 for arrival at its comet destination

The centre of the Milky Way galaxy and constellation Scorpius. In March, the comet happened to be located in this direction although it is invisible (red box)


The location of the comet: Rosetta takes a snap of its destination (in grey box) with its OSIRIS camera


Today’s event marks the end of the first phase of Rosetta’s ten-year cruise. It has already taken some impressive images of Earth, Mars and the Lucretia asteroid.
The deep sleep is necessary because the craft’s solar panels cannot
Rosetta is heading toward a rendezvous with 67-P/Churyumov-Gerasimenko, which is still some 100 million miles away.
Only the computer and several heaters will remain active. These will be automatically controlled to ensure that the entire satellite doesn’t freeze as its orbit takes it from 410 million miles from the Sun out to 490 million miles and back between now and 2014.
Today’s event marks the end of the first phase of Rosetta’s ten-year cruise. It has already taken some impressive images of Earth, Mars and the Lucretia asteroid.
The deep sleep is necessary because the craft’s solar panels cannot
Rosetta is heading toward a rendezvous with 67-P/Churyumov-Gerasimenko, which is still some 100 million miles away.
Only the computer and several heaters will remain active. These will be automatically controlled to ensure that the entire satellite doesn’t freeze as its orbit takes it from 410 million miles from the Sun out to 490 million miles and back between now and 2014.
‘We sent the command via NASA’s 70 m Deep Space Network station in Canberra, Australia, ensuring the signal was transmitted with enough power to reach Rosetta, which is now 549 million km from Earth,’ said ESA’s Spacecraft Operations Manager Andrea Accomazzo.
‘We’ll monitor via ESA’s 35m station at New Norcia in Australia for a few days to see if any problems occur, but we expect to receive no radio signal until 2014. Rosetta’s on her own now.’

2014: An artist's impression of the Rosetta Spacecraft reaching the comet 67-P/Churyumov-Gerasimenko


On 20 January 2014, a timer will wake the slumbering spacecraft, which will then transmit a signal to Earth to announce its revival.

 Mission controllers will then spend several weeks gradually warming up and reactivating the spacecraft in preparation for its rendezvous with the comet in July 2014.

Mission controllers at ESOC, ESA’s Space Operations Centre, Darmstadt, have spent most of the past year preparing for hibernation.
A special hibernation mode of the spacecraft was designed by engineers at EADS Astrium, the main industrial prime contractor that build Rosetta, to allow it to survive the large distances from the Sun during its cruise.

Asteroid encounter: Rosetta pictures the asteroid Lutetia during its closest approach on July 10, 2010


All of the scientific instruments were switched off by the end of March. In April and May, with Rosetta orbiting at more than 600 million km from the Sun, tests were conducted with the solar arrays to confirm that sufficient power would be available for today’s hibernation.

 Today Rosetta automatically started spinning just before the final shut-down command was sent, as this will stabilise the probe while the normal attitude control system is off throughout hibernation.

‘With flybys of asteroids Steins in 2008 and Lutetia in 2010, Rosetta has already delivered excellent scientific results,’ says Paolo Ferri, Head of ESOC’s Solar and Planetary Mission Operations Division.
‘Hibernation is a necessary step to reach the final target. We are now looking forward to 2014, when Rosetta becomes the first spacecraft to track the life of a comet as it arcs in toward the Sun.’
Read more: http://www.dailymail.co.uk/sciencetech/article-2001469/Good-night-Rosetta-Comet-chaser-goes-deep-sleep-wont-wake-reaches-ice-ball-2014.html#ixzz1OmoaQBKr