Hibernating spacecraft Rosetta to awaken for comet chase
At 10am on Monday morning the spacecraft Rosetta will wake up from its deep space slumber and power-up so it can begin chasing a comet and fulfill its 10 year mission to land a probe on its surface.
By Sarah Knapton, Science Correspondent
7:00AM GMT 19 Jan 2014
It has been sleeping quietly in space for more than two and a half years.
But at 10am tomorrow an internal alarm will awaken the Rosetta spaceship, allowing scientists to begin one of the most technologically advanced missions ever attempted.
Put simply researchers are trying to catch a comet.
Over the next few months Rosetta will chase down 67P/Churyumov-Gerasimenko before harpooning the frozen ball of dirty ice and attempting to make a soft landing on its surface.
“It will be an amazing achievement for human endeavour, an 'Armageddon’ type thing,” said project scientist Matt Taylor at the European Space Agency, referring to the Bruce Willis film in which Willis lands on an asteroid to save the world from imminent destruction.
“We’re not just landing on the Moon, we’re dealing with something dynamic, which is kicking off tonnes of dust and gas every minute.”
The comet is currently hurtling through space at 24,600 miles per hour and its nucleus is only 2.5 miles wide.
Scientists compare the task to a fly trying to land on a speeding bullet. It is the stuff of science fiction, but it’s - hopefully - about to become science fact.
Comets are the primitive building blocks of the Solar System, left over from a planet-building time when our Sun was just a disc of spinning dust and gas.
Made of ice, dust and small rocky particles, it is likely they delivered the first water to Earth and may have even seeded the planet with the building blocks for life.
Cometary dust brought back to Earth by NASA’s stardust mission contained glycine, an amino acid that is a basic part of our DNA.
“We look at comets as being a time capsule, they are relics from the beginning of the solar system,” said Taylor, “We felt we had to go to one.”
Rosetta has already been travelling for more than a decade after the craft was launched on March 2 2004, from Kourou, French Guiana.
But the comet is moving far faster than speeds which could ever be achieved by a space ship leaving Earth. So the craft has spent the time since, using the gravitational pull of the Earth and Mars to act as a sling shot and allow it to pick up acceleration.
When it reached the crucial speed in July 2011 the spacecraft was put into deep-space hibernation for the coldest, most distant leg of the journey as it travelled some 497 million miles from the Sun, close to the orbit of Jupiter as the comet headed into outer Solar System.
Scientists extended its solar arms to catch the Sun’s rays and placed in a slow spin to maintain stability. The only devices left running were its computer and several heaters.
Thirty-one months on, Rosetta’s orbit has brought it back to within 418 million miles of the Sun, and there is finally enough solar energy to power the spacecraft fully again.
Now Rosetta’s internal alarm clock is set to rouse the sleeping space craft at 10am tomorrow so that it is ready to catch the comet when it returns to the inner solar system. There are also three back up alarm clocks, should the spaceship choose to hit the snooze button.
Once the 6,600 lbs craft wakes up, it will first warm up its navigation instruments before spinning around to point its main antenna at Earth, to let the ground team know it is still functioning.
Scientists are likely to face an eight hour wait before the first vital signs are beamed back to earth.
Because of Rosetta’s distance – just over 501 million miles from Earth – it will take 45 minutes for the signal to reach the ground stations. The first opportunity for receiving a signal on Earth is expected between 5.30pm and 6.30pm tomorrow.
Fred Jansen, ESA’s Rosetta mission manager, said: “We’re very excited to have this important milestone in sight, but we’ll be anxious to assess the health of the spacecraft after Rosetta has spent nearly 10 years in space.”
Mr Taylor said: “It’s sort of similar to putting the TV on standby for three years and expecting it come back on when you pressed the remote.”
After wake-up, Rosetta will still be about 5.6 million miles from the comet. But by May it will just 1.2 million miles from its target and scientists expect to be able to make final calculations about the comet’s position and orbit.
After extensive mapping of the comet’s surface during August and September, a landing site for the mission’s 220 lbs Philae probe will be chosen.
“One of the main problems is how we are going to stick to the comet. It has a weak gravitational field, so as it touches down harpoons will fire to keep the lander in position,” said Mr Taylor.
Philae, is around 35 cubic feet in size and is named after an island on the river Nile, where an obelisk was found containing an inscription which played an important role in deciphering the hieroglyphics on the Rosetta stone.
The lander will send back a panorama of its surroundings and high-resolution pictures of the surface and will perform analysis of the composition of the ices and organic material.
A drill will take samples from 8-11 inches below the surface, feeding them to Philae’s laboratory for analysis. Rosetta will then stay alongside the comet as it moves closer to the Sun.
Instruments on board will analyse the gases of the tail; probe the comets interior; measure dust grains and study its atmosphere and gravity.
The comet will reach its closest distance to the Sun on 13 August 2015 at about 115 million miles, roughly between the orbits of Earth and Mars. Even if the lander is still on the comet by then its instruments will have been rendered useless due to the heat of the Sun.
The £1 billion project will see Rosetta follow the comet throughout the remainder of 2015, as it heads away from the Sun and activity begins to subside.
“This will give us a unique insight into how a comet 'works’ and ultimately help us to decipher the role of comets in the formation of the Solar System,” added Mr Taylor.
“We used to look at the moon and then we went there. We saw comets and now we will have gone there.”
http://www.telegraph.co.uk/science/spac ... chase.html
Various diagrams on page.