background image
Andrea Accomazzo, ESA¡¯s Rosetta operations manager.
Rosetta¡¯s first images of 67P/Churyumov-Gerasimenko are expected in May, when the
spacecraft is still 2 million km from its target. Towards the end of May, the spacecraft
will execute a major maneuver to line up for its critical rendezvous with the comet in
August.
After rendezvous, Rosetta will start with two months of extensive mapping of the com-
et¡¯s surface, and will also make important measurements of the comet¡¯s gravity, mass
and shape, and assess its gaseous, dust-laden atmosphere, or coma. The orbiter will
also probe the plasma environment and analyse how it interacts with the Sun¡¯s outer
atmosphere, the solar wind.
Using these data, scientists will choose a landing site for the mission¡¯s 100 kg Philae
probe. The landing is currently scheduled for 11 November and will be the first time
that a landing on a comet has ever been attempted.
In fact, given the almost negligible gravity of the comet¡¯s 4 km-wide nucleus, Philae
will have to use ice screws and harpoons to stop it from rebounding back into space
after touchdown.
Among its wide range of scientific measurements, Philae will send back a panorama
of its surroundings, as well as very high-resolution pictures of the surface. It will also
perform an on-the-spot analysis of the composition of the ices and organic material,
including drilling down to 23 cm below the surface and feeding samples to Philae¡¯s
on-board laboratory for analysis.
The focus of the mission will then move to the ¡®escort¡¯ phase, during which Rosetta
will stay alongside the comet as it moves closer to the Sun, monitoring the ever-chang-
ing conditions on the surface as the comet warms up and its ices sublimate.
The comet will reach its closest distance to the Sun on 13 August 2015 at about 185 mil-
lion km, roughly between the orbits of Earth and Mars. Rosetta will follow the comet
throughout the remainder of 2015, as it heads away from the Sun and activity begins to
subside. (source: www.esa.int)
Rosetta Spacecraft Wakes Up From Deep Space Hibernation
¡°Incredible mission¡± will take comet exploration to new level
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It was a fairy-tale ending to a tense chapter in the story of the
Rosetta space mission on the evening of January 20, as the
European Space Agency (ESA) heard from its distant space-
craft for the first time in 31 months.
Rosetta is chasing down Comet 67P/Churyumov-
Gerasimenko, where it will become the first space mission to
rendezvous with a comet, the first to attempt a landing on a
comet¡¯s surface, and the first to follow a comet as it swings
around the Sun.
Since its launch in 2004, Rosetta has made three flybys of
Earth and one of Mars to help it on course to its rendezvous
with 67P/Churyumov-Gerasimenko, encountering asteroids
Steins and Lutetia along the way.
Operating on solar energy alone, Rosetta was placed into a
2014 February #5-1
deep space slumber in June 2011 as it cruised out to a distance of nearly 800 million km
from the warmth of the Sun, close to the orbit of Jupiter.
Now, as Rosetta¡¯s orbit has brought it back to within ¡®only¡¯ 673 million km from the
Sun, there is enough solar energy to power the spacecraft fully again.
Thus on January 20, still about 9 million km from the comet, Rosetta¡¯s pre-pro-
grammed internal ¡®alarm clock¡¯ woke up the spacecraft. After warming up its key
navigation instruments, coming out of a stabilising spin, and aiming its main radio
antenna at Earth, Rosetta sent a signal to let mission operators know it had survived
the most distant part of its journey.
The signal was received by both NASA¡¯s Goldstone and Canberra ground stations at
18:18 GMT, during the first window of opportunity the spacecraft had to communicate
with Earth. It was immediately confirmed in ESA¡¯s space operations centre in Darm-
stadt and the successful wake-up announced via the @ESA_Rosetta twitter account,
which tweeted: ¡°Hello, world!¡±
¡°We have our comet-chaser back,¡± says Alvaro Gim¨¦nez, ESA¡¯s Director of Science
and Robotic Exploration. ¡°With Rosetta, we will take comet exploration to a new level.
This incredible mission continues our history of ¡®firsts¡¯ at comets, building on the
technological and scientific achievements of our first deep space mission Giotto, which
returned the first close-up images of a comet nucleus as it flew past Halley in 1986.¡±
¡°This was one alarm clock not to hit snooze on, and after a tense day we are absolutely
delighted to have our spacecraft awake and back online,¡± adds Fred Jansen, ESA¡¯s
Rosetta mission manager.
Comets are considered the primitive building blocks of the Solar System and likely
helped to ¡®seed¡¯ Earth with water, perhaps even the ingredients for life. But many
fundamental questions about these enigmatic objects remain, and through its compre-
hensive, in situ study of Comet 67P/Churyumov-Gerasimenko, Rosetta aims to unlock
the secrets contained within.
¡°All other comet missions have been flybys, capturing fleeting moments in the life
of these icy treasure chests,¡± says Matt Taylor, ESA¡¯s
Rosetta project scientist. ¡°With Rosetta, we will track the
evolution of a comet on a daily basis and for over a year,
giving us a unique insight into a comet¡¯s behaviour and
ultimately helping us to decipher their role in the forma-
tion of the Solar System.¡±
But first, essential health checks on the spacecraft must
be completed. Then the eleven instruments on the orbiter
and ten on the lander will be turned on and prepared for
studying Comet 67P/Churyumov-Gerasimenko.
¡°We have a busy few months ahead preparing the space-
craft and its instruments for the operational challenges
demanded by a lengthy, close-up study of a comet that,
until we get there, we know very little about,¡± says
Artist impression of Rosetta¡¯s signal being received on Earth af-
ter 31 months in silent, deep space hibernation. The signal was
received at 18:18 GMT/ 19:18 CET by both NASA¡¯s Goldstone
and Canberra ground stations. Image: ESA-C.Carreau
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