It is a regular practice for most of us to get ready for the
day at the buzz of an alarm. But is a moment
of incredible trepidation when the European Space Agency (ESA)’s spacecraft
Rosetta woke up after a gap of 31 months at the buzz of its preset alarm to
begin its rendezvous in space. What makes science so interesting is not just
the labyrinth of the technology but the huge amount of excitement in can
invigorate in researchers and science enthusiasts.
The International Rosetta Mission was approved in November
1993 by the ESA’s Science Programme Committee as part of Planetary Corner Stone
Mission in ESA’s long term space Science Programme. The mission was originally
scheduled for a rendezvous with the comet 46 P/Wiratenin but due to
postponement of launch of the space craft twice, the new target is comet 67 P/
Churyumov-Gerasimenko. Comet was named after the discoverers Klim Churyumov and
Svetlana Gerasimenko who first indentified it in September 1969. The mission
has been aptly named after Rosetta Stone, the slab of volcanic basalt which
provided the key to unravelling the Egyptian hieroglyphs. Scientists hoped that
this mission would unfold the mysteries of oldest building blocks of solar
system- Comets. Rosetta is a robotic spacecraft launched on March 2004 by the
Ariane 5 rocket. It has two main elements: the Rosetta Space probe orbiter
which harbours 12 instruments and Philae, a robotic lander with additional 5
instruments. It is designed to both
orbit and land on the comet to have the most detailed study of comet. During
its 10 year long voyage it made three flybys of earth and one flyby of Mars in
2007. It has passed by two asteroids: 2867 Steins in 2008 and 21 Lutetia in
2010. The spacecraft entered deep space hibernation mode when instruments have
been powered down to conserve energy in June 2011. It was programmed to remain
in that state till 20th Jan 2014 when the hibernation exit will be initiated.
All the operations are controlled from the European Space Operations Centre
(ESOC) Darmstadt, Germany
Comets are the small icy bodies which originate either in the
Oort Cloud that exist far beyond the orbit of the Pluto or from the Kuiper Belt
located beyond the orbit of Neptune and releases gas or dust. When comets pass
close to the sun they get heated up and begin to outgas thus displaying visible
atmosphere or Coma and sometimes a tail. Usually the dust consists of ice, carbon
dioxide, ammonia, methane and more. Scientists believe that comets might have
brought water and other organic molecules to earth which led to initiation of
life on earth. Comet 67 P are believed to have originated from Kuiper belt and
are controlled by Jupiter’s gravity. Hence they are called the Jupiter Family
Comets. Due to collisions or gravitational perturbations these icy bodies are
ejected from the Kuiper belt and fall towards sun. When these comets cross the
orbit of Jupiter and interact with it their orbits gradually change. Comet 67 P
whose perihelion was 4 AU (Astronomical Unit or the distance between the Sun
and earth) in 1840 has come closer to sun due to a fairly close encounter with
Jupiter in 1959 and slipped to 1.27 AU,
following which its distance has changed a little. The robotic lander Philae of
Rosetta is going to land on the surface of the comet from the sunward side of
the orbit so that it would encounter less dust and with a low probability of
being disabled by large impact.
The succeeding events post-hibernation have been meticulously
planned. In May 2014, the spacecraft will enter a slow orbit around the comet
and gradually slowdown in preparation for landing. The lander will approach the
comet at a speed of 3.6kmph and upon contact with the comet, two harpoons will
be fired into the comet to prevent the lander from bouncing off the surface
comet. Still very little is known about
surface properties of the comet are known. Hence after the detailed mapping in
August 2014, the exact site of landind will be decided. Rosetta will land on
comet in November 2014 after which it will
escort the comet around the sun. The mission will be annulled in December 2015.
Currently Rosetta is 800 million kilometres away from earth.
The radio transmission signals travelling at a speed of light takes 45 minutes to
reach the nearest Gold Stone radio dish in California. The spacecraft is at a
distance of 9 million km from comet and this would be gradually reduced to 10km
by September 2014 by series of burns on its thrusters and by November 2014 the
three-legged Philae will land on the comet.
Cometary explorations began in 1978 with the launch of NASA’s
International Cometary Explorer, passed the tail of Comet Giacoinni-Zinner and
Comet Halley. Followed by two Russian probes, Vega-1 and Vega-2 in 1984;
Japanese twin spacecrafts Sakigake and Suisei (1985); ESA’s Giotto in 1985.
NASA’s missions include- Deep Space 1(1998), Stardust (1999), Contour (2002),
Deep Impact (2005) which was retired in 2010. Rosetta is the first mission ever
attempting to land on the nucleus of comet.
Till now the mission had successfully carried out its
objectives of global characterisation of asteroids, including determination of
their dynamic properties, surface morphology and composition. Rosetta is
gearing up for the final leg of studying comets, also referred to as dirty
snowballs. They are believed to contain materials that have remained largely
unchanged since the formation of solar system 4.6 billion years ago. Further
the enticing analysis of the comet dust in 2006 brought by the Stardust mission
of NASA revealed presence of several interesting molecules and an amino acid
Glycine, which is an important component of many enzymes, receptors and DNA. Amino
acids can be right-handed or left-handed. But left-handed amino acids are alone
used in life on earth. Hence analysing the composition of comets can provide an
answer or give a hit that may be life or the ingredients of life may have been
brought to earth from extraterrestrial space. Thus, this mission is
extraordinary for its miraculous adventures in space and for overwhelming exhilaration
it is set to generate.
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