[meteorite-list] Rosetta Soars on Ambitious Comet Intercept Mission

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:32:45 2004
Message-ID: <200403021632.IAA16620_at_zagami.jpl.nasa.gov>


Rosetta soars on ambitious comet intercept mission
March 2, 2004

Embarking on its epic voyage to gain new insights into comets and the history
of our solar system, the Rosetta spacecraft was successfully launched today to
rendezvous with a cosmic snowball and deploy a tiny lander onto its icy heart.

The Ariane 5 rocket fired up at 0717:44 GMT (2:17:44 a.m. EST),
exactly when the booster could place the probe on the first leg of its
ten-year course to comet Churyumov-Gerasimenko.

The Ariane solid rockets and first stage put Rosetta on an arcing
suborbital ballistic trajectory about ten minutes after launch. The
upper stage's Aestus engine fired nearly two hours after liftoff to send
the 6,700-pound craft out of Earth's grasp and into solar orbit.

Rosetta aims to give scientists a wealth of knowledge about comets,
frozen time capsules from billions of years ago, while helping the
public at large wrestle some of the most fundamental questions that
humans can ask.

"I think it is very hard to imagine that you don't wonder sometimes what is it all
about? Where did it all come from?" says European Space Agency science
director David Southwood. "Once we were all star dust. How did we turn out to
be the complicated beings that we are now? I think we are looking for some of
the clues that will help us put that story together."

Today's launch has been in the works since the Rosetta project began in 1993.
Since then, the Rosetta team has been thrown a number of curves -- most
recently the decision to delay the launch from January 2003 due to concerns with
the reliability of the Ariane 5 rocket.

Delaying the launch from 2003 to 2004 caused managers to change
targets for the probe, which required extensive studies of
Churyumov-Gerasimenko to see if it was suitable to approach with a
$1 billion spacecraft and safe to land upon with a tiny robot

Rosetta will take a circuitous route through the solar system and will
arrive back in the vicinity of Earth next March for its first crucial
gravity assist fly-by. The probe will reach Mars in March 2007, followed
by two additional close approaches of Earth to tweak its course toward

Heading further from the Sun and past the asteroid belt, Rosetta will
fly near several of these space rocks and study them from a distance of
over a thousand miles before entering a hibernation period in mid-2011.

"These brief encounters are a scientific opportunity and also a chance to
test Rosetta's instrument payload," explained Rosetta project scientist
Gerhard Schwehm from the European Space Agency.

For two-and-a-half years, Rosetta's systems will be completely shutdown
with the exception of its primary computer and radio receivers in order to
conserve power. Fitted with two solar wings spanning almost 100 feet, the
spacecraft will be the first to fly near the orbit of Jupiter and rely
entirely on solar power.

"To provide the probe with the power it needs in space, we have given it the
biggest solar panels ever carried by a European satellite," said Manfred
Warhaut, Rosetta's operations manager.

Rosetta will also undergo a number of other extended periods of inactivity
between key mission events during the journey to Churyumov-Gerasimenko to
relieve manpower and electrical constraints.

Power production is strained for Rosetta because it will be traveling over 500
million miles from the Sun, where light levels are only four percent of those
found on Earth.

Controllers will bring Rosetta back to life in early 2014 for a thruster
firing to slow the probe's approach to the comet before entering orbit
and beginning its mapping and scientific mission to characterize the surface.

"Rosetta carries more instruments than any previous scientific spacecraft --
that makes it challenging and one of the most exciting missions ever," said
Claudia Alexander, U.S. project scientist for the mission from NASA's Jet
Propulsion Laboratory. "We anticipate major discoveries, just like Galileo and

By the end of the summer in 2014, Rosetta will be in orbit around
Churyumov-Gerasimenko and science operations should be in full swing. A
major priority will be the determination of favorable landing sites for a small
220-pound lander carried aboard Rosetta named Philae.

The three-legged Philae will touch down on the surface in November 2014,
firing a harpoon to keep the tiny craft anchored on the comet so it doesn't float
away in the weak gravitational field. It will snap high-resolution pictures and
acquire data about the comet's organic crust and molecules for transmission up
to the orbiter for later relay to Earth.

Operating at least one week, perhaps significantly longer, Philae's instrument
suite even includes a tiny drill that can bore a few inches into the comet for
subsurface investigations.

Together the orbiter and lander will observe the traits and changes the comet
goes through as it approaches the Sun. Officially, the mission is slated to come
to conclude in late 2015.

"This will be our first ever chance to be there, first hand, so to speak, as a
comet comes to life," Schwehm said. "As we will be accompanying
Churyumov-Gerasimenko for two years, until the comet reaches its closest
point to the Sun and travels away from it, we can at long last hope to acquire
new knowledge about comets."

Comet Churyumov-Gerasimenko was discovered in 1969 and is considered a
dusty comet that is roughly two by three miles in diameter. The Hubble Space
Telescope was chartered to observe the comet for 21 hours in March 2003 to
gather more specific details about Churyumov-Gerasimenko to allow project
officials to decide whether to pursue it as a potential target.

"This comet has only about three-hundred-thousandths the gravity of Earth,"
said Alexander. "The Rosetta spacecraft will be able to make observations from
as close as 2 kilometers (1.2 miles). The data from our state-of-the-art
instruments will be amazing."

Scientists believe comets are made of the very same primitive materials that
were present when the Sun and the solar system were formed an estimated 4.6
billion years ago.

Comets are balls of ice and rock believed to be formed far beyond the orbit of
Pluto where conditions are cold and dark, much like they were as the solar
system was born. Some of these objects are drawn toward the inner solar
system and they become comets -- giving us a unique view of almost the same
primordial materials that played such important roles in the formation of the Sun
and the planets.

"They are the keys to understanding the way the whole solar system, the
Earth, and how even we came into being. And with Rosetta we will be able to
observe, study and analyze this primordial material up close for more than a
year," said Paul Weissman of NASA's Jet Propulsion Laboratory.

"We are confident we will come a step nearer to understanding the origins and
formation of our solar system and the emergence of life on Earth," said

Rosetta gets its name from the stone tablet found by French soldiers in Egypt
in 1799 that contained the key to deciphering Egyptian hieroglyphics. Scientists
hope this mission may unveil the mysteries surrounding how our planet and life
came to be as we know it today.

ESA managers are not lost on the difficulties associated with the mission.

"Rosetta is one of the most challenging missions undertaken so far. No one has
ever attempted such a mission, unique for its scientific implications as well as
for its complex and spectacular interplanetary space maneuvers," Southwood

"This mission will turn science fiction into science fact. Every aspect of comet
Churyumov-Gerasimenko will be analyzed, resulting in the most
comprehensive set of scientific measurements ever obtained of a comet," said
Professor Ian Halliday, chief executive of the Particle Physics and Astronomy
Research Council, which funded two of the instruments.
Received on Tue 02 Mar 2004 11:32:55 AM PST

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