This story was updated at
6:36 a.m.
DARMSTADT, Germany --
Europe's Venus Express probe entered orbit around Venus early Tuesday to begin a planned 16-month mission to study a planet on which the greenhouse effect has gone to hellish extremes.
The European Space Agency
(ESA) probe fired its main engine today for a 50-minute braking maneuver to
allow itself to be captured by the gravitational pull of Venus.
Venus Express managers at
ESA's mission control center here had loaded the engine-firing commands to the
satellite several days before, and had little more to do than watch their
screens and hope
the sequence went as planned.
It did. Using large ground
antennas located in Australia and Spain, ground teams confirmed that the engine
firing was a success. With the satellite 74 million miles (120 million
kilometers) from Earth, it took seven minutes for the satellite's signal to
reach ground teams, creating some tense moments here as the science and mission
teams waited for the satellite's signal.
"It's a
great day for ESA," said ESA director-general Jean-Jacques Dordain after Venus
Express' successful orbital arrival. "It's a happy day for all of us."
Tense times
During the orbital
insertion engine burn, Venus Express' trajectory took it behind its target
planet, meaning that for 10 minutes there were no radio signals available to
ground teams. The mission control center went
silent as ground teams waited to hear the return of the weak S-band signal from
the satellite.
"We were
sweating for a few minutes," said Manfred Warhaut, Venus Express flight
operations for the ESA, in a post-orbit arrival press conference.
Applause followed the
confirmation that the signal had been acquired anew. But there were 12 more
minutes of engine burn that were needed to further slow the satellite's speed
and confirm its capture by Venus.
Mission controllers applauded when the
signal confirmed that the engine had completed its burn and shut down, making Venus Express the first dedicated orbiter to study its cloudy target since NASA's Magellan mapping probe plunged into the planet's atmosphere in 1994.
"It's a fantastic
moment," said Don McCoy, Venus Express project manager at ESA. "We're
finally around Venus. The S-band signal tells us we are in orbit. If we didn't
get at least 46 minutes of engine burn, we basically would just fly past the
planet."
Venus Express' initial
nine-day orbit is designed to be highly elliptical ranging from an altitude
of between 248 miles (400 kilometers) and 217,479 miles (350,000 kilometers)
above Venus' surface, and gives the probe its only view of the entire
planet's disk during its mission, mission managers have said. Two more burns
will be conducted in the coming days to bring the orbit into its operational
altitude of between 155 miles (250 kilometers) and 41,010 miles (66,000
kilometers).
"This is
really a fantastic experience to see that we ended up in exactly the position we
wanted to be in," Venus Express project scientist Håkan
Svedhem said in the press conference. "Now our work starts."
Launched
in November 2005, the ESA's $264 million (220 million euros) Venus Express
mission is not expected to begin full operations until mid-May, but mission
managers will begin switching the probe's seven
observing instruments by Wednesday with the first image to arrive on Thursday,
ESA officials said.
A cloudy world
While Venus is about the
same age and size as Earth, it is 30 percent closer to the Sun.
Evidence from past
satellite missions - the United States and Russia have sent more than a dozen satellites
to Venus since the 1960s - shows that Venus once featured surface
water.
"We have many questions
surrounding Venus," Svedhem said, adding that the planet appears to have shared
much in common with Earth during its early days. "Why is Venus the way it is,
why is it not like Earth?"
For reasons not yet
understood, Venus' atmosphere built up huge amounts of carbon dioxide, which
trapped the sun's heat and drive temperatures to around 890 degrees Fahrenheit
(477 degrees Celsius). It is an extreme example of the same greenhouse effect
that operates on Earth, and scientists want to learn lessons from Venus that
might be of use on this planet.
"If you want to find
out about things on our own little planet, you have to look out," said
David Southwood, ESA's science director.
Venus Express was built by
a European consortium led by EADS Astrium, using hardware that was initially
designed for Europe's Mars
Express satellite. Instruments built for Mars Express and for Europe's Rosetta
comet-chaser satellite were reused on Venus Express as well.
Taking advantage of
previously used hardware helped speed Venus Express development. It took just
three years from the time the
manufacturing contract was signed to the launch of the satellite.
Initially designed for a 243-Earth
day - or two Venusian day - mission, Venus Express has enough fuel remaining to
double its time at the second planet from the Sun thanks to a spot on launch
from Earth, mission managers said.
"We have quite a good margin of fuel on board," McCoy said, adding that Venus
Express could study its cloudy target for up to six years if its extended
mission is approved. "Right from the very instance of separation from our
launcher, we've had an excellent trajectory to Venus."
SPACE.com Staff Writer
Tariq Malik contributed to this story from New York City.
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