A European
probe bearing down on the planet Venus is set for a Tuesday arrival to take a
close look at the world's soupy atmosphere.
After five
months of spaceflight,
the European Space Agency's (ESA) Venus Express orbiter is expected to fire its
main engine in a nearly hour-long maneuver to begin its planet-watching duties.
"I don't
dare get too excited because we have to be calm if there are any problems," Venus
Express project manager Don McCoy told SPACE.com. "It will feel good
once we know we're in orbit around the planet."
The ESA launched
the $226 million (220 million Euro) Venus Express mission spaceward in November
2005 on what the space agency has billed its fastest mission to fly. Not since
NASA's Magellan
mission ended with the spacecraft's death plunge into the Venusian thick
atmosphere in 1994 has the planet had a dedicated orbiter around it.
"It's getting
very close and everything is working well, so that is comforting," said Håkan Svedhem, Venus Express project scientist, in a
telephone interview.
The
2,799-pound (1,270-kilogram) Venus Express spacecraft is expected to fire its
main engines for 51 minutes beginning at 3:17 a.m. EDT (0717 GMT) Tuesday to
place itself on the proper orbital trajectory.
By the
maneuver's end the spacecraft is expected to be flying in an orbit that reaches
248 miles (400 kilometers) above the Venusian surface at its low point and
about 217,479 miles (350,000 kilometers) at the high end, mission managers
said.
"It's
a very eccentric orbit," said McCoy, adding that it should take Venus Express a
full nine days to complete its first orbit while observing the planet. "It's
the only time during the entire mission that we'll be able to see the entire
planetary disk."
Unveiling
Venus
Venus
Express carries seven
primary instruments, many of which were spares left over from previous ESA
missions such as the agency's Mars
Express and comet-bound Rosetta
programs, to peel back the layers of the Venusian atmosphere. Researchers hope
the spacecraft will unveil
the source of Venus' dense, turbulent and toxic atmosphere.
"We think
that volcanism is the mechanism that would produce that atmosphere," Svedhem said. "And if we find that this is the case, well that
I think would be very exciting."
Svedhem and his colleagues also hope to better understand how
trapped carbon dioxide, water vapor and sulphuric aerosol gases factored into
the "greenhouse effect" that appears to superheat Venus' atmosphere to an
average temperature of about 869 degrees Fahrenheit (465 degree Celsius).
Venus
Express is expected to begin its primary science mission - a 15-Earth month
period that translates into two of Venus' long sidereal days - in June after a
series of maneuvers to reach its final operational orbit.
"It's just
straight propulsion," McCoy said of the orbital posturing, adding that unlike
NASA's Mars Reconnaissance Orbiter - which is currently using Mars' atmosphere
to shape its orbit in a process called aerobraking
- Venus Express will rely solely on its engines. "It's lot faster than
aerobraking and, in that sense, it's easier."
Venus
Express' transit to its target planet required less of the probe's 1,256 pounds
(570 kilograms) of fuel than anticipated, allowing for some leeway in the
process, ESA officials said.
"In
principle, we're all ready to go," McCoy added.
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