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Unexpected
detail in first-ever Venus south pole images
13 April 2006
Composite,
false-colour view of Venus south pole captured by VIRTIS 12
April 2006 onboard Venus Express.
Credits: ESA/INAF-IASF,
Rome, Italy, and Observatoire de Paris, France
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ESA's Venus Express has
returned the first-ever images of the hothouse planet’s
south pole from a distance of 206 452 kilometres, showing
surprisingly clear structures and unexpected detail. The images
were taken 12 April during the spacecraft’s initial capture
orbit after successful arrival on 11 April 2006.
Engineers
have lost no time in switching on several of the instruments and
yesterday the VMC (Venus Monitoring Camera) and VIRTIS (Visible
and Infrared Thermal Imaging Spectrometer) imaged, for the first
time in space history, the southern hemisphere of Venus as the
spacecraft passed below the planet in an elliptical arc.
Scientists are especially
intrigued by the dark vortex shown almost directly over the south
pole, a previously suspected but until now unconfirmed structure
that corresponds to a similar cloud structure over the north
pole. “Just one day after arrival, we are already
experiencing the hot, dynamic environment of Venus,” said
Dr Hakan Svedhem, Venus Express project scientist. “We will
see much more detail at an unprecedented level as we get over 100
times better resolution as we get closer to Venus, and we expect
to see these spiral structures evolve very quickly.”
The
initial, low-quality images were taken from an extreme distance
of 206 452 kms from the planet, yet caught scientists’
attention, particularly with the surprisingly clear structures
and unexpected details shown in the VIRTIS spectrometer
images.
The false-colour VIRTIS composite image
shows Venus’s day side at left and night side at right, and
corresponds to a scale of 50 kms per pixel.
The day
half is itself a composite of images taken via wavelength filters
and chiefly shows sunlight reflected from the tops of clouds,
down to a height of about 65 km above the planet’s surface.
Dynamic spiral cloud structures
False-colour
view imaged in ultraviolet of Venus south pole captured by
VMC 12 April 2006 onboard Venus Express.
Credits:
ESA/MPS, Katlenburg-Lindau, Germany
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The more spectacular night
half, shown in reddish false colour, was taken via an IR filter
at a wavelength of 1.7 microns, and chiefly shows dynamic spiral
cloud structures in the lower atmosphere, around 55 km altitude.
The darker regions correspond to thicker cloud cover, while the
brighter regions correspond to thinner cloud cover, allowing hot
thermal radiation from lower down to be imaged.
The smaller VMC image
shows Venus at a scale of 150 kms per pixel and is also shown in
false colour. It was recorded in ultraviolet.
Venus
Express fired its main engine to enter Venus orbit on 11 April
2006 and is now in the first 9-day capture orbit taking it to
apocentre (maximum height) at 350 000 kilometres below the south
pole. It will swing back up to pass pericentre (minimum height)
at an altitude of 250 kilometres over the planet’s north
pole.
Towards the 24-hour final orbit
In
the first capture orbit, Venus Express will have 5 additional
opportunities for gathering data until reaching pericentre. These
observations represent a great opportunity because, at apocentre,
the full disc of Venus is fully visible for the spacecraft’s
imagers. Such opportunities will not occur again during the
nominal mission, starting on 4 June 2006, when the range of
distances from the planet will be much smaller.
View
imaged in ultraviolet of Venus south pole captured by VMC 12
April 2006 onboard Venus Express.
Credits: ESA/MPS,
Katlenburg-Lindau, Germany
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In addition to VMC and
VIRTIS, the spacecraft’s MAG (Venus Express Magnetometer)
has been switched on for initial verification and is operating
nominally. Together with the ASPERA (Analyser of Space Plasma and
Energetic Atoms), the two instruments are expected to gather
information about the unperturbed solar wind and the atmospheric
escape processes on Venus, a planet with no magnetic protection.
A series of further engine and
thruster burns are planned to gradually reduce the apocentre
during the following 16 orbital loops around the planet and the
spacecraft is due to attain its final 24-hour polar orbit on 7
May, ranging from 66 000 to 250 kilometres above Venus.
Source
/ Credit: ESA
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