Andrew Yee[_1_]
May 17th 07, 04:35 AM
ESA News
http://www.esa.int
7 May 2007
Venus Express' infrared camera goes filming
An exciting new series of videos from ESA's Venus Express has been capturing
atmospheric details of day and night areas simultaneously, at different
altitudes.
The south pole of the planet and its gigantic double vortex has been
pictured as never before.
The south pole of Venus and the double-eyed storm permanently rule
atmospheric phenomena in that area of the planet. They are key to
understanding the global atmospheric dynamics on Venus and will contribute
to a better comprehension of the global meteorology of the planet.
In the search for all possible clues on how to solve the global atmospheric
'puzzle', the team of scientists behind the Ultraviolet, Visible and
Near-Infrared Mapping Spectrometer (VIRTIS) on board Venus Express, have
tried something new -- starting from the south pole.
They started by focusing on this target from the advantageous position of
the orbit apocentre (the furthest distance of the spacecraft from the
planet). This allows the instrument to keep the target in the field of view
for longer than in other portions of the orbit, where the spacecraft travels
faster. In this favourable position, scientists made efficient use of the
multi-wavelength capability of VIRTIS.
By using wavelengths longer than 3 microns in the thermal infrared range,
VIRTIS can obtain a combined view of the day and night sides simultaneously.
This is more convenient since at shorter wavelengths, the difference between
the thermal radiation emitted on the day and night sides is too high to
observe both regions simultaneously without 'blinding' some channels of the
camera.
"It is comparable to looking at bright, sun-illuminated snow and at a dark
sky without having to change your glasses," said Giuseppe Piccioni, VIRTIS
co-Principal Investigator. "In addition, within this observation process,
not only can we look at the dark and lit sides of the south pole at the same
time, but we can also look into the atmosphere at different depths. What we
are building is the most complete 3D data set of the Venusian atmosphere to
date."
The VIRTIS videos of the south polar vortex presented here are the result of
combined observations at two different wavelengths (3.8 and 1.7 microns,
respectively) used at the same time. The various images were taken over five
orbits, during a time-span of about 8 hours per orbit.
The 3.8-micron channel was chosen because of its compatibility (in exposure
time) with the 1.7-micron observations, as well as for its capability to
provide information about the cloud deck at about 65 kilometres altitude
over the planet. The 1.7-micron wavelength was chosen to probe the
atmosphere below the clouds when looking at the night side.
It is clearly possible to see that the morphology of the vortex changes a
lot during the 8-hour observation session and from one orbit to the next
(one Venus Express orbit is 24 hours long).
It is interesting to note that due to 'bad weather conditions', by the time
of the observations, the videos do not show the maximum achievable image
contrast. In fact, the visibility of the polar structure was somewhat
reduced by the local increase of the upper atmospheric haze.
"If the weather permits, by extending the time span of our future
observations, we may have the chance to obtain even clearer and more
detailed views of the polar vortex," added Piccioni.
"With video sequences of this kind, combining all the pieces of information
together, we can study the dynamics and the evolution of the vortex both in
the short and the long term," said Pierre Drossart, the other co-Principal
Investigator on VIRTIS. "What we want to understand is the overall 3D
thermal structure of the vortex, especially the vertical variation of the
horizontal winds."
The next step will be the correlation of this data and data collected in the
next sessions, with fluid dynamics computer models. This will eventually
help the scientists create the best possible atmospheric model of Venus to
date.
For more information
Giuseppe Piccioni
VIRTIS co-Principal Investigator, IASF-INAF, Rome, Italy
Email: Giuseppe.Piccioni @ iasf-roma.inaf.it
Pierre Drossart
VIRTIS co-Principal Investigator, Observatoire de Paris, France
Email: Pierre.Drossart @ obspm.fr
Han Svedhem
ESA Venus Express Project Scientist
Email: Hakan.Svedhem @ esa.int
[NOTE: Images and weblinks supporting this release are available at
http://www.esa.int/esaCP/SEMQKVU681F_index_1.html ]
http://www.esa.int
7 May 2007
Venus Express' infrared camera goes filming
An exciting new series of videos from ESA's Venus Express has been capturing
atmospheric details of day and night areas simultaneously, at different
altitudes.
The south pole of the planet and its gigantic double vortex has been
pictured as never before.
The south pole of Venus and the double-eyed storm permanently rule
atmospheric phenomena in that area of the planet. They are key to
understanding the global atmospheric dynamics on Venus and will contribute
to a better comprehension of the global meteorology of the planet.
In the search for all possible clues on how to solve the global atmospheric
'puzzle', the team of scientists behind the Ultraviolet, Visible and
Near-Infrared Mapping Spectrometer (VIRTIS) on board Venus Express, have
tried something new -- starting from the south pole.
They started by focusing on this target from the advantageous position of
the orbit apocentre (the furthest distance of the spacecraft from the
planet). This allows the instrument to keep the target in the field of view
for longer than in other portions of the orbit, where the spacecraft travels
faster. In this favourable position, scientists made efficient use of the
multi-wavelength capability of VIRTIS.
By using wavelengths longer than 3 microns in the thermal infrared range,
VIRTIS can obtain a combined view of the day and night sides simultaneously.
This is more convenient since at shorter wavelengths, the difference between
the thermal radiation emitted on the day and night sides is too high to
observe both regions simultaneously without 'blinding' some channels of the
camera.
"It is comparable to looking at bright, sun-illuminated snow and at a dark
sky without having to change your glasses," said Giuseppe Piccioni, VIRTIS
co-Principal Investigator. "In addition, within this observation process,
not only can we look at the dark and lit sides of the south pole at the same
time, but we can also look into the atmosphere at different depths. What we
are building is the most complete 3D data set of the Venusian atmosphere to
date."
The VIRTIS videos of the south polar vortex presented here are the result of
combined observations at two different wavelengths (3.8 and 1.7 microns,
respectively) used at the same time. The various images were taken over five
orbits, during a time-span of about 8 hours per orbit.
The 3.8-micron channel was chosen because of its compatibility (in exposure
time) with the 1.7-micron observations, as well as for its capability to
provide information about the cloud deck at about 65 kilometres altitude
over the planet. The 1.7-micron wavelength was chosen to probe the
atmosphere below the clouds when looking at the night side.
It is clearly possible to see that the morphology of the vortex changes a
lot during the 8-hour observation session and from one orbit to the next
(one Venus Express orbit is 24 hours long).
It is interesting to note that due to 'bad weather conditions', by the time
of the observations, the videos do not show the maximum achievable image
contrast. In fact, the visibility of the polar structure was somewhat
reduced by the local increase of the upper atmospheric haze.
"If the weather permits, by extending the time span of our future
observations, we may have the chance to obtain even clearer and more
detailed views of the polar vortex," added Piccioni.
"With video sequences of this kind, combining all the pieces of information
together, we can study the dynamics and the evolution of the vortex both in
the short and the long term," said Pierre Drossart, the other co-Principal
Investigator on VIRTIS. "What we want to understand is the overall 3D
thermal structure of the vortex, especially the vertical variation of the
horizontal winds."
The next step will be the correlation of this data and data collected in the
next sessions, with fluid dynamics computer models. This will eventually
help the scientists create the best possible atmospheric model of Venus to
date.
For more information
Giuseppe Piccioni
VIRTIS co-Principal Investigator, IASF-INAF, Rome, Italy
Email: Giuseppe.Piccioni @ iasf-roma.inaf.it
Pierre Drossart
VIRTIS co-Principal Investigator, Observatoire de Paris, France
Email: Pierre.Drossart @ obspm.fr
Han Svedhem
ESA Venus Express Project Scientist
Email: Hakan.Svedhem @ esa.int
[NOTE: Images and weblinks supporting this release are available at
http://www.esa.int/esaCP/SEMQKVU681F_index_1.html ]