Ground-based observatories join forces with Venus Express (Forwarded)

ESA News
http://www.esa.int

23 May 2007

Ground-based observatories join forces with Venus Express

Data from Venus Express, which has been revealing new and crucial details
about our closest planetary neighbour, will now be augmented by synoptic
data from a coordinated ground-based observation campaign.

This campaign will contribute to the growing body of information on the
nature of Venus's atmosphere and will help put the spacecraft's observations
into a broader context.

Between 23 May and 9 June, scientists working at a dozen telescopes and
observatories spread all over the world will examine Venus from the ground
and perform measurements, some of which are not feasible for Venus Express.

By applying different techniques and performing measurements at wavelengths
that are not within the capabilities of the spacecraft, scientists intend to
complement the existing dataset and obtain simultaneous measurements and
cross-validation of the spacecraft's observations.

Thus the ground-based observations -- radio, submillimetre, infrared and
visible -- are very useful for interpretation of Venus Express results.

The main focus of the ground-based observations is on measurements of the
atmosphere above Venus' cloud tops. This will complement Venus Express'
capability to study the cloud layer in high detail and the lower atmospheric
altitudes, down to the surface.

Spectroscopy at visible, infrared and submillimetre wavelengths from
ground-based observatories will enable direct measurements of the wind and
unearth fresh data about the mesosphere and the thermosphere, two
atmospheric layers situated above Venus' cloud deck.

This directly complements Venus Express, which determines wind
characteristics by tracking motions of the clouds and studies the
distribution of gaseous species and temperatures in Venus' upper atmosphere.

Following on Venus Express' investigations, the ground-based observations
will perform studies of Venus' oxygen airglow emission -- a phenomenon
detectable on the night-side that makes the planet glow -- and study the
composition of the mesosphere and the deep atmosphere.

The timeframe of the ground-based campaign, which extends from 23 May to 9
June, was chosen for different reasons. The most important reason is the
fact that Venus is close to its maximum elongation, that is its maximum
angular distance from the Sun as seen from Earth, during this period. This
is a favourable position for observations of both its day and night sides
from Earth.

The time window also encompasses the Venus flyby of NASA's Messenger on 6
June at 1:10 CEST [5 June 2310 UTC], en route to its final destination,
Mercury. For one day, Messenger's observations of Venus will also complement
those from Venus Express and ground.

The telescopes involved in the Venus ground-based observation campaign a

* CFHT: Canada-France-Hawaii Telescope, Hawaii
* OHP: Observatoire de Haute Provence, France
* VLT: Very large Telescope, Chile
* Observatoire du Pic du Midi, Telescope Bernard Lyot (TBL), France
* IRAM: Institut de Radio-Astronomie Millimetrique, Spain
* IRAM PdB: Institut de Radio-Astronomie Millimetrique: antennae at Plateau
de Bures, France
* JCMT: James Clerk Maxwell Telescope, Hawaii
* Nobeyama: Radio Observatory, Japan
* HHT: Heinrich Hertz Submillimeter Telescope Observatory, Arizona, USA
* Kitt Peak National Observatory, Arizona, USA
* IRTF: Infrared facility, Hawaii
* AAT: Anglo-Australian Telescope, Siding Spring Mountain in north-western
New South Wales, Australia
* Keck telescope (Hawaii)

Ground-based campaigns for previous missions

"Previous examples demonstrate the importance of connecting space-borne
observations with the synoptic coverage provided by continued ground-based
programmes," said Emmanuel Lellouch, Venus Express Supporting Investigator
and coordinator of the ground-based observation campaign.

One of the recent ground-based observation campaigns in support of a
scientific mission was conducted during the Huygens probe's descent and
landing on Titan on 14 January 2005. As Huygens parachuted to the surface of
Titan, a battery of radio and optical telescopes around the world were
watching and listening.

The observations brought in new information on the atmosphere and surface
properties of Saturn's largest moon. They also provided information about
the probe's drift in the winds and thus helped to reconstruct the descent
trajectory and the coordinates of the landing site.

Other supporting ground-based observations were successfully performed for
other scientific missions such as ESA's SMART-1 which flew to the Moon and
NASA's Deep Impact which flew to comet 9P/Tempel 1.

There are also a large number of amateur astronomers watching Venus
regularly, obtaining excellent images to complement data from observatories.
During the current campaign, Venus is particularly bright and thus easily
observable, even with small telescopes -- for amateurs' viewing pleasure.

For more information

Emmanuel Lellouch, VEX Supporting investigator, Observatoire de Paris,
France
Email: Emmanuel.Lellouch @ obspm.fr

Olivier Witasse, ESA Venus Express Deputy Project Scientist
Email: Olivier.Witasse @ esa.int

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