[Baps] BU seminar Thurs. 10 July, 3pm, by J-L Bertaux

[Paul Withers]

Directions, etc, at:
http://www.bu.edu/dbin/csp/?q=CSP_sem

Results from Venus Express SPICAV/SOIR instrument.

Paul

-------- Original Message --------
Subject: [Announce] special seminar Thurs. 10 July
Date: Mon, 7 Jul 2008 14:45:07 -0400 (EDT)
From: John T. Clarke <jclarke at soleil.bu.edu>
To: announce at bu-ast.bu.edu
CC: John T. Clarke <jclarke at soleil.bu.edu>

Dear all,

    There will be a special seminar on Thurs. by our colleague Dr.
Jean-Loup Bertaux, who will be visiting BU later in the week:

   Latest news from Venus

   Jean-Loup Bertaux
   Service d'Aeronomie du CNRS
   France

   Thurs. 10 July 2008
   CAS Rm. 500

I will present some results of the Venus Express ESA mission, presently in
orbit around Venus.  The main emphasis will be on the results obtained
with the SPICAV/SOIR instrument, an ensemble of three spectrometers.
A UV spectrometer (118 - 320 nm, resolution 1.5 nm) is identical to the
MEX version. It is dedicated to nadir viewing, limb viewing and vertical
profiling by stellar and solar occultation. In nadir orientation, SPICAV
UV analyzes the albedo spectrum (solar light scattered back from the
clouds) to retrieve SO2, and the distribution of the UV-blue absorber (of
still unknown origin) on the day side with implications for cloud
structure, and atmospheric dynamics. On the night side, ^ and  bands of NO
are monitored: this emission, highly variable,  is produced when O and N
atoms, produced by photo-dissociation of CO2 and N2 on the day side,  are
recombining when air is descending on the night side. A similar O2
emission at 1.27 microns is simultaneously recorded by the VIRTIS
instrument. There seems to be no correlation between the two
emissions, a serious constraint on upper atmosphere circulation. In the
stellar occultation mode the UV sensor measures the vertical profiles of
CO2, temperature, SO2, and aerosols clouds. A warm layer around 100-120 km
was discovered, believed to be due to adiabatic heating of air descent.
In solar occultation mode, SO2 is seen up to 100 km, a puzzling result
since it should be photo-dissociated at this altitude.  The SPICAV
VIS-IR sensor (0.7-1.7 micron, resolution 0.5-1.2 nm) employs a
pioneering technology: acousto-optical tunable filter (AOTF). It monitors
H2O on the day side, and analyzes the aerosol spectral behavior in solar
occultation.  The SOIR spectrometer is a new Solar Occultation IR
spectrometer in the range=2.2-4.3 microns, with a spectral resolution
/>15,000, the highest on any solar system mission. This new concept
includes a combination of an echelle grating and an AOTF crystal to sort
out one order at a time. SOIR is yielding HDO, H2O, HCl, HF, CO,
vertical profiles, as well as aerosols. A new band of CO16O18 isotope was
discovered in the atmosphere of Venus, simultaneously with its discovery
on Mars by Villanueva et al (2007).  During solar occultation the 3
spectrometers are activated; the study of aerosol absorption from 0.2 to 4
micron shows that the size distribution of aerosols must be bi-modal.
Some results of other instruments VIRTIS, MAG, ASPERA, and VERA (radio
occultation) will also reported.


-- 
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Paul Withers                            Center for Space Physics
Office  +1 617 353 1531                 Boston University
Fax     +1 617 353 6463                 725 Commonwealth Avenue
Email   withers at bu.edu                  Boston MA 02215, USA
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