[show abstract][hide abstract] ABSTRACT: Venus has thick clouds of H2SO4 aerosol particles extending from altitudes of 40 to 60 km. The 60-100 km region (the mesosphere) is a transition region between the 4 day retrograde superrotation at the top of the thick clouds and the solar-antisolar circulation in the thermosphere (above 100 km), which has upwelling over the subsolar point and transport to the nightside. The mesosphere has a light haze of variable optical thickness, with CO, SO2, HCl, HF, H2O and HDO as the most important minor gaseous constituents, but the vertical distribution of the haze and molecules is poorly known because previous descent probes began their measurements at or below 60 km. Here we report the detection of an extensive layer of warm air at altitudes 90-120 km on the night side that we interpret as the result of adiabatic heating during air subsidence. Such a strong temperature inversion was not expected, because the night side of Venus was otherwise so cold that it was named the 'cryosphere' above 100 km. We also measured the mesospheric distributions of HF, HCl, H2O and HDO. HCl is less abundant than reported 40 years ago. HDO/H2O is enhanced by a factor of approximately 2.5 with respect to the lower atmosphere, and there is a general depletion of H2O around 80-90 km for which we have no explanation.
[show abstract][hide abstract] ABSTRACT: A new compact spaceborne high-resolution spectrometer developed for the European Space Agency's Venus Express spacecraft is described. It operates in the IR wavelength range of 2.2 to 4.3 microm and measures absorption spectra of minor constituents in the Venusian atmosphere. It uses a novel echelle grating with a groove density of 4 lines/mm in a Littrow configuration in combination with an IR acousto-optic tunable filter for order sorting and an actively cooled HgCdTe focal plane array of 256 by 320 pixels. It is designed to obtain an instrument line profile of 0.2 cm(-1). First results on optical and spectral properties are reported.
[show abstract][hide abstract] ABSTRACT: The acousto-optic spectrometer of the near infrared range, which is a part of the spectrometer SPICAM onboard the Mars-Express spacecraft, began to operate in the orbit of Mars in January 2004. In the SPICAM experiment, a spectrometer on the basis
of an acousto-optic filter was used for the first time to investigate other planets. During one and a half years of operation,
the IR channel of SPICAM obtained more than half a million spectra in the 1–1.7 μm range with a resolving power of more than
1500 in different modes of observation: limb, nadir, and solar eclipses. The main goal of the experiment is to study the content
of water vapor in the Martian atmosphere by measuring the absorption spectrum in the 1.38 μm band. Characteristics of the
instrument (high spectral resolution and signal-to-noise ratio) allow one to solve a number of additional scientific problems
including the study of ozone distribution by emission of singlet oxygen (O2
1Δg), detection of the water and carbonic dioxide ices, and also the study of the vertical distribution and optical characteristics
of aerosol in the Martian atmosphere. We present a description of the instrument, the results of its ground and in-flight
calibrations, and a brief survey of the basic scientific results obtained by the SPICAM spectrometer during a year-and-half
Cosmic Research 01/2006; 44(4):278-293. · 0.24 Impact Factor
[show abstract][hide abstract] ABSTRACT: [ 1] The SPICAM IR spectrometer on Mars Express mission (1.0 - 1.7 mu m, spectral resolution 0.5 - 1.2 nm) is dedicated primarily to nadir measurements of H(2)O abundance. It is one of two channels of SPICAM UV-IR instrument. In this spectrometer we applied for the first time in planetary research the technology of an acousto-optic tunable filter (AOTF) that allowed unprecedented mass reduction for such an instrument: 0.75 kg. SPICAM IR is a point nadir-looking spectrometer with sequential scanning of the spectrum by the AOTF. Sun occultations are performed with a help of dedicated solar port. We describe instrumentation, calibrations, and the modes of operations of the device and discuss its in-flight performances. A brief overview of the scientific measurements includes water vapor measurements and the mapping of intensity of the O(2)( a (1)Delta(g)) emission at 1.27 mu m, described in detail in separate papers. Measurements in reflected solar light allow clear detection of H(2)O and CO(2) ices on the surface or in the atmosphere of Mars. We discuss solar occultation measurements by SPICAM and present resulting vertical profiles of aerosol optical depth.
Planetary and Space Science 01/2006; 111(E9). · 2.11 Impact Factor
[show abstract][hide abstract] ABSTRACT: A short description is given of the Occultation Radiometer which has been flown recently on the EURECA carrier. A brief outline of the scientific rationale, instrument characteristics and status of the data reduction is presented.
Advances in Space Research 01/1995; 16(8):33-36. · 1.18 Impact Factor
[show abstract][hide abstract] ABSTRACT: Measurements of the deuterium-to-hydrogen ratios (D/H) in the fields of meteorology1,2, tropospheric3,4 and stratospheric chemistry5,6, planetology7,8 and cosmogony8,9 have previously been performed on molecules in which one hydrogen atom is replaced by one deuterium atom. We report here the first detection of isolated deuterium atoms in the Earth's upper atmosphere through their resonantly scattered Lyman-α emission. An atmospheric deuterium emission of 330 R (1 R=106 photons cm−2 s−1) is observed for a tangent altitude of 110 km during Spacelab 1 mission launched on 28 November 1983. The (D/H) ratio of 3×10−4 is slightly enriched over the seawater value of 1.6×10−4.