Thermal structure in the Venus middle cloud layer

Thermal structure measurements obtained by the two Vega balloons show the Venus atmosphere in the middle cloud layer to be near-adiabatic, on the whole; but discrete air masses are present that differ slightly from one another in potential temperature and entropy. The Vega 1 temperatures are 6.5 K warmer than measured by Vega 2 at given pressures. Measurements taken by the Vega 2 lander on descent through these levels agree with the Vega 2 balloon data

Meteorological Data Along the VEGA-1 and VEGA-2 Float Paths

During their flight through the Venus atmosphere the Vega 1 and Vega 2 balloon craft measured the pressure and temperature of the ambient medium, the vertical wind-velocity component (relative to the gondola), the cloud-layer backscatter coefficient, the mean illumination level, and the number and time of possible lightning flashes. In addition, the ground radio telescope network measured the balloon positions and drift velocities by the differential VLBI technique; these data are now being processed

Compression d'images pour la mission d'exploration planetaire phobos II

L'étude réalisée pour la mission internationale d'exploration planétaire Phobos II dans le cadre d'une coopération franco-soviétique concerne la compression à bord de la sonde d'atterrissage, des images acquises sur Phobos, avant la transmission vers la Terre. La méthode de compression développée utilise la Transformation Cosinus Discrète appliquée sur des blocs de taille 16 x 16. Un seuillage adaptatif est effectué pour le choix des coefficients à garder. Les coefficients sont quantifiés uniformément et codés par des mots binaires de longueur fixe. L'emplacement des coefficients conservés est représenté par quadtree. Les résultats de simulation sont concluants. Les premières images seront reçues et décodées à partir d'avril 1989

The NetLander atmospheric instrument system (ATMIS): Description and performance assessment

The pointwise meteorological observations of the Viking Lander and Mars Pathfinder as well as the orbital mapping and sounding performed by, e.g., Mariner 9, Viking Orbiters and the Mars Global Surveyor have given a good understanding of the basic behaviour of the Martian atmosphere. However, the more detailed characterisation of the Martian circulation patterns, boundary layer phenomena and climatological cycles requires deployment of meteorological surface networks. The European NetLander concept comprising four well-instrumented landers is being studied for launch in 2005 and operations spanning at least a Martian year in 2006-2008. The landers are to be deployed to areas in both Martian hemispheres from equatorial regions to low mid-latitudes. The NetLander atmospheric instrument system (ATMIS) on board each of the landers is designed to measure atmospheric vertical profiles of density, pressure and temperature during the descent onto the surface, as well as pressure, atmospheric and ground temperatures, wind, atmospheric optical thickness and humidity through a full Martian year, possibly beyond. The main operational objective of this meteorological experiment is to provide a regular time series of the meteorological parameters as well as accelerated measurement campaigns. Such a data set would substantially improve our understanding of the atmospheric structure, dynamics, climatological cycles, and the atmosphere-surface interactions. The ATMIS sensor systems and measurement approaches described here are based on solutions and technologies tested for similar observations on Mars-96, Mars Pathfinder, Huygens, and Mars Polar Lander. Although the number of observation sites only permits characterisation of some components of the general circulation, the NetLander ATMIS will more than double the number of in situ vertical profiles (only three profiles - two from Viking Landers and one from Mars Pathfinder - are currently available and as envisioned at the time of writing, none of the 2001 and 2003 landers' payloads include entry phase measurements of pressure or temperature), perform the first in situ meteorological observations in the southern low- and mid-latitudes and provide the first simultaneous in situ multi-site observations of the local and general circulation patterns, in a variety of locations and terrains. As such, NetLander ATMIS will be the precursor of more comprehensive meteorological surface networks for future Mars exploration. © 2000 Elsevier Science Ltd. All rights reserved

DYNAMO: a Mars upper atmosphere package for investigating solar wind interaction and escape processes, and mapping Martian fields

DYNAMO is a small multi-instrument payload aimed at characterizing current atmospheric escape, which is still poorly constrained, and improving gravity and magnetic field representations, in order to better understand the magnetic, geologic and thermal history of Mars. The internal structure and evolution of Mars is thought to have influenced climate evolution. The collapse of the primitive magnetosphere early in Mars history could have enhanced atmospheric escape and favored transition to the present arid climate. These objectives are achieved by using a low periapsis orbit. DYNAMO has been proposed in response to the AO released in February 2002 for instruments to be flown as a complementary payload onboard the CNES Orbiter to Mars (MO-07), foreseen to be launched in 2007 in the framework of the French PREMIER Mars exploration program. MO-07 orbital phase 2b (with an elliptical orbit of periapsis 170 km), and in a lesser extent 2a, offers an unprecedented opportunity to investigate by in situ probing the chemical and dynamical properties of the deep ionosphere, thermosphere, and the interaction between the atmosphere and the solar wind, and therefore the present atmospheric escape rate. Ultraviolet remote sensing is an essential complement to characterize high, tenuous, layers of the atmosphere. One Martian year of operation, with about 5,000 low passes, should allow DYNAMO to map in great detail the residual magnetic field, together with the gravity field. Additional data on the internal structure will be obtained by mapping the electric conductivity, sinergistically with the NETLANDER magnetic data. Three options have been recommended by the International Science and Technical Review Board (ISTRB), who met on July 1st and 2nd, 2002. One of them is centered on DYNAMO. The final choice, which should be made before the end of 2002, will depend on available funding resources at CNES