The German geo-observations satellite CHAMP carries highly accurate vector instruments. The orientation of these relative to the inertial reference frame is obtained using star trackers. This Advanced Stellar Compass (ASC) is a fully autonomous unit, which provides, in real time, the absolute attitude with accuracy in the arc second range. In order to investigate the in-flight accuracy of the A...

Using the principle of energy conservation has been considered for gravity field determination from satellite observations since the early satellite era. CHAMP is the first satellite to which the energy balance approach can be usefully applied, now that near-continuous orbit tracking by GPS is available, aided by accelerometry. The feasibility of this approach has recently been demonstrated. Th...

In this paper we calculate explicitly the secular classical precessions of the node Ω and the perigee ω of an Earth artificial satellite induced by the static, even zonal harmonics of the geopotential up to degree l = 20. Subsequently, their systematic errors induced by the mismodelling in the even zonal geopotential coefficients Jl are compared to the general relativistic secular gravitomagnet...

Résumé : Nous présentons ici une métaphore de sculpture destinée au prototypage rapide de formes 3D. La surface sculptée correspond à l’iso-valeur d’un champ potentiel scalaire échantillonné spatiallement. L’utilisateur peut déposer de la matière où il le désire dans l’espace puis itérativement affiner sa forme grâce à un outil servant à déposer, retirer, peindre ou lisser de la matière, comme ...

We investigate the use of adaptative multigrid minimization algorithms for the estimation of the apparent motion eld. The proposed approach provides a coherent and eecient framework for estimating piecewise smooth ow elds for diierent parameterizations relative to adaptative partitions of the image. The performances of the resulting algorithms are demonstrated in the diicult context of a non co...

[1] The CHAMP satellite continues to provide highly accurate magnetic field measurements from decreasing orbital altitudes (<350 km) at solar minimum conditions. Using the latest 4 years (2004–2007) of readings from the CHAMP fluxgate magnetometer, including an improved scalar data product, we have estimated the lithospheric magnetic field to spherical harmonic degree 120, corresponding to 333 ...

The online bin packing problem is a well-known bin packing variant which requires immediate decisions to be made for the placement of a sequence of arriving items of various sizes one at a time into fixed capacity bins without any overflow. The overall goal is maximising the average bin fullness. We investigate a ‘policy matrix’ representation which assigns a score for each decision option inde...