European Space Operations Centre

About: European Space Operations Centre is a government organization based out in Darmstadt, Germany. It is known for research contribution in the topics: Orbit determination & Satellite. The organization has 309 authors who have published 331 publications receiving 10399 citations. The organization is also known as: ESOC.

From laboratory experiments to LISA Pathfinder: achieving LISA geodesic motion

Abstract: This paper presents a quantitative assessment of the performance of the upcoming LISA Pathfinder geodesic explorer mission. The findings are based on the results of extensive ground testing and simulation campaigns using flight hardware, flight control and operations algorithms. The results show that, for the central experiment of measuring the stray differential acceleration between the LISA test masses, LISA Pathfinder will be able to verify the overall acceleration noise to within a factor 2 of the LISA requirement at 1 mHz and within a factor 6 at 0.1 mHz. We also discuss the key elements of the physical model of disturbances, coming from LISA Pathfinder and ground measurement that will guarantee the LISA performance.

An innovative product for space mission planning an a posteriori evaluation

Abstract: This paper describes MEXAR2, a software tool that is currently used to synthesize the operational commands for data downlink from the on-board memory of an interplanetary space mission spacecraft to the ground stations. The tool has been in daily use by the Mission Planning Team of MARS EXPRESS at the European Space Agency since early 2005. Goal of this paper is to present a quick overview of how the planning and scheduling problem has been addressed, a complete application customized and put into context in the application environment. Then it concentrates on describing more in detail how a core solver has been enriched to create a tool that easily allows users to generate diversified plans for the same problem by handling a set of control parameters, called heuristic modifiers, that insert heuristic bias on the generated solutions. A set of experiments is presented that describes how such modifiers affect the solving process.

Interstellar dust flux measurements by the Galileo dust instrument between the orbits of Venus and Mars

Abstract: [i] We present an analysis of the data obtained by the Galileo in situ dust instrument for interstellar dust (ISD). Between December 1989 and the end of 1993, three orbit segments were favorable for the detection of ISD at less than 3 AU heliocentric distance. After removing background events from the data sample, which were mostly due to interplanetary dust impactors, we infer that the flux of ISD grains between 0.7 AU and 3 AU is about 4 x 10 -5 m -2 s -1 . This result is compatible with the ISD flux of 3 × 10 -5 m -2 s -1 (grain size 0.4 μm) derived from the Cassini measurements at about 1 AU. Using a new concept called ISD β spectroscopy, we are able to estimate at different locations in the inner solar system the ISD flux alteration resulting from the competing effects of radiation pressure and gravitation. In particular, we confirm results of previous Ulysses dust data analysis showing that radiation pressure prevents smaller ISD grains (radius smaller than 0.3 μm) from reaching the innermost region of the solar system. Furthermore, our analysis shows the relevance of gravitational focusing in the dynamics of bigger ISD grains (micron-sized grains). The Galileo measurements were performed 10 years before the Cassini measurements. Thus the available ISD data now cover almost a full 11-year solar cycle. Nonetheless, the flux of ISD grains with radius bigger than 0.4 μm shows no significant temporal variation. This suggests that the dynamics of these ISD grains is not influenced much by the interaction with the time-dependent solar magnetic field.

Aspect angle for interstellar magnetic field in SN 1006

Abstract: A number of important processes taking place around strong shocks in supernova remnants (SNRs) depend on the shock obliquity. The measured synchrotron flux is a function of the aspect angle between interstellar magnetic field (ISMF) and the line of sight. Thus, a model of non-thermal emission from SNRs should account for the orientation of the ambient magnetic field. We develop a new method for the estimation of the aspect angle, based on the comparison between observed and synthesized radio maps of SNRs, making different assumptions about the dependence of electron injection efficiency on the shock obliquity. The method uses the azimuthal profile of radio surface brightness as a probe for orientation of ambient magnetic field because it is almost insensitive to the downstream distribution of magnetic field and emitting electrons. We apply our method to a new radio image of SN 1006 produced on the basis of archival Very Large Array and Parkes data. The image recovers emission from all spatial structures with angular scales from a few arcsec to 15 arcmin. We explore different models of injection efficiency and find the following best-fitting values for the aspect angle of SN 1006: Φ o = 70° ± 4.2° if the injection is isotropic, Φ o = 64° ± 2.8° for quasi-perpendicular injection (SNR has an equatorial belt in both cases) and Φ o = 11° ± 0.8° for quasi-parallel injection (polar-cap model of SNR). In the last case, SN 1006 is expected to have a centrally peaked morphology contrary to what is observed. Therefore, our analysis provides some indication against the quasi-parallel injection model.