The paper describes the Rosetta Lander named Philae and introduces its complement of scientific instruments. Philae was launched aboard the European Space Agency Rosetta spacecraft on 02 March 2004 ...and is expected to land and operate on the nucleus of 67P/Churyumov-Gerasimenko at a distance of about 3 AU from the Sun. Its overall mass is ~98 kg (plus the support systems remaining on the Orbiter), including its scientific payload of ~27 kg. It will operate autonomously, using the Rosetta Orbiter as a communication relay to Earth. The scientific goals of its experiments focus on elemental, isotopic, molecular and mineralogical composition of the cometary material, the characterization of physical properties of the surface and subsurface material, the large-scale structure and the magnetic and plasma environment of the nucleus. In particular, surface and sub-surface samples will be acquired and sequentially analyzed by a suite of instruments. Measurements will be performed primarily during descent and along the first five days following touch-down. Philae is designed to also operate on a long time-scale, to monitor the evolution of the nucleus properties. Philae is a very integrated project at system, science and management levels, provided by an international consortium. The Philae experiments have the potential of providing unique scientific outcomes, complementing by in situ ground truth the Rosetta Orbiter investigations.
The outcome of the first stage of planetary formation, which is characterized by ballistic agglomeration of preplanetary dust grains due to Brownian motion in the free molecular flow regime of the ...solar nebula, is still somewhat speculative. We performed a microgravity experiment flown onboard the space shuttle in which we simulated, for the first time, the onset of free preplanetary dust accumulation and revealed the structures and growth rates of the first dust agglomerates in the young solar system. We find that a thermally aggregating swarm of dust particles evolves very rapidly and forms unexpected open-structured agglomerates.
The energy lattice sum rule for the static quark–antiquark potential is checked using lattice perturbation theory up to next-to-leading order. To this end, the expectation value of the sum over the ...spatial plaquettes is computed. The various contributions to the quark–antiquark potential in the quenched approximation are analyzed.
The phase selection process during the crystallization of undercooled metallic melts is studied in situ by combining the electromagnetic levitation technique with energy dispersive x-ray diffraction ...of synchrotron radiation. The crystallization of metastable bcc phase in binary Ni-V alloys was identified. A metastable phase diagram of Ni-V alloy is constructed, which shows the primarily solidifying phase as a function of composition and undercooling. The analysis within nucleation theory emphasizes the important role of metal oxide as a heterogeneous nucleation site controlling the phase selection.
Almost 50 years after the launch of Sputnik, the diversity and criticality of the technology and applications already in place to exploit the 'high-frontier' is impressive. And it is no exaggeration ...to state that a precondition for meeting human needs, coping with environmental problems, and maintaining security is the successful exploitation of space. Yet no one overview exists to document what we have so far done, and soon plan to accomplish, to utilize the near-Earth space environment. Utilization of Space aims to serve as an authoritative overview for professionals and interested laymen by explaining scientific space utilisation, commercial and entrepreneurial issues, and technological applications. The chapters are written by leading specialists in the respective fields and on a level comprehensible to an educated, but not necessarily technically-trained, reader. Enhanced by informative color illustrations, it is intended not only to transmit useful and timely information to readers, but also to share with them the fascination attached to space activities experienced by those actively engaged in them.
“Rosetta” is a Cornerstone Mission of the Horizon 2000 ESA Programme. Its goal is to rendezvous with a comet and to study its nucleus and coma using an orbiting spacecraft and a landed platform. The ...latter is called Philae; the Rosetta Lander has been designed to land softly on the comet nucleus and is equipped with 10 scientific instruments to perform in situ studies of cometary material.
The Lander system is provided by international consortium with the participation of Germany, France, Italy, United Kingdom, Finland, Ireland, Hungary and Austria.
The original Rosetta mission was planned to launch in January 2003 to reach comet 47P/Wirtanen in 2011 at a heliocentric distance of about 3
AU. Due to uncertainties regarding the reliability of the Ariane 5 launcher (after a catastrophic failure in December 2002) the Rosetta launch was postponed and a new mission studied.
Changed mission characteristics (e.g. in launcher capacity; no swing-by at Venus) strongly limited the number of possible alternatives. After careful investigation, a decision was taken for a mission to comet 67/P Churyumov-Gerasimenko with a launch date in February 2004 and rendezvous in 2014.
This new mission scenario has significant consequences for the Rosetta Lander, because the nucleus of P/Churyumov-Gerasimenko is expected to be considerably larger than that of P/Wirtanen. Current best estimates assume a radius of about 2.0
km and, thus, a mass which is about two orders of magnitude larger than that of the original target comet. This impacts strongly on the Lander separation, descent and landing scenario. Analysis of the increased landing risk on P/Churyumov-Gerasimenko has led to modifications of the landing gear to cope with the increased impact velocities expected.
Two different diagrammatic construction schemes for obtaining the propagator for inelastic electronic scattering are presented. Both are discussed for the three cases that the target molecule of ...interest is closed-shell itself or has a closed-shell anion or cation. The 'direct approach' yields the inelastic propagator directly, but has the drawback that it requires the evaluation of a large number of diagrams already in low orders. The 'Dyson approach' uses Dyson-type equations for the inelastic propagator and employs a diagrammatic construction scheme for the generalized one-particle densities only. It therefore requires a considerably lower number of diagrams. Results are given up to first order for both methods and all three cases. Alternative approaches are briefly discussed and compared with our methods.
Containerless undercooling in an electromagnetic levitation device was used to observe solidification velocities as a function of undercooling temperature for pure Ni and Cu-Ni alloys. In a limited ...temperature range, the results can be interpreted using current theories, provided the conditions for local equilibrium at the solid-liquid interface are relaxed. Beyond a certain undercooling value, the observations differ markedly from current predictions. (Author)
A numerical model is developed describing the very fast process of microstructure evolution under the common action of nucleation and diffusional growth of minority phase droplets during cooling of a ...hypermonotectic alloy through the miscibility gap. The model is validated comparing it with an analytical solution obtained with some simplifying assumptions and then applied to predict the microstructure evolution in Al-Pb alloy in a real casting situation. The numerical model reflects the real physical processes well and also yields some general relations applicable to other immiscible alloys.
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