Orbit determination of space objects based on sparse optical data

While building up a catalog of Earth orbiting objects, if the available optical observations are sparse, not deliberate follow ups of specific objects, no orbit determination is possible without previous correlation of observations obtained at different times. This correlation step is the most computationally intensive, and becomes more and more difficult as the number of objects to be discovered increases. In this paper we tested two different algorithms (and the related prototype software) recently developed to solve the correlation problem for objects in geostationary orbit (GEO), including the accurate orbit determination by full least squares solutions with all six orbital elements. Because of the presence in the GEO region of a significant subpopulation of high area to mass objects, strongly affected by non-gravitational perturbations, it was actually necessary to solve also for dynamical parameters describing these effects, that is to fit between 6 and 8 free parameters for each orbit. The validation was based upon a set of real data, acquired from the ESA Space Debris Telescope (ESASDT) at the Teide observatory (Canary Islands). We proved that it is possible to assemble a set of sparse observations into a set of objects with orbits, starting from a sparse time distribution of observations, which would be compatible with a survey capable of covering the region of interest in the sky just once per night. This could result in a significant reduction of the requirements for a future telescope network, with respect to what would have been required with the previously known algorithm for correlation and orbit determination.Comment: 20 pages, 8 figure

Light-time computations for the BepiColombo radioscience experiment

The radioscience experiment is one of the on board experiment of the Mercury ESA mission BepiColombo that will be launched in 2014. The goals of the experiment are to determine the gravity field of Mercury and its rotation state, to determine the orbit of Mercury, to constrain the possible theories of gravitation (for example by determining the post-Newtonian (PN) parameters), to provide the spacecraft position for geodesy experiments and to contribute to planetary ephemerides improvement. This is possible thanks to a new technology which allows to reach great accuracies in the observables range and range rate; it is well known that a similar level of accuracy requires studying a suitable model taking into account numerous relativistic effects. In this paper we deal with the modelling of the space-time coordinate transformations needed for the light-time computations and the numerical methods adopted to avoid rounding-off errors in such computations.Comment: 14 pages, 7 figures, corrected reference

ANKLE AND KNEE COORDINATION FOR SINGLE-LEGGED VERTICAL JUMPING COMPARED TO RUNNING

Similar basic movement patterns in ground reaction forces and ankle frontal plane kinematics of single-legged vertical jumping (JUMP) compared to running (RUN) have already been identified in earlier investigations. To broaden these findings, lower extremity kinematics of 25 subjects were recorded executing RUN and JUMP. Special focus was laid on the knee and ankle coordination of tibial endorotation and ankle eversion as well as on knee and ankle flexion/extension by applying a modified vector coding technique. RUN and JUMP demonstrated similar knee and ankle joint coordination patterns. However, differences in coupling angles unveiled phases, where joint coordination of ankle eversion/tibial endorotation was adjusted in JUMP. By comparing knee and ankle coordination of JUMP in healthy athletes with athletes suffering from anterior knee pain, common in sports with high jumping occurrences, key differences in execution leading to this overuse injury might be unveiled

STUD LENGTH AND STUD GEOMETRY OF SOCCER BOOTS INFLUENCE RUNNING PERFORMANCE ON THIRD GENERATION ARTIFICIAL TURF

The purpose of this study was to evaluate the influence of different stud lengths and stud geometries of soccer boots on soccer specific running performance. The study involved performance testing by running through two functional traction courses and corresponding subjective testing. Variables of this study were objectively measured running times and perception ratings of running performance. 15 experienced soccer players participated in the study. Players run slower when performing with shorter studs (

ELITE OUTSIDE HITTERS IN VOLLEYBALL DO NOT MEET THEIR INDIVIDUAL POSSIBLE MAXIMUM IMPACT HEIGHT IN HIGH SPIKE JUMPS

It is assumed that a high impact height is a relevant factor for success in volleyball spikes. The purpose of the study was to investigate whether outside hitters hit the ball at the highest possible impact height. Spikes from position IV were analysed at a tournament of the European League. The posture of the athletes was less extended in the trunk and upper limb with increasing jump height. Regarding the body posture at the moment of impact, there was no effect on the post impact ball speed. It is concluded that there could be enhancement with respect to the impact height as jump height increases even in elite athletes without reducing ball speed. This should be addressed within the training process

Low-frequency modes in the Raman spectrum of sp-sp2 nanostructured carbon

A novel form of amorphous carbon with sp-sp2 hybridization has been recently produced by supersonic cluster beam deposition showing the presence in the film of both polyynic and cumulenic species [L. Ravagnan et al. Phys. Rev. Lett. 98, 216103 (2007)]. Here we present a in situ Raman characterization of the low frequency vibrational region (400-800 cm-1) of sp-sp2 films at different temperatures. We report the presence of two peaks at 450 cm-1 and 720 cm-1. The lower frequency peak shows an evolution with the variation of the sp content and it can be attributed, with the support of density functional theory (DFT) simulations, to bending modes of sp linear structures. The peak at 720 cm-1 does not vary with the sp content and it can be attributed to a feature in the vibrational density of states activated by the disorder of the sp2 phase.Comment: 15 pages, 5 figures, 1 tabl

EVALUATION OF PLAYER-SURFACE INTERACTION ON ARTIFICIAL SOCCER TURF DURING CUTTING MOVEMENTS

The purpose of this study was to evaluate the traction characteristics of four different stud configurations on 2-Star, third generation artificial soccer turf during cutting movements. Traction, among others, characterizes player-surface interaction and is a key for top level performance in soccer. The concept of this study involves a combination of performance, subjective-sensory and biomechanical testing. Parameters of this study were: running times, subjective rankings and ratings and ground reaction forces. A subject pool of 26 soccer players was available for the study. The results show that subjects run slower, perceive worse, and evoke lower shear force values in soft ground design. It is concluded that a hard ground or partly a firm ground stud configuration is better suited than a soft ground stud configuration for playing on artificial turf. In this study, number, geometry and positioning of studs were the important aspects to achieve good and functional traction. With regard to methodological considerations, the combined approach consisting of three interdependent studies shows valuable and necessary insight of traction properties of different shoe-surface interfaces

VELOCITY AND ACCURACY AS PERFORMANCE CRITERIA FOR THREE DIFFERENT SOCCER KICKING TECHNIQUES

Kicking velocity (KV) and kicking accuracy (KA) of 19 experienced male soccer players were examined for the full instep, the inner instep, and the side foot kick. Measurements were performed simultaneously by a radar gun (KV) and a newly introduced high-speed-video camera set-up (KA). Subjects had two different tasks: to kick as fast as possible (Max KV) and to kick as accurate as possible (Max KA) with each kicking technique. Six repetitive kicks were performed for each required condition. The full instep and the inner instep kick were faster compared to the side foot kick for both performance tasks. In contrast, the side foot kick was the more accurate technique compared to the inner instep and the full instep kick, also for both performance tasks. Kicking variability between and within subjects was generally low for KV and generally high for KA for all kicking. It is concluded that velocity control is easier to achieve than accuracy control for soccer kicks

FRCM-to-masonry bonding behaviour in the case of curved surfaces: Experimental investigation

Fabric-reinforced cementitious matrix (FRCM) are composite materials more and more used for the reinforcement of masonry structures. The combination of high tensile strength fabrics (or meshes) with cementitious matrices, having good thixotropic capabilities and vapour permeability, makes such composites suitable for reinforcing a large number of masonry structures, including the one belonging to the historic heritage. FRCMs are bonded to the outer surfaces of structural masonry elements and, thanks to their adhesive capacity, bear much of the tensile stresses that unreinforced masonry cannot withstand. The effectiveness of such reinforcements, which is highly dependent on their ability to adhere to the masonry substrate, is generally investigated throughout specific experimental investigations (shear tests). Almost all the papers in the literature devoted to bond-slip analysis refer to the case of flat bonding surfaces, although these reinforcements are also widely used on curved structural elements such as arches and vaults. Therefore, this paper reports and examines the results of an extensive experimental program concerning the behavior of FRCM systems applied on curved masonry specimens. The results point out the influence of both curvature and reinforcement position (intrados or extrados) on the response of specimens in terms of bearing capacity, failure mode and post-peak response