Pose and Shape Reconstruction of a Noncooperative Spacecraft Using Camera and Range Measurements

Recent interest in on-orbit proximity operations has pushed towards the development of autonomous GNC strategies. In this sense, optical navigation enables a wide variety of possibilities as it can provide information not only about the kinematic state but also about the shape of the observed object. Various mission architectures have been either tested in space or studied on Earth. The present study deals with on-orbit relative pose and shape estimation with the use of a monocular camera and a distance sensor. The goal is to develop a filter which estimates an observed satellite's relative position, velocity, attitude, and angular velocity, along with its shape, with the measurements obtained by a camera and a distance sensor mounted on board a chaser which is on a relative trajectory around the target. The filter's efficiency is proved with a simulation on a virtual target object. The results of the simulation, even though relevant to a simplified scenario, show that the estimation process is successful and can be considered a promising strategy for a correct and safe docking maneuver

Acute effects of caffeine and cigarette smoking on ventricular long-axis function in healthy subjects

<p>Abstract</p> <p>Background</p> <p>Few data exist regarding the direct effects of caffeine and smoking on cardiac function. We sought to explore the acute effects of caffeine assumption, cigarette smoking, or both on left ventricular (LV) and right ventricular (RV) function in a population of young normal subjects.</p> <p>Methods</p> <p>Forty-five healthy subjects aged 25 ± 2 years underwent echocardiography. Fifteen of them were non-smokers and habitual coffee consumers (group 1), 15 were smokers and not habitual coffee consumers (group 2), and 15 were smokers and habitual coffee consumers (group 3). Peak systolic (S_a), early diastolic E_a, and late diastolic (A_a) velocity of mitral annulus were measured by pulsed Tissue Doppler, and left atrioventricular plane displacement was determined by M-mode. Tricuspid annular velocities and systolic excursion (TAPSE) were also determined. Measurements were performed at baseline and after oral assumption of caffeine 100 mg in group 1, one cigarette smoking in group 2, and both in group 3.</p> <p>Results</p> <p>No changes in ventricular function were observed in group 1 after caffeine administration. In group 2, cigarette smoking yielded an acute increase in mitral A_a(+12.1%, p = 0.0026), tricuspid S_a(+9.8%, p = 0.012) and TAPSE (+7.9%, p = 0.017), and a decrease in the mitral E_a/A_aratio (-8.5%, p = 0.0084). Sequential caffeine assumption and cigarette smoking in group 3 was associated with an acute increase in mitral A_a(+13.0%, p = 0.015) and tricuspid A_a(+11.6%, p < 0.0001) and a reduction in mitral E_a/A_aratio (-8.5%, p = 0.0084) tricuspid E_a(-6.6%, p = 0.048) and tricuspid E_a/A_aratio (-9.6%, p = 0.0003). In a two-way ANOVA model controlling for hemodynamic confounding factors, changes in the overall population remained significant for mitral A_aand E_a/A_aratio, and for tricuspid A_aand E_a/A_aratio.</p> <p>Conclusion</p> <p>In young healthy subjects, one cigarette smoking is associated to an acute impairment in LV diastolic function and a hyperdynamic RV systolic response. Caffeine assumption alone does not exert any acute effect on ventricular long-axis function, but potentiates the negative effect of cigarette smoking by abolishing RV supernormal response and leading to a simultaneous impairment in both LV and RV diastolic function.</p

Bone sarcomas: ESMO–EURACAN–GENTURIS–ERN PaedCan Clinical Practice Guideline for diagnosis, treatment and follow-up

Production costs have been covered by ESMO from central funds

What is the role of the placebo effect for pain relief in neurorehabilitation? Clinical implications from the Italian consensus conference on pain in neurorehabilitation

Background: It is increasingly acknowledged that the outcomes of medical treatments are influenced by the context of the clinical encounter through the mechanisms of the placebo effect. The phenomenon of placebo analgesia might be exploited to maximize the efficacy of neurorehabilitation treatments. Since its intensity varies across neurological disorders, the Italian Consensus Conference on Pain in Neurorehabilitation (ICCP) summarized the studies on this field to provide guidance on its use. Methods: A review of the existing reviews and meta-analyses was performed to assess the magnitude of the placebo effect in disorders that may undergo neurorehabilitation treatment. The search was performed on Pubmed using placebo, pain, and the names of neurological disorders as keywords. Methodological quality was assessed using a pre-existing checklist. Data about the magnitude of the placebo effect were extracted from the included reviews and were commented in a narrative form. Results: 11 articles were included in this review. Placebo treatments showed weak effects in central neuropathic pain (pain reduction from 0.44 to 0.66 on a 0-10 scale) and moderate effects in postherpetic neuralgia (1.16), in diabetic peripheral neuropathy (1.45), and in pain associated to HIV (1.82). Moderate effects were also found on pain due to fibromyalgia and migraine; only weak short-term effects were found in complex regional pain syndrome. Confounding variables might have influenced these results. Clinical implications: These estimates should be interpreted with caution, but underscore that the placebo effect can be exploited in neurorehabilitation programs. It is not necessary to conceal its use from the patient. Knowledge of placebo mechanisms can be used to shape the doctor-patient relationship, to reduce the use of analgesic drugs and to train the patient to become an active agent of the therapy

Navigation system architecture in spacecraft swarms

Space mission require the implementation of a guidance, navigation and control (GNC) loop, either autonomous or built on remote assets, to correctly attain their goal. The increasing interest for mission architectures inspired by biological systems and based on a large number of elementary agents, typically labelled as swarms, introduces the issue of the identification of the most suitable GNC configuration. This paper explores the problem with specific reference to the navigation function, which is a pre-requisite to a suitable GNC. A simple, upper boundary for acceptable navigation performance in swarms is proposed, and this constraint is therefore considered in different possible exploration scenarios. The navigation options available in each scenario – either autonomous or based on external infrastructures - are then compared with respect to this condition

Relative navigation in autonomous spacecraft formations

Spreading of spacecraft formations and constellations made up by affordable platforms as cubesats poses the issue of technologically simple navigation subsystems, mandatory to exploit these missions. This paper describes solutions based on hardware that should be either already included or easy to accommodate on these platforms. Specifically, basic radiofrequency link's observables as the signal strength and the Doppler shift, and findings from onboard camera as a coarse positioning of the target are considered. The accuracy in the relative navigation attainable by means of simple estimation processes, easy to implement in the onboard computer, is obtained. The approach could also be used to identify inexpensive back-up solutions to more complex and accurate main navigation subsystems

Advantages and capabilities of an in-space navigation infrastructure in Moon and Mars missions

Future space activities are likely to include frequent missions toward Moon and Mars. The exploitation of these missions will require extensive navigation and guidance, and limited and expensive ground-based assets could be advantageously integrated or substituted by autonomous capabilities. The paper investigates two possible approaches to provide these capabilities by means of a navigation infrastructure. The first approach deals with exploiting at their limit the possibilities of the Global Navigation Satellite Systems (GNSSs) that, while primarily directed to serve the Earth and the low altitude orbits, are also able to extend their serviced volume at higher altitudes. By means of advanced use of the GNSS signals and a special architecture of the on-board navigation subsystem it would be possible to guide autonomously a complete mission to the Moon. The second approach is based on a local satellite-based navigation system devoted to a celestial body which is going to become the target of a number of missions. Such a kind of infrastructure, also able to provide data relay and communication services, could be of interest in the frame of an intense Mars exploration as a significant help in Martian operations. This system should be far simpler than current GNSS, providing the service to the areas of interest without a continuity requirement. A very quick reminder of alternative techniques that may have some role in the medium future – and therefore should be taken into account in the analysis of the problem - completes the paper

Efficient techniques for relative motion analysis between eccentric orbits under J2 effect

Accurate orbital propagation is required in order to correctly estimate (in design phase) and carry out (during operations) the control actions needed to maintain relative geometry among formation's spacecraft. Such an accurate propagation could be easily obtained by numerical methods, but their relevant computation cost would neither allow for general trade-offs during design nor match the onboard capabilities once spacecraft are in space. The interest for analytic, closed form solution is clear, as it would save on computation resources and allows for both speed and portability advantages. This paper proposes a special writing of the equations of motion which does provide a closed form solution for orbits including the oblateness effect. Such a representation is far more realistic than the approximate Keplerian one for LEO and medium altitude formations environment, and has indeed a remarkable appeal. The approach, originated from previous literature, is to express the variables of interest (radius, node, inclination, anomaly) as a series, which can be limited to the desired accuracy level in terms of eccentricity. The authors worked on this approach for several years, including currently available symbolic mathematics to allow for exact computation of the parameters of interest at every desired time. The more important contribution is a correct writing of the formulation in terms of relative dynamics, i.e. in terms of differences in the orbital parameters of the platforms, which is actually what is required in the spacecraft formation case. The paper details this special writing of the equation of motion and provides the analytical solution for eccentricities up to 0.2; i.e., remarkably extending the range of orbits previously considered in literature. These solutions are validated with respect to standard numerical propagators that end up with taking orders of magnitude longer to provide the same accuracy. Their quite high efficiency in terms of computational resources needed make them a suitable solution for inclusion in the onboard software, or a performing option for trade-off analysis during design phase

Communication and navigation architecture for planetary exploration carried-on by a swarm of mobile robots

Planetary exploration is a milestone of future space programs. Continuous evolution in robotics technologies, including improvement in sensors, in miniaturization, in software engineering allows to focus on the concept of unmanned, autonomous exploration carried on by swarm of mobile robots. As taught by several biology's examples, the cooperation among smaller, simpler agents provide effectiveness and ensures a good return even in case of the loss of some - or several - robots. This cooperation is primarily based on the exchange among the swarm's agents of information including payload data and positioning insight. A simple (to keep expandable platforms and their subsystems at a reasonable level in cost and complexity), yet effective communication and navigation architecture is requested to perform the task. The paper is part of a project aiming to first analyse the requirements for this architecture at the general level, and then investigate possible solutions by means of numerical simulations performed with purposely prepared software codes. Performance clearly depends on the mission environment, and in such a concern swarms composed by rovers, drones or low-altitude flying platforms have to be considered, include peculiar motion constraints and issues. Simulations consider radiofrequency links in different bands, with preliminary modelling of the channels' characteristics. Obstacles and outages, breaking the connections, are modelled. A specific attention is devoted to the navigation, in order to assess the nature and amount of data required to provide either a relative or absolute positioning capability: this information is crucial for referencing the data collected by the payload as well as for the coordinated guidance of the swarm. Being robustness the crucial asset of the swarm concept, the performance in different mission scenarios are evaluated on the basis of both deterministic and non-deterministic failures. Previous hands-on experience gained from studies and experiments devoted to small fleets of rovers operating in terrestrial, hostile environment is an important input for this research. As a result, a software code in MATLAB has been prepared and tested in order to be able, during next step of the project, to simulate in details the behaviour of fleets ranging from 2 to tens of agents operating in different scenarios of interest for planetary exploration. In this software code, the communications behaviour enters by limiting the mutual availability of information to the different agents (outages due to interposed obstacles) or out-of-range relative positioning. Navigation instead comes with the uncertainty in the knowledge of the kinematic state. These missing data affect the guidance computation and indeed limit the effectiveness of the exploration itself