A Tutorial on the Tracking, Telemetry, and Command (TT&C) for Space Missions

This paper presents a tutorial on the Tracking, Telemetry, and Command (TT&C) for spacecraft and satellite missions. In particular, it provides a thorough summary of the design of the TT&C, starting from elementary system aspects and going down to the details of the on-board TT&C subsystem design, its units, and the physical layer. The paper is then complemented with a description of emerging TT&C techniques and technologies, the standardization framework, and practical examples of actual spacecraft design of European space missions. The here-presented tutorial is thought for professionals (also in other telecommunication engineering fields) willing to face the challenges and state-of-the-art of the TT&C, and know more about this fundamental function that allows us to control and monitor our spacecraft on a daily basis

On the use of Pseudo-Noise Ranging with high-rate spectrally-efficient modulations

In this paper, we study the feasibility of coupling the PN ranging with filtered high-order modulations, and investigate the simultaneous demodulation of a high-rate telemetry stream while tracking the PN ranging sequence. Accordingly, we design a receiver scheme that is able to perform a parallel cancellation, in closedloop, of the ranging and the telemetry signal reciprocally. From our analysis, we find that the non-constant envelope property of the modulation causes an additional jitter on the PN ranging timing estimation that, on the other hand, can be limited by properly sizing the receiver loop bandwidth. Our study proves that the use of filtered high-order modulations combined with PN ranging outperforms the state-of-the-art in terms of spectral efficiency and achievable data rate, while having comparable ranging performanc

Human Body Posturizer (H.B.P.): new orthosis for improving postural dynamics

Introduction. Posture is the result of many complex processes involving the entire body in relationship with different environmental changes (Penha P.J.,2005). Interaction between the different anatomical districts occurs at different levels and it is influenced by different initial conditions. Alterations in imbalances and associated diseases produce a structural and physiologic reorganization of the anatomical structures to improve postural dynamics (Kasim et al., 2010). Generally, these modifications can be divided into para-mophisms and dis-morphisms of the spine. Currently postural diseases are treated by passive (brace and orthosis) and active (gymnastic) methods according with the severity of imbalance (LeBauer et al., 2008; Ugwonali et al., 2004). Purpose of this study is to validate a new type of orthosis named Human Body Posturizer (H.B.P). It is a modular flexible structure composed of different modules which act on the cervical, thoracic and lumbar traits of the back, and an inferior module which acts on the inferior limbs. Materials and methods. The present study considers a sample of 20 male subjects with age spanning from 19 to 35 years (mean age 23,4 ± 4,3). Subjects underwent 4 weeks of H.B.P. treatment consisting of 30 minutes, two times for week. The sample was analyzed by using the Surfacer System (Diagnostic Support), which permits to capture the external geometry of the back. Each subject was sampled before and after the treatment and differences between pre and post treatment were analyzed trough geometric morphometric approach (Slice 2000). Results. The results of this study showed a reorganization of the bilateral structures of the back after treatment. In particular an increased degree of symmetry was observed both in trunk and lumbar regions of the back. Conclusions. The preliminary results of the present study suggest that the HBP, acts on the spatial organization of the back, rectifying the position of the anatomical components associated to the early postural diseases. Nevertheless these results should be considered as preliminary and need of further researches

Geometric morphometric approach in the study of the footprint variation in children between 6 and 12 years of age

Introduction. Footprint evaluation is a widely used method for determination of foot morphology. Generally, variation in footprint have been associated to vertical variation of the plantar vault, with particular attention to the middle longitudinal arch (MLA). In the children, MLA tends to be lower and accentuates naturally when approaching adolescence (Forriol and Pascual, 1990). Thought this condition is mostly asymptomatic, permanence of lower MLA after development is associated to flatfoot. In this study the morphology of the baropodometrical footprint was analysed by using geometric morphometric approach (Slice, 2000). This method permits to quantify the geometrical look of the anatomical structures by mean of coordinate system method. Material and methods. The footprints of 50 children with age spanning from 6 to 12 years were sampled using an electronic baropodometry. The external profile of the footprints were reduced to 50 equally spaced landmarks and superimposed using the Procrustes superimposition method. A principal component analysis was performed to evaluate the morphological variability of the footprints and sex and age difference were observed. Results. geometric morphometric results show that principal variations are localized in the medial region of the isthmus and are associated to a narrowing/widening of the footprint. No sex and age differences were observed, a part from a small group with age spanning from 6 to 9 years, showing a wider footprint. Conclusions. It is thought that principal modification of the MLA occurs in the pre-school years (Stavlas et al, 2005). The results of this analysis show an high variability of the footprint geometry, suggesting that ongoing development of the foot structure takes place also during school ages. Although these results are preliminary, they should carefully considered in the treatment of the flatfoot in children, considering that the development of the foot proceeds also after 6 year

An angio-tomographic approach to the study of the variation of the middle meningeal artery in humans

Introduction. The middle meningeal artery usually enters the endocranial cavity through the foramen spinosum, running within the dura mater and developing a vascular network on the frontal, parietal, and occipital surfaces of the brain. Little information is available on its morphogenesis and variation in human populations or within primates (Falk 1993). Its imprints on the endocranial walls can be recognised on fossil specimens, allowing inferences on the evolution of this vascular system. While extinct human species display a limited reticulation of this vessels, Homo sapiens shows a definite increase of its complexity (Bruner et al., 2005). Current hypotheses on the evolution of a complex meningeal vascularisation in our species include biomechanical protection and thermoregulation of the brain surface (Bruner et al., 2011). Taking into account the limited knowledge on the variation of this arterial network, this study is aimed at quantifying individual differences in the branching patterns, as well as at investigating the spatial relationships between middle meningeal arteries, cerebral arteries, and neurocranial bones. Methods. Angio-tomography and digital anatomy are used to reconstruct in vivo the meningeal vascular system in 37 individuals with age spanning from 20 to 85 years. Three-dimensional reconstructions of the cerebral and meningeal vascular systems have been computed by using Mimics 11.1 (Materialise Software). Variations in basic branching patterns have been described by standard anatomical approaches, as well as by using standard morphometrics. Complexity of the branching pattern has been quantified also by using fractal approaches (Zamir 1999). Results. Anatomical descriptions and metrics are reported for different age classes, sexes, and hemispheres, providing mean values and ranges of distribution accounting for the vascular patterns. Conclusions. Although the middle meningeal network shows a variable and complex geometry, its spatial organization can be quantified in terms of branching patterns and topological relationships with the neurocranial elements. This information allows to test evolutionary hypothesis by quantifying individual or between-groups differences. At the same time this information is helpful in biomedical and neurosurgical context, providing statistical values for the position and distribution of the vessels

RNN BCJR: a fully trainable version of the additive BCJR algorithm

We present a new version of the additive BCJR algorithm based on a recurrent neural network whose structure reflects an underlying trellis diagram. Starting from a matrix version of the equations of the additive BCJR algorithm, we derive the equivalent trainable recurrent neural network model, named Recurrent Neural Network (RNN) BCJR. The RNN BCJR consists of a linear layer to form the edge metrics from the state and input metrics, followed by a SOFTMAX/max* layer to marginalize the edge metrics back to the state and output spaces. We derive the recursions for delta propagation to train the two-layer mixing matrices from the output cost function. Unlike the previous approaches, the proposed RNN BCJR can completely replace the BCJR and is trainable from the cost functions of the outputs. The trained RNN BCJR achieves the same optimal performance as the BCJR when the model is known but at the same time can adapt itself to model mismatch, thus outperforming BCJR

On the use of PN Ranging with High-rate Spectrally-efficient Modulations in Satellite Payload Telemetry Links

Pseudo Noise (PN) ranging is a ranging technique that has been recently introduced in near-Earth space research (SR) missions. For these, at the state-of-the-art, the PN ranging signal is combined with a high-rate telemetry stream binary modulated in phase. The coupling of the two, together with the 10 MHz bandwidth constraint imposed for this class of missions, translates into a data rate bound of approximately 10 Mbps. The purpose of this article is to prove the feasibility of overcoming the current data rate limitation by defining a communication architecture that foresees the coupling of the PN ranging signal with a high-order modulated telemetry stream. To achieve the goal, we study the feasibility of pairing the PN ranging with filtered high-order modulations in satellite payload telemetry links and investigate the simultaneous demodulation of the telemetry stream while tracking the ranging sequence. Accordingly, we design a receiver scheme that is able to perform a closed-loop parallel cancellation of the ranging and the telemetry signal, reciprocally. From our analysis, we find that the non-constant envelope property, characterizing the considered modulation set, causes an additional jitter on the PN ranging timing estimation that, on the other hand, can be controlled and reduced by properly sizing the receiver loop bandwidth, without limiting the timing synchronization dynamic. Our study proves that the use of filtered high-order modulations combined with PN ranging outperforms the state-of-the-art in terms of spectral efficiency and achievable data rate while having comparable ranging performance