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This paper studies the high telepresence control for the relay communication based space teleoperation. High telepresence requires real-time, accurate force perception and good position tracking, but all of them are destroyed or affected by time delay. To eliminate the influence of time delay, direct recursive generalized predictive control (DR-GPC) is quoted into this paper to realize position tracking. As for the other two properties, the pseudo position-force (Pseudo-PF) feedback strategy (composed of parameter identification and force reconstruction) is a good way as it can provide real-time and precise force feedback when environment change slowly and time delay is relatively small. However, complex and changeable environment and serious and complex time delay in space teleoperation make the environment force parameter available to force reconstruction is outdated and cannot realize accurate force rebuilding. To solve this problem, we propose a dual regression Pseudo-PF feedback strategy. Compared with the traditional one, its biggest change is the introduction of dual regression that consists of time delay prediction and parameter regression. The former predicts time delay and provides it to the latter to determine the forward prediction steps, while the latter regresses the actual latest and precise environment force parameter according to the forward prediction steps. With the cooperation of time delay prediction and parameter regression, the influence of fast changing environment or serious and complex time delay on force reconstruction can be effectively overcome, so as to realize real-time and accurate force feedback. Finally, DR-GPC and dual regression Pseudo-PF feedback strategies cooperate to achieve high telepresence control, and simulation is given to show its effectiveness. • A dual regression Pseudo-PF feedback strategy is proposed. • High teleopresence control for the relay communication based space teleoperation is first studied. • The introduction of dual regression makes the applicability of this method wider. [ABSTRACT FROM AUTHOR]

Future human exploration missions require new concepts of operations since the international roadmap foresees stations with uncrewed periods (e.g. Lunar Gateway) and deep space missions with communication delays making real-time monitoring and control impossible (e.g. any vehicle on its way to or in orbit of Mars). As part of the commitment to achieve human presence in lunar orbit and prepare for missions to Mars, the goal for future operations is to become independent from ground and enable crews to live and work autonomously. However, as a first step towards on-board crew autonomy, the ground segment itself needs to be automated and its functions eventually transferred on-board. For this purpose, this paper introduces a novel tool, based on Columbus operations, conducted at the Columbus Control Center (COL-CC), allowing the interaction between scheduled activities and the commanding infrastructure, by automatically generating a command sequence, transferring the command sequence to the operators' command interface for inspection and approval, and finally sending the commands to the receiver for execution. This tool is implemented as a ground prototype, in order to show how ground operations can be automated and how such a tool can ultimately lead to increased crew autonomy. • Crewed deep-space missions cannot use real-time commanding, due to signal delays. • Real-time commanding is shifted from the ground controller to an on-board system. • An interface allows interaction between crew, mission timeline and command system. • The system is capable of automatically generating commands, based on constraints. • An activity database stores all necessary information for activity execution. [ABSTRACT FROM AUTHOR]

The future of deep space communications encompasses a challenging situation where the current facilities used to communicate with different spacecraft may become saturated as a result of an increasing number of missions and their complexity. From this forecast, the present study intends to provide a solution to saturation problems through strategically-located upgradable relays for Earth–Mars communications. The foremost goal of this paper is to quantitatively uncover the potential enhancements coming from relay placement in strategic orbits between Earth and Mars. Herein, two relay configurations – a.k.a. network topologies – are analyzed: the Lagrange-relays network topology and a circular, homogeneously-distributed satellite constellation, acknowledged here as pearl constellation. The first uses the Earth–Sun system Lagrange points L 3 , L 4 and L 5 as potential locations for the relays, whilst the second defines an optimized orbit between Earth and Mars with 3 or 4 relay satellites. To aid in the analysis, the authors developed an open-sourced piece of software that obtains the link availability as well as the data rate at which two nodes may communicate, taking as a reference the Deep Space Network (DSN) for Earth, and the Mars Reconnaissance Orbiter for Mars. For complex topologies with more than two communicating nodes, the software outputs the end-to-end bit rate and optimal communication route at each time step. Moreover, this product is extensible to analyze and optimize any network topology and could be adapted to be used for contact management and mission planning in the future. The results show that the network-topology proposals are an advantageous option to significantly increase the link availability of Earth–Mars communications. Nevertheless, the Direct-To-Earth (DTE) link always outperforms the multi-hop path due to the limited telecommunication system's capabilities of both the spacecraft and the relays. As a result of this, the study includes an analysis on the requirements of the relay's design in order to make the constellation a beneficial and comparable alternative to the DTE link. This way, the proposed network topologies become a suitable option whom to share with the DSN communications workload, providing enhanced bit rates and data volumes as well as higher availability of the communication. [Display omitted] • Deep space relays in strategic orbits help to improve Earth–Mars communications. • Solar conjunctions may be successfully avoided through relays. • Communication availability is significantly improved; up to continuous visibility. • Reasonable gain enhancements could lead to bit rates comparable to the current ones. • Total downlink data volume could be tripled. [ABSTRACT FROM AUTHOR]

Large deployable antennas are required for the advancement of space communications, Earth observation, radio astronomy and deep space exploration. Most contemporary space antennas have exceeded the size of launching vehicles, leading to the necessity of stowed concepts to overcome the limitation. Many structural models have been investigated by different organizations. Generally, mesh deployable reflectors are currently more mature compared to other foldable solutions. This will be the topic of this paper. Orbital disturbances, perturbations originated by on-board sources and thermal deformations affecting the deployed configuration can deteriorate the accuracy of the communications system. Undesired dynamic behaviour of structural components has to be predicted and counteracted. Therefore, vibration control is a key technology to correct the distortions altering the proper functioning of the system. An intelligent active structure is introduced as a structure configured with distributed actuators and sensors and guided by a controller to modify the dynamic response of the system. In this paper, the supporting structure of a very large mesh reflector is described. A FEM formulation is adopted to assemble the frame and it is validated by comparing it with commercial codes. According to the adopted model, the active elements can be embedded in the middle of the truss elements. Of course, active control of all the devices at the same time requires a control effort which could be not affordable in space applications. However, the effectiveness is not the same for all the actuators. In this study, two cascade optimization procedures are performed to assess the best positioning and velocity feedback gains of the actuators that must be controlled to damp vibrations. In particular, a gradient-based technique is used after both a Genetic Algorithm and a Reinforcement Learning methodology to find the best set of gains for the controller. The objective function is set as a weighted sum of power consumption of the actuators. As a study case, the spacecraft implements a velocity feedback strategy when performing a generic attitude manoeuvre to coordinate the simultaneous action of the devices to ensure the damping performance of the system is enhanced. In addition, the impact of damaged actuators and uncertainties on the mechanical properties of the passive structure has been discussed and analysed. • Dynamics and control of large space structures. • Vibration suppression via smart materials. • Active truss-like structures modeling. • Genetic Algorithm and Reinforcement Learning methodology for optimization. • Robustness of the controller is verified by means Monte Carlo analysis. [ABSTRACT FROM AUTHOR]

We have shown in paper I of this series [1] that interstellar communication to nearby (pc) stars is possible at data rates of bits per second per Watt between a 1 m sized probe and a large receiving telescope (E-ELT, 39 m), when optimizing all parameters such as frequency at 300–400 nm. We now apply our framework of interstellar extinction and quantum state calculations for photon encoding to the solar gravitational lens (SGL), which enlarges the aperture (and thus the photon flux) of the receiving telescope by a factor of > 10 9 . For the first time, we show that the use of the SGL for communication purposes is possible. This was previously unclear because the Einstein ring is placed inside the solar coronal noise, and contributing factors are difficult to determine. We calculate point-spread functions, aperture sizes, heliocentric distance, and optimum communication frequency. The best wavelength for nearby ( < 100 pc) interstellar communication is limited by current technology to the UV and optical band. To suppress coronal noise, an advanced coronograph is required, alternatively an occulter could be used which would require a second spacecraft in formation flight 78 km from the receiver, and ≈ 10 m in size. Data rates scale approximately linear with the SGL telescope size and with heliocentric distance. Achievable (receiving) data rates from α Cen are of order 10 Mbits per second per Watt for a pair of meter-sized telescopes, an improvement of 10 7 compared to using the same receiving telescope without the SGL. A 1 m telescope in the SGL can receive data at rates comparable to a km-class “normal” telescope. [ABSTRACT FROM AUTHOR]

Abstract: In a sequence of papers on the topic of message construction for interstellar communication by means of a cosmic language, the present author has discussed various significant requirements such a lingua should satisfy. The author’s Lingua Cosmica is a (meta) system for annotating contents of possibly large-scale messages for ETI. LINCOS, based on formal constructive logic, was primarily designed for dealing with logic contents of messages but is also applicable for denoting structural properties of more general abstractions embedded in such messages. The present paper explains ways and means for achieving this for a special case: recursive entities. As usual two stages are involved: first the domain of discourse is enriched with suitable representations of the entities concerned, after which properties over them can be dealt with within the system itself. As a representative example the case of Russian dolls (Matrjoshka’s) is discussed in some detail and relations with linguistic structures in natural languages are briefly exploited. [Copyright &y& Elsevier]

Abstract: Many important SETI terms are either ambiguously defined or interpreted by different experts differently. Based on the author''s experience with astronautical terminology (IAA multilingual space dictionary) a summary of the usual problems connected with an uniform definition of fundamental terms is attempted. In the second part several examples are quoted from the SETI literature—including the terms ETI, SETI and METI themselves, the definition of a habitable zone, of alien life, of an extraterrestrial artifact, of the Drake equation, of the Fermi-paradox, etc. In the third part of the paper a new task for the SETI social sciences community is raised, namely to collect “Lasting Universal Terms”; i.e. terms the meaning of which did not change since millennia, are independent on geographic position and also on the terrestrial environment and biology. Such terms might be preferably used in interstellar communication. All these questions are related to the manner how we might think about ETI and SETI in new ways. The paper tries to summarize the problems connected with exact SETI terminology and its potential implications for the future. [Copyright &y& Elsevier]

Abstract: The present overview covers the period from 1820 to the beginning of the 20th century. Emphasis is laid on the latter half of the 19th century because many efforts have been done at that time to elaborate schemes for contacting our neighboring planets by interplanetary telegraphy. This period knew many advances not only in planetary studies but also in the nascent field of telecommunications. Such a context led astronomers who were also interested in the problem of planetary habitability, to envisage that other planets could be contacted, especially the planet Mars. Interplanetary communication using a celestial telegraphy was planned during this period of great speculations about life on Mars. This paper focuses on four authors: the Frenchmen C. Flammarion, Ch. Cros, A. Mercier and the Serbian N. Tesla, who formulated early proposals to communicate with Mars or Venus. The first proposals (which remained only theoretical) showed that an initial reflection had started as early as the second part of the 19th century on the type of language that could be both universal and distinguishable from a natural signal. Literary history of interplanetary communication preceded by far the scientific one. Authors of the 1900s were very prolific on this topic. French fictions are mentioned in this paper as examples of such a literature. This incursion into selected texts stresses the fact that the problem of techniques and messages employed to communicate with other planets goes beyond the strict scientific framework. Finally, this paper aims to highlight the similarities as well as the differences between the different proposals and to underline what that could possibly help present SETI research to define messages supposed to be sent to other planetary systems. [Copyright &y& Elsevier]

Abstract: Suppose the international SETI effort yields the discovery of some signal of evidently non-natural origin. Could it contain linguistic information formulated in some kind of Lingua Cosmica? One way to get insight into this matter is to consider what specific (bio) linguistic signature(s) could be attached to a cosmic language for interstellar communication—designed by humans or an alien society having reached a level of intelligence (and technology) comparable to or surpassing ours. For this purpose, we consider in the present paper the logico-linguistic system LINCOS for (A)CETI, developed during a number of years by the author in several papers and a monograph . The system has a two-fold signature, which distinguishes it significantly from natural languages. In fact abstract and concrete signatures can be distinguished. That an abstract kind occurs is due to the manner in which abstractions of reality are represented in LINCOS-texts. They can take compound forms because the system is multi-expressive—partly due to the availability of inductive (recursive) entities. On the other hand, the concrete signature of LINCOS is related to the distribution of delimiters and predefined tokens in texts. Assigning measures to concrete signatures will be discussed elsewhere. The present contribution concentrates on the abstract signature of the language. At the same time, it is realized that an alien Lingua Cosmica might, but not necessarily needs to have this kind of signatures. [Copyright &y& Elsevier]

Abstract: Hopes of sending probes to another star other than the Sun are currently limited by the maturity of advanced propulsion technologies. One of the few candidate propulsion systems for providing interstellar flight capabilities is nuclear fusion. In the past many fusion propulsion concepts have been proposed and some of them have even been explored in detail, Project Daedalus for example. However, as scientific progress in this field has advanced, new fusion concepts have emerged that merit evaluation as potential drivers for interstellar missions. Plasma jet driven Magneto-Inertial Fusion (PJMIF) is one of those concepts. PJMIF involves a salvo of converging plasma jets that form a uniform liner, which compresses a magnetized target to fusion conditions. It is an Inertial Confinement Fusion (ICF)–Magnetic Confinement Fusion (MCF) hybrid approach that has the potential for a multitude of benefits over both ICF and MCF, such as lower system mass and significantly lower cost. This paper concentrates on a thermodynamic assessment of basic performance parameters necessary for utilization of PJMIF as a candidate propulsion system for the Project Icarus mission. These parameters include: specific impulse, thrust, exhaust velocity, mass of the engine system, mass of the fuel required etc. This is a submission of the Project Icarus Study Group. [Copyright &y& Elsevier]

Abstract: Spread spectrum, widely employed in modern digital wireless terrestrial radio systems, chooses a signal with a noise-like character and much higher bandwidth than necessary. This paper advocates spread spectrum modulation for interstellar communication, motivated by robust immunity to radio-frequency interference (RFI) of technological origin in the vicinity of the receiver while preserving full detection sensitivity in the presence of natural sources of noise. Receiver design for noise immunity alone provides no basis for choosing a signal with any specific character, therefore failing to reduce ambiguity. By adding RFI to noise immunity as a design objective, the conjunction of choice of signal (by the transmitter) together with optimum detection for noise immunity (in the receiver) leads through simple probabilistic argument to the conclusion that the signal should possess the statistical properties of a burst of white noise, and also have a large time-bandwidth product. Thus spread spectrum also provides an implicit coordination between transmitter and receiver by reducing the ambiguity as to the signal character. This strategy requires the receiver to guess the specific noise-like signal, and it is contended that this is feasible if an appropriate pseudorandom signal is generated algorithmically. For example, conceptually simple algorithms like the binary expansion of common irrational numbers like are shown to be suitable. Due to its deliberately wider bandwidth, spread spectrum is more susceptible to dispersion and distortion in propagation through the interstellar medium, desirably reducing ambiguity in parameters like bandwidth and carrier frequency. This suggests a promising new direction in interstellar communication using spread spectrum modulation techniques. [Copyright &y& Elsevier]

Abstract: The SETI community is becoming increasingly interested in extending its searches to include wideband signals, such as information-bearing beacons. However, prior to discovery of a target signal, a SETI receiver has no knowledge of the signal parameters (bandwidth, carrier frequency, modulation type, etc.) and so detection can be very challenging, especially at low signal-to-noise ratios. However, this paper shows by example that there exist signal classes and corresponding detection methods that permit straightforward discovery of wideband signals of unknown structure. The example given is a form of binary antipodal signalling that utilises spread-spectrum modulation, which offers benefits to the receiver in terms of immunity to noise/interference and ease of detection. The proposed detection method is a ‘symbol-wise’ autocorrelation process that takes advantage of the cyclostationarity property of modulated signals. Detection sensitivity is suboptimal in comparison with what is possible if the target signal structure is known. However, this deficit can be overcome by processing longer timespans of signal, providing scope for detection at extremely low signal-to-noise ratios. It is postulated that antipodal signalling represents an attractive option for interstellar beacons because it is both power efficient and there exists a simple complementary detection method not requiring explicit coordination between the transmitter and receiver. This in turn suggests there is a case for extending future SETI searches to include this class of signal. [Copyright &y& Elsevier]

Abstract: Interplanetary communication networks comprise orbiters, deep-space relays, and stations on planetary surfaces. These networks must overcome node mobility, constrained resources, and significant propagation delays. Opportunities for wireless contact rely on calculating transmit and receive opportunities, but the Euclidean-distance diameter of these networks (measured in light-seconds and light-minutes) precludes node discovery and contact negotiation. Propagation delay may be larger than the line-of-sight contact between nodes. For example, Mars and Earth orbiters may be separated by up to 20.8min of signal propagation time. Such spacecraft may never share line-of-sight, but may uni-directionally communicate if one orbiter knows the other''s future position. The Contact Graph Routing (CGR) approach is a family of algorithms presented to solve the messaging problem of interplanetary communications. These algorithms exploit networks where nodes exhibit deterministic mobility. For CGR, mobility and bandwidth information is pre-configured throughout the network allowing nodes to construct transmit opportunities. Once constructed, routing algorithms operate on this contact graph to build an efficient path through the network. The interpretation of the contact graph, and the construction of a bounded approximate path, is critically important for adoption in operational systems. Brute force approaches, while effective in small networks, are computationally expensive and will not scale. Methods of inferring cycles or other librations within the graph are difficult to detect and will guide the practical implementation of any routing algorithm. This paper presents a mathematical analysis of a multi-destination contact graph algorithm (MD-CGR), demonstrates that it is NP-complete, and proposes realistic constraints that make the problem solvable in polynomial time, as is the case with the originally proposed CGR algorithm. An analysis of path construction to complement hop-by-hop forwarding is presented as the CGR-EB algorithm. Future work is proposed to handle the presence of dynamic changes to the network, as produced by congestion, link disruption, and errors in the contact graph. We conclude that pre-computation, and thus CGR style algorithms, is the only efficient method of routing in a multi-node, multi-path interplanetary network and that algorithmic analysis is the key to its implementation in operational systems. [Copyright &y& Elsevier]

Abstract: The feasible rendezvous, flyby and sample return mission scenario to different spectral-type asteroids for the 2015–2025 are investigated. The emphasis is put on the potential target selection and the design of preliminary interplanetary transfer trajectory in this paper. First, according to different scientific motivations, some potential targets with different spectral-type and physical property are selected. Then, some optimal rendezvous and sample return opportunities for different spectral-type asteroids are presented by using pork-chop plots method and Sequential Quadratic-Programming (SQP) algorithm. In order to reduce the launch energy and total velocity increments for sample return mission, the Earth swingby strategy is used. In addition, the feasible trajectory profiles of flyby and rendezvous with two different spectral-type asteroids in one mission are discussed. A hybrid optimization method combing the Differential Evolution (DE) algorithm and SQP algorithm is introduced as a trajectory design method for the mission. Finally, some important parameters of transfer trajectory are analyzed, which would have a direct impact on the design of spacecraft subsystem, such as communication, power and thermal control subsystem. [Copyright &y& Elsevier]

Abstract: Altruism has previously been proposed as a topic for interstellar communication, because it begins to describe one important class of human and non-human behaviors, and because it can be modeled in mathematical and physical terms. Prior research has focused on altruism toward close relatives. The current paper explains how we could communicate basic principles of reciprocal altruism, in which one entity undergoes short-term self-sacrifice for the benefit of another, as well as for long-term self-interest. After providing an algorithmic description of the loss of mass involved in the evolution of stars—a phenomenon that should be familiar to extraterrestrial astronomers—an analogous process is described at a human scale, where the maintenance or loss of mass represents the maintenance or loss of health, and ultimately life. An adaptation of the Prisoner''s Dilemma game is communicated, showing limitations of both cooperation and defection as strategies for interacting with other agents. For the overall stability of a population, there are significant advantages for entities not always either cooperating or defecting in their responses; we end by modeling a more flexible strategy discussed by game theorists, known as Tit For Tat. [Copyright &y& Elsevier]

Abstract: This paper informs how elements of constructive type theory can be used effectively for clarifying textual messages meant for communication with ETI. Within the setting of a suitable environment consisting of declared terms, it is shown how logical contents of texts can be modelled and codified. [Copyright &y& Elsevier]

Abstract: Contemporary narratology (narrative theory) offers a useful framework for interpreting interstellar messages that have already been sent to potential extraterrestrial recipients, as well as for designing messages that may be transmitted in the future. In this paper, narratological concepts are used to analyze in depth a single interstellar message sequence, elucidating methods by which various parts of speech (nouns, verbs, adjectives, and adverbs) can be paired with pictures to describe the human body in motion. The concept of focalization is applied to the message sequence''s use of isolation and magnification, which highlight the structure and function of the human body and its constituent parts. The challenges of interpreting gaps within narratives, as well as the setting in which events occur, are considered. The importance of closure in providing a fitting end to narratives is examined, and the plausibility of creating images that could be interpreted correctly by extraterrestrial intelligence is assessed. Narratological concepts examined here, as well as additional aspects of narrative, provide important resources for future work in interpreting and designing interstellar messages. [Copyright &y& Elsevier]

Abstract: Previous discussions of interstellar messages that could be sent to extraterrestrial intelligence have focused on descriptions of mathematics, science, and aspects of human culture and civilization. Although some of these depictions of humanity have implicitly referred to our aspirations, this has not clearly been separated from descriptions of our actions and attitudes as they are. In this paper, a methodology is developed for constructing interstellar messages that convey information about our aspirations by developing a taxonomy of maxims that provide guidance for living. Sixty-six maxims providing guidance for living were judged for degree of similarity to each of other. Quantitative measures of the degree of similarity between all pairs of maxims were derived by aggregating similarity judgments across individual participants. These composite similarity ratings were subjected to a cluster analysis, which yielded a taxonomy that highlights perceived interrelationships between individual maxims and that identifies major classes of maxims. Such maxims can be encoded in interstellar messages through three-dimensional animation sequences conveying narratives that highlight interactions between individuals. In addition, verbal descriptions of these interactions in Basic English can be combined with these pictorial sequences to increase intelligibility. Online projects to collect messages such as the SETI Institute''s Earth Speaks and La Tierra Habla, can be used to solicit maxims from participants around the world. [Copyright &y& Elsevier]

Abstract: The present paper is a synthesis of three presentation given by myself at the Toulouse IAC 2001 (Analogy as a tool to communicate abstract concepts in SETI), the Bremen IAC 2003 (From maths to culture: towards an effective message), and the Vancouver IAC 2004 (Philosophical and religious implications of extraterrestrial intelligent life). Its aim is to find a way to make our cultural concepts understandable to hypothetical extraterrestrials (ETs) in a SETI communication. First of all, I expose the reasons why I think that analogy could be a good tool for this purpose. Then, I try to show that this is possible only in the context of an integrated language, using both abstract symbols and pictures, also sketching two practical examples about some basic concepts of our moral and religious tradition. Further studies are required to determine whether this method could be extended to the higher-level abstract concepts in the other fields of our culture. Finally, I discuss the possible role of mathematics, logic and natural science in the construction of an analogy-based language for interstellar messages with a cultural content and a possible way of managing this matter from a social point of view. [Copyright &y& Elsevier]

Abstract: This paper looks at the immense difficulties involved in trying to decipher the content of a signal, when the world''s fears and expectations would be for immediacy of information. It is a reasonable assumption that having announced a signal is from an ET source that the next question will be “is there a message?” To put this task into context, we still have many scripts from our own antiquity that remain undeciphered, despite many serious attempts, over hundreds of years. So, given this, an algorithmic rationale, based on previous research into signal decipherment techniques, is presented. This phased approach will then provide an initial methodology for us attempting to unlock the content of an extra-terrestrial signal, whilst facilitating the dissemination of timely and accurate information to an expectant world. [Copyright &y& Elsevier]

Abstract: The aim of HuLCC (the human language chorus corpus), is to provide a resource of sufficient size to facilitate inter-language analysis by incorporating languages from all the major language families: for the first time all aspects of typology will be incorporated within a single corpus, adhering to a consistent grammatical classification and granularity, which historically adopt a plethora of disparate schemes. An added feature will be the inclusion of a common text element, which will be translated across all languages, to provide a precise comparable thread for detailed linguistic analysis for translation strategies and a mechanism by which these mappings can be explicitly achieved. Methods developed to solve unambiguous mappings across these languages can then be adopted for any subsequent message authored by the SETI community. Initially, it is planned to provide at least 20,000 words for each chosen language, as this amount of text exceeds the point where randomly generated text can be disambiguated from natural language and is of sufficient size useful for message transmission (Elliot, 2002). This paper details the design of this resource, which ultimately will be made available to SETI upon its completion, and discusses issues ‘core’ to any message construction. [Copyright &y& Elsevier]

Abstract: Despite the fact that major efforts have been expended on passive searches for extraterrestrial signals, few deliberate “transmissions” to potential alien recipients have occurred. These have generally taken the form of simple graphics depicting such things as our appearance, location, and biological construction. In this paper, we consider (a) the fundamental technical and astronomical limitations to interstellar messaging—in other words, how many “bits” could any society reasonably send, and (b) what might be a likely transmission strategy. These considerations suggest approaches for SETI programs, as well as giving insight into the types of messages we might construct for eventual replies to received signals. [Copyright &y& Elsevier]

Abstract: The gravitational lens of the Sun is an astrophysical phenomenon predicted by Einstein’s general theory of relativity. It implies that if we can send a probe along any radial direction away from the Sun up to the minimal distance of 550AU and beyond, the Sun’s mass will act as a huge magnifying lens, letting us “see” detailed radio maps of whatever may lie on the other side of the Sun even at very large distances. The recent book by this author (Claudio Maccone, Deep Space Flight and Communications, 414 pages, Praxis-Springer, 2009) describes such future FOCAL space missions to 550AU and beyond. In this paper, however, we want to study another possibility yet: how to enable the future interstellar radio links between the solar system and any future interstellar probe by utilizing the gravitational lens of the Sun as a huge antenna. In particular, we compare the bit error rate (BER) across interstellar distances with and without using the gravitational lens effect of the Sun. The conclusion is that only when we will exploit the Sun as a gravitational lens we will be able to communicate with our own probes (or with nearby Aliens) across the distances of even the nearest stars to us in the Galaxy and that at a reasonable bit error rate. Furthermore, we study the radio bridge between the Sun and any other Star that is made up by the two gravitational lenses of both the Sun and that Star. The alignment for this radio bridge to work is very strict, but the power saving is enormous, due to the huge contributions of the two stars’ lenses to the overall antenna gain of the system. For instance, we study in detail: [1)] The Sun–Alpha Cen A radio bridge. [2)] The Sun–Barnard’s star radio bridge. [3)] The Sun–Sirius A radio bridge. [4)] The radio bridge between the Sun and any Sun-like star located in the galactic bulge. [5)] The radio bridge between the Sun and any Sun-like star located inside the Andromeda galaxy (M 31). The conclusion is that a radio interstellar communications network can indeed be built if the gravitational lenses of all stars involved are exploited. Then, the new question arises: has any advanced civilization already built such a radio telecommunication network? If so, our current and future SETI searches should be tuned-up to match with this newly realized possibility. [Copyright &y& Elsevier]

Abstract: Some characteristics of terrestrial music may be meaningful to extraterrestrial civilizations by virtue of the connection between acoustics and mathematics—both of which might be known by technologically advanced extraterrestrial intelligence. For example, a fundamental characteristic of terrestrial polyphonic music is found the number of tones used various scales, insofar as the number of tones represents a compromise between competing musical demands; the number of tones in a scale, however, also reflects some of the perceptual characteristics of the species developing that music. Thus, in the process of communicating something about the structure of terrestrial music through interstellar messages, additional information about human perceptual and cognitive processes can also be conveyed. This paper also discusses methods for sending signals that bear information through the form of the very frequencies in which the signals are transmitted. If the challenges of creating intelligible messages are greater than often thought, the advantage of reduced conventionality of encoding the message by using an iconic format of this sort may be of significant value. Such an approach would allow the incremental introduction of musical concepts, somewhat akin to the step-by-step tutorials in mathematics and logic that form the basis of Freudenthal''s Lincos. [Copyright &y& Elsevier]

Abstract: In this paper, I am interested in exploring the potential of ritual performance as a means of communication with ETI. I argue that the study of ritual and ritualized behavior, understood as a technique for representation of meaning and meaningfulness about the world, has potential to inform how scientists think about the construction and interpretation of interstellar messages. I do not suggest that ritual activities themselves provide more than limited potential for communication with ETI. However, the structural elements of ritual and the manner in which meaning is conveyed through the formality and repetition of ritual is at least to some extent decipherable cross-culturally and provides one way to think about how to express important aspects of humans and their cultures to ETI and to represent, if not specific meanings themselves, the fact that a message is meaningful. [ABSTRACT FROM AUTHOR]

Abstract: In a sequence of papers on the topic of message construction for interstellar communication by means of a cosmic language, representations of various kinds of concepts of reality in a Lingua Cosmica system . Those studied were logic relations of a static character. The present contribution contains an important, fundamental extension: groundwork is done for the purpose of interpreting (dynamic) processes of various sorts in the linguistic system. Individual processes are abstracted in a logic sense and provided with basic properties as termination and communication functions. They can be combined into kinds of processes: sequential and parallel ones represented by only one inductive definition in logic. Based on concepts from the so-called process algebra, processes are provided with channels mapping them to their states. State vectors are introduced to represent states of conglomerates of processes. Communication between processes (locally or globally) is effectuated by means of state transitions. Together with a programmed arbitration function, state vectors play a crucial role in representing communication. With these ingredients possibilities for general interpretations of a wide range of processes in the Lingua Cosmica system come in view. [Copyright &y& Elsevier]