Distributed Space Traffic Management Solutions with Emerging New Space Industry

Day-to-day services, from weather forecast to logistics, rely on space-based infrastructures whose integrity is crucial to stakeholders and end-users worldwide. Current trends point towards congestion of the near-Earth space environment increasing at a rate greater than existing systems support, and thus demand novel cost-efficient approaches to traffic detection, characterization, tracking, and management to ensure space remains a safe, integral part of societies and economies worldwide. Whereas machine-learning (ML) and artificial intelligence (AI) have been extensively proposed to address congestion and alleviate big-data problems of the future, little has been done so far to tackle the need for transnational coordination and conflict-resolution in the context of space traffic management (STM). In STM, there is an ever-growing need for distributing information and coordinating actions (e.g., avoidance manoeuvres) to reduce the operational costs borne by individual entities and to decrease the latencies of actionable responses taken upon the detection of hazardous conditions by one-to-two orders of magnitude. However, these needs are not exclusive to STM, as evidenced by the widespread adoption of solutions to distributing, coordinating, and automating actions in other industries such as air traffic management (ATM), where a short-range airborne collision avoidance system (ACAS) automatically coordinates evasive manoeuvres whenever a conjunction is detected. Within this context, this paper aims at establishing a roadmap of promising technologies (e.g., blockchain), protocols and processes that could be adapted from different domains (railway, automotive, aerial, and maritime) to build an integrated traffic coordination and communication architecture to simplify and harmonise stakeholders’ satellite operations. This paper is organised into seven sections. First, Section 1 introduces the problem of STM, highlighting its complexity. Following this introduction, Section 2 discusses needs and requirements of various stakeholders such as commercial operators, space situational awareness (SSA) service providers, launch-service providers, satellite and constellation owners, governmental agencies, regulators, and insurance companies. Then, Section 3 addresses existing gaps and challenges in STM, focusing on globally coordinated approaches. Next, Section 4 reviews technologies for distributed, secure, and persistent communications, and proposed solutions to address some of these challenges from non-space sectors. Thereafter, Section 5 briefly covers the history of STM proposals and presents the state-of-the-art solution being proposed for modern STM. Following this review, Section 6 devises a step-by-step plan for exploiting and deploying some of the identified technologies within a five-to-ten-year timeline to close several existing gaps. Finally, Section 7 concludes the paper

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

Sparse Satellite Constellation Design for Global and Regional Direct-to-Satellite IoT Services

International audienceIn this paper we introduce and design sparse constellations for Direct-to-Satellite Internet of Things (DtS-IoT). DtS-IoT does not require a ground infrastructure, because the devices are directly connected to Low Earth Orbit satellites acting as orbiting gateways. The key idea of sparse constellations is to significantly reduce the number of in-orbit DtS-IoT satellites by (i) a proper dimensioning of the delivery delay anyway present in resource-constrained IoT services, and (ii) an optimal positioning of the orbiting gateways. First, we analyze LoRa/LoRaWAN and NB-IoT standards and derive realistic constraints on the maximum gap time between two consecutive passing-by satellites. Then, we introduce and optimize an algorithm to design quasioptimal topologies for sparse IoT constellations. Finally, we apply our design to both global and regional coverage and we analyze the trade-off between latency, number of orbit planes and total number of satellites. Results show that sparse constellations can provide worldwide IoT coverage with only 12.5% and 22.5% of the satellites required by traditional dense constellations considering 3-hour and 2-hour gaps. Also, we show that regionspecific coverage of Africa and Europe can be achieved with only 4 and 3 satellites for LoRa/LoRaWAN and NB-IoT, respectively