This study presents a Digital Twin (DT) that is being created to optimize the use of the available hydric resources, and mitigate the effects of the increasing water shortage in irrigated agriculture in fields in the Urgell channel region (Lleida). A DT is "a virtual representation of an object or system that spans its lifecycle, it is updated from real-time data, and uses simulation, machine learning and reasoning to help decision-making." It will model the water fluxes using the knowledge of the amounts of water taken in, used, and returned to the environment, and other parameters that impact the water budget, such as atmospheric variables (temperature, water vapor deficit, relative humidity, solar radiance…), surface soil moisture, and evapotranspiration maps, etc. Satellite Earth Observation (EO) data, collocated with in-situ data from a network of 20 soil moisture probes and 2 meteo stations will be used to train the DT. Additionally, a rover-based ground penetrating radar will be used for cross-calibration.

The escalating volume of road users and the increase on safety demands by the governmental institutions, such as the EU, highlights the need for more widespread and advanced traffic monitoring systems. Despite the emergence of traffic monitoring solutions through Earth observation techniques, persistent challenges are evident, particularly in the context of remote and rural roads. This paper presents an innovative approach, integrating ground-based imaging, in-situ Computer Vision (CV) and Direct-to-Satellite Internet of Things (DtS-IoT) for a near-real-time, cost-effective traffic monitoring solution. Focusing on current challenges, this hybrid system demonstrates to be a tailored response to the demands of remote traffic monitoring, showcasing feasibility through a proof-of-concept integrated solution.

From the irruption of the New Space paradigm, a multitude of disruptive initiatives and cutting-edge technologies emerged in the space sector, resulting in the creation of new vertical domains. In recent years, satellite systems have been envisaged for communications to provide ubiquitous, global, and broadband services. However, the demanding requirements can only be met by large Low Earth Orbit satellite constellations (i.e., mega-constellations). This industry of massive space-based networks, currently led by SpaceX, is converging with the 3GPP Non-Terrestrial Networks market due to their common trend. For this purpose, satellite operators are partnering with Mobile Network Operators to access their 3GPP-compliant frequency spectrum and implement Direct-to-Handset technologies. Nevertheless, mega-constellations pose major problems to multiple global ecosystems. This paper delves into the economic, governance, sustainability, astronomical, and coexistence issues arising from the mega-constellation industry and offers a new perspective on how the space ecosystem should evolve to avoid collapse.

Non-Terrestrial Networks are three-dimension net-works composed of aircraft and spacecraft nodes that extend the services provided by terrestrial infrastructure. This kind of network plays a key role in the deployment of Internet of Things (IoT) connectivity in remote areas, which are more probable to currently lack it. Among the different alternatives, the usage of satellite systems to conform these new networks that provides IoT connectivity has emerged as a promising solution. In this scenario, IoT devices directly interacts with satellites with Low-Power Wide Area Network technologies. This approach is defined in the literature as a Direct-to-Satellite IoT (DtS-IoT) architecture. This work contributes to the DtS-IoT concept by presenting an experimental deployment following this architecture. Specifically, a dedicated sensor that monitors water reservoirs located in remote areas are installed. The sensor collects the status of the reservoirs and uploads it to the satellite. This application becomes essential for the maintenance of the firefighter infrastructure, which typically is located in the mountains. This work presents thus the architecture design, the sensor setup, and discusses the achieved results of an in-field campaign. These results demon-strate the feasibility of this deployment with current technologies, and promotes its deployment in future projects.

Due to the fact that large swathes on Earth still lack broadband communication coverage, especially in remote/rural areas and developing countries, there have been several attempts, starting from 3GPP Release 17, to lay out the architectural amendments needed for the integration of terrestrial networks with their non-terrestrial counterparts. Such attempts have led to recent projects regarding such integration that consider either 5G/5G-Advanced networks or more revolutionary approaches for the forthcoming 6G networks. In this manuscript, we give an overview of the architectural framework, technical innovations, and considered use cases of the Horizon Europe ETHER project.

The evolution of nonterrestrial networks (NTNs) will require some conceptual changes in the communication paradigm established in common cellular and low-power networks. This will be paramount in sparse low Earth orbit (LEO) satellite constellations that cannot ensure service continuity. Limited satellite access time for terrestrial devices and the typical Internet of Things (IoT) duty-cycled application will require coordination mechanisms, so that desired sleep and wake-up periods can be synchronized with satellite availability. Toward this coordination, this work first characterizes the access time of LEO satellites for terrestrial devices. It then evaluates the model proposed by 3GPP for orbit determination, the simplified general perturbation 4 (SGP4), in terms of accuracy and energy saving from the low power point of view. From the evaluation, a novel method is proposed based on relaxing the periodic updates of satellite orbital information required by SGP4 to increase the battery life of IoT-NTN devices. The method is enhanced with a function that matches the uncertainty in the access estimates to a wake-up guard time, improving, and guaranteeing access success. Finally, the proposal is validated using data from a real communication link between a terrestrial device and the Enxaneta LEO CubeSat (3B5GSAT).

Novel demands from Earth Observation community have emerged in last years. They are mainly oriented on monitoring geo-information and human activity impact. These applications require satellite systems capable to provide high frequency and sub-metric spatial resolution observations. An hybrid architecture which combines in-space with in-situ measurements emerges as a potential approach. In this scenario, ground sensor devices autonomously perform in-situ measurements that are later on combined with satellite ones. This work extends the research on architecture by presenting two proof-of-concept of potential applications: (1) irrigation monitoring, and (2) livestock tracking. This work focuses on the deployment of IoT devices (developed in previous research activities) to extract data for these applications. The results are discussed, and they demonstrate the viability to monitor the trend of crop metrics, as well as the position of a cow herd over time. These results encourage to keep developing these demonstrations for further applications.

Novel demands from Earth Observation community have emerged due to current climate situation. These needs are mainly oriented on monitoring hydric stress, climate disasters, among others. These applications require satellite systems capable to provide high frequency and sub-metric spatial resolution observations. An hybrid architecture which combines in-space with in-situ measurements emerges as a potential approach. In this scenario, ground sensor devices autonomously perform in-situ measurements with different spatial and temporal resolutions different from satellite ones. These devices must manage their constrained resources and transfer the generated data. The Direct-to-Satellite Internet of Things paradigm proposes the interconnection of Low Earth Orbit satellites with these devices using standardized protocols. This work presents a proof-of-concept that demonstrates the benefits for Earth Observation applications. Specifically, a sensor system is developed to monitor the soil moisture, and installed in a remote location to perform a measurement campaign. The results demonstrate the feasibility of this hybrid architecture.

FSSCat, the “Federated Satellite Systems/3Cat-5” mission was the winner of the 2017 ESA S^3 (Sentinel Small Satellite) Challenge and overall winner of the Copernicus Masters competition. FSSCat consists of two 6 unit cubesats carrying on board UPC's Flexible Microwave Payload - 2 (FMPL-2), an L-band microwave radiometer and GNSS-Reflectometer implemented in a software defined radio, and Cosine's HyperScout-2 visible and near infrared + thermal infrared hyperspectral imager, enhanced with PhiSat-1, a on board Artificial intelligence experiment for cloud detection. Both spacecrafts include optical and UHF inter-satellite links technology demonstrators, provided by Golbriak Space and UPC, respectively. This paper describes the mission, and the main scientific results of the FMPL-2 obtained during the first three months of the mission, notably the sea ice concentration and thickness, and the downscaled soil moisture products over the Northern hemisphere.

Global change and sea level rise are increasing the interest in monitoring oceans, and specially the Arctic. L-band microwave radiometers can be used for thin sea ice thickness and oceans monitoring, and these maps are being routinely generated from SMOS [1] and SMAP [2], which if combined with imagers provide a higher resolution. The CubeSat-based payload RITA (RadIomeTry and vegetation Analysis) plans to address those monitoring needs by including an IoT enabled payload, a hyperspectral imager and an L-band microwave radiometer with RFI detection and mitigation [3]. The IoT payload implements an SDR-based LoRa modulation and it will be used to perform On-Demand executions of the radiometer and the imager payloads on-board RITA. As part of this work, an in-depth description of the objectives, concept of operations and hardware and software architecture and implementation of the IoT LoRa module will be provided.

The Flexible Microwave Payload -2 is the microwave remote sensing payload of the FSSCat mission. The instrument is the outcome of years of work of the Universitat Politécnica de Catalunya Passive Remote Sensing Laboratory, and the NanoSat-Lab. The FSSCat mission was launched on board the Vega VV16, on September the 3rd, 2020. The instrument was executed for the very first time on September the 16th, 2020, and it was commissioned less than two weeks later. This extended abstract presents the geo-located FMPL-2 measurements, which consist of a Global Navigation Satellite System - Reflectometer and an L-band radiometer. The performance of the instrument and preliminary level 1C results are presented, showing that CubeSats can to perform passive microwave remote sensing scientific missions.

The celebration of the International Polar Year in 2007 remarked the necessity to better monitor the polar regions. Moreover, the H2020 “Operational Network of Individual Observation Nodes” (ONION) project analyzed and proposed an overall EU strategy and technical guidelines to develop and implement innovative Earth Observation concepts in the time frame 2021-2027. The top priority that was identified was the Maritime Weather Forecast, and in particular the Arctic sea ice monitoring use-case. Currently, those needs have been addressed with remote sensing satellites or in-situ instruments. However, in-situ instruments often sink or crash with ice blocks. Additionally, these instruments are isolated, making challenging its deployment and the data retrieval, using LEO satellite communications (e.g. Iridium, OrbComm). This also poses a problem in terms of modularity and flexibility, since sensors rely on proprietary communication systems. This work proposes a modular and cost-effective solution to this problem applying the paradigm of the Internet of Things to this context. Particularly, Long Range (LoRa) is one of the most frequently used and efficient technologies that also ensures long ranges. As part of the presented work, a satellite constellation is proposed, analyzed to cover the Arctic region. The maximum number of sensors simultaneously using the LoRa technology is also evaluated.

In the last years, the need to access Earth Observation high spatial resolution data with very low latency, ideally in near-real-time, has increased. Distributed Satellite Systems have emerged as an effective and efficient architecture to deal with these tight requirements. One of these systems is the Federated Satellite Systems which explore the benefits of sharing unused and available resources between satellites, such as memory storage or downlink opportunities. This interaction is known as satellite federations. Additional downlink contacts may enable low-latency communications and increase the downlink capacity. Therefore, the deployment of federations would allow satisfying current Earth Observation community demands. This work contributes to establish this promising paradigm by presenting a proof-of-concept of a federated system, called FSS Experiment payload. This payload is boarded into three stratospheric balloons, and it provides them communications means to create federations. The design of the payload, and the flight campaign results are presented in this work. These results demonstrate the feasibility of deploying federations, as well as the benefits of deploying them in future EO missions.

During these years, novel Distributed Satellite Systems (DSS) have addressed the new Earth Observation (EO) requirements (e.g. near-real time access to data, or multi-point observations). One of the DSS proposals is the concept of Federated Satellite System (FSS) which has explored the benefits of sharing available and unused resources between satellite to maximize the system utility. The possibility to use additional downlink opportunities thanks to federations is a resource that could improve current EO missions, and thus achieving the required performance. For that reason, the FSS Experiment payload has been implemented as a FSS proof-of-concept between 6-Unit CubeSats in the FSSCAT mission. This article presents the design, and the test results of this payload demonstrating its feasibility for future EO missions.

Global Navigation Satellite System Reflectometry and L-band microwave radiometry have been used for soil moisture, biomass, and cryosphere studies. Combining both technologies in a low-power and cost-effective solution could largely improve current Earth observations.3Cat-4 mission is a 1-Unit CubeSat technology demonstrator of the Flexible Microwave Payload - 1, a reduced size payload that combines these two technologies. This work presents the objectives of the3Cat-4 mission and the details of the spacecraft architecture and performance. Each spacecraft subsystem is detailed at hardware and software levels. In addition, the presented results indicate that the current spacecraft design will survive the flight conditions (i.e. thermal and structural ones).

The FSSCat mission is a two nano-satellite Earth Observation mission based on 6-unit CubeSats. This paper is focused on the description of one of the remote sensing payloads: the Flexible Microwave Payload 2 (FMPL-2), on board the3Cat-5/A. The payload design is based on a Software Defined Radio, aiming to demonstrate the capabilities of nano-satellites to provide valuable scientific data. Two different instruments are integrated into a single payload: a multi-constellation (GPS and Galileo) Global Navigation Satellite System Reflectometer (GNSS-R), and a Total Power Radiometer (TPR) with Radio Frequency Interference (RFI) detection and mitigation capabilities. This paper presents the payload design, and the tests conducted during the qualification campaign.

The Flexible Microwave Payload 2 (FMPL-2) is a Remote Sensing payload carried on board3Cat-5/A, one of the two 6-unit CubeSats of the FSSCat mission. FMPL-2 is a payload based on a Software Defined Radio (SDR), integrating two instruments in a single platform: a multi-constellation (GPS and Galileo) Global Navigation Satellite System Reflectometer (GNSS-R), and a Total Power Radiometer (TPR) with Radio Frequency Interference (RFI) detection and mitigation capabilities. This paper focuses on the description of the software developed for the platform, with a detailed description on the optimizations used for the two instruments.

FSSCAT is an innovative mission concept consisting of two federated 6U Cubesats in support of the Copernicus Land and Marine Environment services. The first CubeSat carries the Flexible Microwave Payload-2 (FMPL-2), a dual microwave payload (a GNSS-Reflectometer and an L-band radiometer with interference detection/mitigation), and the second one a hyper-spectral optical payload. The combined use of these payloads will allow to measure soil moisture, ice extent, and ice thickness, and to detect melting ponds over ice. FSSCAT also includes radio and optical inter-satellite links to test some of the techniques and technologies for the upcoming satellite federations. FSSCAT will be the precursor of a constellation of federated small satellites for Earth observation achieving high temporal resolution and moderate spatial resolution in a cost-effective manner.

During these years, novel Distributed Satellite Systems (DSS) have disrupted traditional space segment paradigms. In particular, Federated Satellite Systems and fractionated spacecraft have explored the benefits of interacting satellite networks and are envisioned to improve Earth observation performance while maximizing mission utility. Inter-Satellite Communications capabilities and spacecraft coordination mechanisms are cornerstone aspects that need be designed and evaluated to achieve many of the envisioned DSS characteristics (e.g. in-orbit data services, autonomous mission planning). Given the system complexity, heterogeneity and large-scale, the design of these critical features has to be grounded on simulation-based frameworks. Consequently, this paper presents the design of a highly modular and reconfigurable software that enables the emulation of DSS. The paper motivates the design and discusses its adaptability to future user needs.