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Thermal knife HDRMs (Hold Down and Release Mechanisms) are commonly used in CubeSats and other small satellites. However, detailed information on proven designs is difficult to find. Design of a robust and reliable mechanism can present technical challenges which may only become apparent during testing, and often only when tested in a space representative environment. A custom thermal knife HDRM was designed and built for the antenna deployment module of EIRSAT-1 to deploy four coil spring antenna elements, but the same or a similar design could be repurposed quite easily to release a wide range of CubeSat deployables. In this design resistors are used to cut dyneema lines. For robustness and reliability, the thermal response of the mechanism must be well understood. To reach the melting point of the dyneema (150C) the power dissipated in the resistors must often exceed the maximum rated value. Therefore, choosing the operating current and the burn time is a careful trade-off between ensuring that the resistor reliably cuts the dyneema line and ensuring that the resistor, solder joints, PCB and nearby components are not damaged by the high temperatures. These choices are further complicated by the requirement that the mechanism operates over a range of temperatures. A thermal vacuum test campaign was carried out to better understand and characterise the thermal behaviour of the EIRSAT-1 mechanism. For the test a model of the mechanism was built with several temperature sensors installed. Two of these sensors were installed directly on the body of the resistors using a thermally conductive epoxy. Burn tests were performed in vacuum at temperatures between -37C and +56C. The test shows many interesting results including the effect of the dyneema lines on the thermal response, the possibility of desoldering the burn resistors and a comparison between the performance at ambient and vacuum conditions. Finally, a summary is given of the key technical challenges associated with this type of mechanism along with some recommendations to help make future designs more robust and reliable.

The Remote sensing and Interference detector with radiomeTry and vegetation Analysis (RITA) is one of the Remote Sensing payloads selected as winners of the 2nd GRSS Student Grand Challenge in 2019, to fly on board of the 3U AlainSat-1. This CubeSat is being developed by the National Space Science and Technology Center (NSSTC), United Arab Emirates University. RITA has been designed as an academic mission, which brings together students from different backgrounds in a joint effort to apply very distinct sensors in an Earth Observation mission, fusing their results to obtain higher-accuracy measurements. The main payload used in RITA is a Total Power Radiometer such as the one on board the FSSCat mission. With these radiometric measurements, soil moisture and ice thickness will be obtained. To better characterize the extensive Radio-Frequency Interferences received by EO satellites in protected bands, several RFI Detection and Classification algorithms will be included to generate a worldwide map of RFI. As a novel addition to the 3Cat family of satellites and payloads, a hyper-spectral camera with 25 bands ranging from 600 to 975 nm will be used to obtain several indexes related to vegetation. By linking these measurements with the soil moisture obtained from the MWR, pixel downscaling can be attempted. Finally, a custom- developed LoRa transceiver will be included to provide a multi-level approach to in-situ sensors: On-demand executions of the other payloads will be able to be triggered from ground sensors if necessary, as well as simple reception of other measurements that will complement the ones obtained on the satellite. The antennas for both the MWR and the LoRa experiments have been developed in-house, and will span the entirety of one of the 3U sides of the satellite. In this work, the latest development advances will be presented, together with an updated system overview and information about the operations that will be conducted. Results obtained from the test campaign are also presented in the conference.

Thanks to the advances in the miniaturization and improved power consumption efficiency of electronics, computers, cell phone technologies, etc., today’s spacecrafts and payloads are reducing their size and increasing their performance. However, not all systems can be reduced, as their dimensions are determined by the laws of physics. This study is focused on the design of an L-band reflector antenna for a CubeSat-based Earth observation mission devoted to measure the surface soil moisture. Two configurations of deployable parabolic reflector antennas and meshes are presented from the mechanical point of view. The electromagnetic analyses including the antenna feeder are also presented. It is found that the regular circular mesh performs slightly better than the irregular one, although requires a more careful manufacturing process. This work was supported in part by the Project “Sensing With Pioneering Opportunistic Techniques-SPOT,” Spanish Agencia Estatal de Investigación under Grant RTI2018-099008-B-C21 and EU ERDF funds, and in part by UPC-CommSensLab María de Maeztu Unit under Grant MDM-2016-0600.

Earth Observation applications are demanding higher spatial resolution and shorter revisit times than existing systems, which can be met by ad-hoc constellations of Federated Satellite Systems. These systems are distributed satellite architectures which rely on the collaboration between satellites that share unused resources, such as memory storage, computing capabilities, or downlink opportunities. In the same context, the Internet of Satellites paradigm expands the federation concept to a multi-hop scenario, without predefining a particular satellite system architecture, and deploying temporal satellite networks. The basis of both concepts is the offer of unused satellite resources as services. Therefore, it is necessary that satellites notify their availability to the other satellites that compose the system. This work presents a novel Opportunistic Service Availability Dissemination Protocol, which allows a satellite to publish an available service to be consumed by others. Details of the protocol behavior, and packet formats are presented as part of the protocol definition. The protocol has been verified in a realistic scenario composed of Earth Observation satellites, and the Telesat mega-constellation as network backbone. The achieved results demonstrate the benefits of using a protocol as the proposed one, which in some cases even doubles the amount of data that can be downloaded. To the best of our knowledge, this proposal is the first protocol that allows deploying opportunistic services for Federated Satellite Systems., This work was supported in part by the ’’CommSensLab’’ Excellence Research Unit Maria de Maeztu Ministerio de asuntos Económicos y transformación digital (MINECO) under Grant MDM-2016-0600; in part by the Spanish Ministerio de Ciencia e Innovación (MICINN) and European Union - European Regional Development Fund (EU ERDF) project ’’Sensing with pioneering opportunistic techniques‘‘ under Grant RTI2018-099008-B-C21; in part by the Agència de Gestió d’Ajuts Universitaris i de Recerca (AGAUR)—Generalitat de Catalunya (FEDER) under Grant FI-DGR 2015; and in part by the Secretaria d’Universitats i Recerca del Departament d’Empresa i Coneixement de la Generalitat de Catalunya under Grant 2017 SGR 376 and Grant 2017 SGR 219.

Global Navigation Satellite System (GNSS) receivers are the cornerstone of several modern systems: from smartphones to military applications. Therefore, their security is of utmost importance. This Master Thesis performs a security assessment on Septentrio's AsteRx-m3 receiver on two planes: a penetration testing engagement with the receiver's interfaces, and a GPS L1 C/A signal spoofing project. The assessment is satisfactory and distinct vulnerabilities are found on the web interface of the receiver, raging from low to high severity. On the GPS signal side, the Software Defined Radio used to carry out the spoofing is the HackRF One and the false GPS L1 C/A signal is generated using the software GPS-SDR-SIM. At first, the receiver detects the HackRF One signal Code-Carrier Divergence and repudiates the signal. After identifying and describing the problem, a fix is correctly implemented and, finally, the AsteRx-m3 receiver is successfully spoofed.

Initial global extremes in lightning duration and horizontal distance were established in 2017 (Lang et al. 2017) by an international panel of atmospheric lightning scientists and engineers assembled by the WMO. The subsequent launch of NOAA’s latest GOES-16/17 satellites with their Geostationary Lightning Mappers (GLMs) enabled extreme lightning to be monitored continuously over the western hemisphere up to 55° latitude for the first time. As a result, the former lightning extremes were more than doubled in 2019 to 709 km for distance and 16.730 s for duration (Peterson et al. 2020). Continued detection and analysis of lightning “megaflashes” (Sequin, 2021) has now revealed two flashes that even exceed those 2019 records. As part of the ongoing work of the WMO in detection and documentation of global weather extremes (e.g., El Fadli et al. 2013; Merlone et al. 2010), an international WMO evaluation committee was created to critically adjudicate these two GLM megaflash cases as new records for extreme lightning. We thank S. A. Rutledge and two other reviewers for their valuable comments. M. J. Peterson was supported by the U.S. Department of Energy through the Los Alamos National Laboratory (LANL) Laboratory Directed Research and Development (LDRD) program under project number 20200529ECR. Los Alamos National Laboratory is operated by Triad National Security, LLC, for the National Nuclear Security Administration of U.S. Department of Energy (Contract 89233218CNA000001). T. Logan supported by a NOAA Grant NA16OAR4320115 “Lightning Mapper Array Operation in Oklahoma and the Texas Gulf Coast Region to Aid Preparation for the GOES-R GLM.” I. Kolmasova was supported by GACR Grant 20-09671. S. D. Zhang was supported by a NOAA Grant NNH19ZDA001N-ESROGSS. The participation of J. Montanya in this work is supported by research Grant ESP2017-86263-C4-2-R funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe,” by the “European Union”; and Grants PID2019-109269RB-C42 funded by MCIN/AEI/10.13039/501100011033.

Throughout this study, the application of satellites in a Very Low Earth Orbit (VLEO) is analyzed to complement the already existing technologies used for vessels tracking. This study is part of the DISCOVERER project, which focuses on the research and development of VLEO technologies to apply them in Earth Observation (EO). Within the team, the UPC focuses on market analysis and the study of business opportunities for VLEO technologies. A value proposition is developed following the Canvas model, this being the strategy used to offer a service to a specific client. For the development of the value proposition, the study focuses on optimizing vessels tracking for maritime transport companies. A market study is carried out previously, to analyse how could the value proposition fit in it. The analysis determines that the optimal methodology and technologies to complement the platforms currently used for vessels tracking with an AIS system (Automatic Identification System) installed, is through Data Integration. This method refers to the combination of the data obtained by different platforms (satellites with different technologies and in different orbits complementing both, aerial and terrestrial platforms) once received in the ground station. For the tracking of those ships exempt from carrying an AIS transponder or those that do not want to be tracked, the optimal tracking method would be the combination of data between different platforms before being received on the ground station (System Integration).

Having a quality connectivity service is key in the economic, educational and health development of today’s society. However, current communication systems are not capable of providing full community connectivity, leaving the most remote areas underserved. This project analyzes how the Telesat satellite operator, through its Telesat Lightspeed constellation, proposes a business model based on deploying 298 satellites in low Earth orbits (LEO) to face the most demanding telecommunications challenges, and close the digital divide between urban and rural communities by delivering a universal, fast and affordable internet service. Therefore, studying the benefits and applications of low Earth orbits, analyzing the characteristics of Telesat and its constellation of satellites, as well as examining how it intends to carry out its value proposition and the risks it faces, are the main points on which this thesis is based.

Satellite-based, non-terrestrial networks (NTN) are crucial in providing global connectivity coverage, supporting important use cases in future 3rd Generation Partnership Project (3GPP) 6th generation networks (6G). Existing systems stand out due to their high complexity and specialized user equipment (UE) that comes with high operational costs. The rise of CubeSat and SmallSat spacecraft technology drastically cuts the cost of deployment, especially in Low Earth Orbits (LEO). Possible access architectures for NTN include repeater-like architectures with transparent payloads, where the gNB/eNB is located on the ground segment, or regenerative payloads, with a full gNB/eNB located on the satellite. A key NTN service is expected to be based on the extension of the NB-IoT (NarrowBand Internet of Things) protocol deployed over low-density LEO constellations using regenerative payloads, that are able to operate without having an active feeder link connection with a ground station. Enabling this service requires solving two key architectural challenges, namely the operation of the NB-IoT protocol in store and forward mode and supporting multi-tenancy, with multiples service providers using the same LEO constellation to extend their service footprint. The main contribution of this paper is the capacity analysis of a revised 3GPP architecture for NB-IoT services with a regenerative NTN architecture supporting discontinuous service and feeder link connectivity, by adding store and forward functionality. The assesment is supported by analysing the information flow of the revised architecture. Based on that architecture, we present a practical NB-IoT constellation and provide a capacity analysis. That constellation enabling for NB-IoT coverage across the globe may be possible with as little as one satellite, assuming its orbit covers the whole globe. Furthermore, we analyze authentication and user data transport with the maximum number of supported UE per satellite due to capacity constraints in the feeder link under typical data patterns. We find that variations in revisit and visibility times for both UEs and ground stations significantly impact the maximum number of supported users. Finally, the paper points out that new architectures for discontinuous backhauling, as one of the key NTN challenges, must be solved by future 6G networks.

Small satellites are becoming increasingly popular in several applications, in which attitude systems might require high precision performance. These spacecrafts are susceptible to magnetic disturbances in orbit, such as the interaction between the satellite and Earth’s magnetic field. However, a major disturbance torque is generated by the residual magnetic moment. Therefore, a magnetic cleanliness analysis must be considered in order to meet the requirements for magnetic-sensitive instruments and subsystems. Studies on magnetic environment management are underway for the FORESAIL-1 and FORESAIL-2 missions using the optical magnetic test bed of Aalto University. This is particularly important for FORESAIL-2 which aims to precisely measure the orbital ambient magnetic field with a high sensitivity magnetometer One of the parts of a spacecraft magnetic cleanliness analysis is the modelling of the residual magnetic moment as a set of magnetic dipoles. The dipoles are estimated from the measured magnetic field surrounded by the device-under-test (e.g., complete satellite, or its individual subsystems) using a stochastic estimation algorithm. The measurements are performed in a Helmholtz cage where the device and a low-noise magnetometer are placed, and detected by a smart camera using visual detection markers (ArUco). Information provided by the detection of the markers is then used for representing the position of the magnetometer and measured magnetic field points in the device-under-test coordinate frame. The camera detection accuracy is improved with data fusion from several ArUco markers, and the system performance is assessed by verifying the estimated magnetic moment results using known permanent magnets. Using this methodology for calculating the residual magnetic moment, the system is able to estimate the dipole’s position and magnetic vectors with a mean absolute error of 0.004 ± 9·10-7 m and 0.007 ± 1·10-4 A·m2 respectively. The test bed can be used for the characterization of the magnetic moment when measuring small satellites, or its components, in order to mitigate the residual magnetic moment.

This paper aims to facilitate getting acquainted with CubeSat preliminary design by presenting a review of open-source tools commonly used during project first steps, and a concrete example. The light but realistic preliminary design framework is based on a real 3U CubeSat use-case, the CREME project, relying on Nanospace and a package of selected Open-Source tools. This example should allow students and non-related field experts to fully grasp the concepts needed to achieve the basics of a typical preliminary design.

9 pages, 4 figures, supplementary information https://doi.org/10.1038/s41598-022-10265-1.-- This work is a contribution to CSIC PTI Teledetect, Changes in the Earth’s water cycle can be estimated by analyzing sea surface salinity. This variable reflects the balance between precipitation and evaporation over the ocean, since the upper layers of the ocean are the most sensitive to atmosphere–ocean interactions. In situ measurements lack spatial and temporal synopticity and are typically acquired at few meters below the surface. Satellite measurements, on the contrary, are synoptic, repetitive and acquired at the surface. Here we show that the satellite-derived sea surface salinity measurements evidence an intensification of the water cycle (the freshest waters become fresher and vice-versa) which is not observed at the in-situ near-surface salinity measurements. The largest positive differences between surface and near-surface salinity trends are located over regions characterized by a decrease in the mixed layer depth and the sea surface wind speed, and an increase in sea surface temperature, which is consistent with an increased stratification of the water column due to global warming. These results highlight the crucial importance of using satellites to unveil critical changes on ocean–atmosphere fluxes, This work was supported in part by the Spanish R&D project L-BAND (ESP2017-89463-C3-1-R), which is funded by MCIN/AEI/10.13039/501100011033 and “ERDF A way of making Europe”, and project INTERACT (PID2020-114623RB-C31), which is funded by MCIN/AEI/10.13039/501100011033. , and in part by the European Space Agency by means of the Contract SMOS ESL L2OS. We also acknowledge funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)

This project aims to study the quality of communication using nanosatellites in LEO orbits. The objective is to study the signal attenuation by radio frequency (RF) antennas between a nanosatellite and a ground station, or another nanosatellite. For this purpose, a MATLAB simulator is developed that allows the modeling of satellite orbits by using TLEs, orbital elements or Walker constellations. As for the communication parameters, different transmission frequencies and atmospheric propagation models can be used. As for the antennas, two different types are used: parabolic reflectors for ground stations and patch antennas for satellites. The quality of a communication link is determined by two different methods: using the received power or the signal-to-noise ratio in reception. In the case of received power, this should be higher than the sensitivity of the transceiver under study, while signal-to-noise takes into account different digital modulations that determine the probability of message loss. Thanks to this simulator, it is possible to obtain results that determine the visibility times between satellites and/or ground stations, and to determine if the communication for a given link meets the minimum communication requirements, as well as to calculate the transmission power necessary to meet these requirements. It also performs a 3D representation in which the orbits of the satellites as well as the ground stations can be observed.

Global Navigation Satellite Systems reflectometry (GNSS-R) is a particular case of a multistatic radar in which the signals transmitted by navigation satellites are the signals of opportunity. These signals can be processed as a radar scatterometer, as a radar altimeter, or as an unfocused synthetic aperture radar. GNSS-R has shown its potential to infer numerous geophysical variables: over land soil moisture, vegetation height, detection of freeze-thaw state, etc., map sea ice extent and type…, and over the ocean wind speed and direction, significant wave height, altimetric measurements or even more recently NASA has released a marine plastics litter product, and some also claim that sea surface salinity (SSS)canbeinferred.Inaddition,retrievalalgorithmsneglectsome of the variations of the delay Doppler map (DDM) that are linked to the observation geometry, i.e., look angle with respect to the speed vectors of the transmitter and receiver. All these different effects impact the DDM peak value and its shape, and may affect the retrieval of geophysical parameters, and ultimately the data interpretation. In this study, the following factors impacting the DDM peak value are studied: the observation geometry, the sea surface temperature, and SSS, the 10 m height wind speed (U10) and direction (WD), the presence of foam, the sea development state, the presence of swell, currents, rain, and the presence of oil slicks perturbing the sea surface roughness. This illustrates the complexityofthechallengespresentedwhentryingtoretrievesome of these variables, the required corrections, and their accuracy., This work was supported in part by the Programa Estatal para Impulsar la Investigación Científico-Técnica y su Transferencia, del Plan Estatal de Investigación Científica, Técnica y de Innovación 2021-2023 (Spain) under Grant PID2021-126436OB-C21, in part by the European Social Fund, and in part by the GENESIS: GNSS Environmental and Societal Missions–Subproject UPC under Grant PID2021-126436OB-C21. (Corresponding author: Adriano Camps.)

Complementing and extending the coverage reach of terrestrial networks with satellite access is one of the new connectivity frontiers being addressed on the path to beyond 5G/6G systems. In particular, the realization of almost ubiquitous connectivity in a seamless and cost-affordable manner for low-complexity, power-constrained devices is key to unleashing the potential of the massive IoT market, where the lack of global coverage and international roaming are currently standing as main limiting factors for market growth. To harness this potential, the 3rd Generation Partnership Project (3GPP), the standard development organization in charge of the mobile system specifications, is finalizing a first adaptation of the Narrowband Internet of Things (NB-IoT) protocol for non-terrestrial networks (NB-IoT NTN) as part of Release 17 specifications. This paves the way for integrated terrestrial-to-satellite connectivity solutions that could leverage and help further boost the large and growing 3GPP device and IoT application ecosystem. The NB-IoT NTN protocol is being designed to support different types of satellite deployments, including Geostationary Orbit (GEO), Medium Earth Orbit (MEO) and Low Earth Orbit (LEO) constellations, single-beam and multi-beam satellite platforms, and Earth-moving and Earth-fixed satellite cells. In this context, this paper presents a system level performance analysis of a NB-IoT NTN deployment solution using nanosatellite in sparse LEO constellations, which is one of the most challenging scenarios in terms of achievable coverage footprint and satellite capacity due to the power and size constraints in the satellite platform. A framework for modelling such scenarios is described in the paper and estimations of system performance indicators such as number of connections that can be handled simultaneously, effective satellite footprint coverage area and supported device density (UEs/km2) are provided for different representative operational configurations (e.g. multi-carrier configurations with anchor and non-anchor carriers) and traffic characteristics (e.g. application payload sizes). Our results demonstrate the technical feasibility of such a system and illustrate some of the relevant trade-offs between the system configurations and communication performance.

Objectius de Desenvolupament Sostenible::13 - Acció per al Clima Objectius de Desenvolupament Sostenible::15 - Vida d'Ecosistemes Terrestres

© 2022 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. Soil Moisture and Ocean Salinity mapping by Earth observation satellites has contributed significantly toward a better understanding of the Earth system, such as its hydrosphere or climate. Nevertheless, an increased spatial resolution below 10 km with a radiometric resolution in the range of 2 K–3 K of radiometric data could yield a more complete picture of global hydrological processes and climate change. Operational radiometers, such as SMOS, have already approached prohibitive sizes for spacecraft due to the required large antenna apertures. Therefore, radiometer concepts based on a large number of satellites flying in close proximity (swarms) have been proposed as a possible solution. This article investigates the orbit mechanics of placing a satellite swarm-based motion induced synthetic aperture radiometer (MISAR) in low Earth orbit for Earth observation applications. The aperture synthesis antenna array is formed by a large number of individual antennas on autonomously controlled nanosatellites (deputies) and a correlator antenna in the Y-configuration carried by a chief satellite. The proposed design methodology is based on the optimization of satellite positions within a plane and the subsequent translation of coordinates into initial conditions for general circular orbits (GCOs). This enables a more computationally efficient orbit optimization and ensures the time invariance of the antenna array response. Based on this methodology, simulations have been performed with swarms consisting of up to 96 satellites. Simulations show that the spatial resolution of an aperture synthesis radiometer can be increased to less than 10 km for applications where the requirements on radiometric sensitivity are more relaxed ( ΔT∼3 K).

The DISCOVERER project commenced in 2017 with the aim to advance the development of key technologies to enable the commercially viable, sustained operation of satellites in very low Earth orbits (VLEO). Funded by the European Commission through Horizon 2020, the project ends this month. This paper presents an overview of the key achievements and current status of the project. The project set out to advance the development of, and demonstrate, several technologies with the long-term aim of enabling the commercial use of VLEO. These technologies include: 1. aerodynamic materials which encourage specular scattering of the incoming flow to minimise drag and increase the performance of aerodynamic surfaces in the highly rarefied flows experienced in VLEO 2. aerodynamic attitude control methods to compensate for the dynamic flow environment, especially lower in the VLEO altitude range 3. atmosphere breathing electric propulsion (ABEP), combining an optimised atmospheric intake with advanced RF Helicon-based plasma thruster, for drag compensation DISCOVERER’s test satellite, the Satellite for Orbital Aerodynamics Research or SOAR, was deployed from the International Space Station in June 2021 and re-entered the atmosphere in March 2022. The primary aim was to measure the induced drag and lift on different aerodynamic materials candidates in VLEO by exposing panels, coated in various novel and control materials, to the flow at different orientations whilst observing the induced attitude and orbit perturbations produced. Early analysis of the results from the mission shows promising results for the novel materials developed as part of the project. Parallel studies on the long-term survivability of these materials to the space environment have been on-going through exposure tests on the exterior of the International Space Station through the MISSE programme. The project has also been developing a ground-based facility, the Rarefied Orbital Aerodynamics Research facility, to characterise the gas surface interaction properties of materials to atomic oxygen at orbital velocities. Characterisation of the facility itself is on-going. In support of ABEP technology, the experimental development and characterisation of an RF Helicon-based plasma thruster has been on-going, along with detailed computational modelling of aerodynamic intakes. Whilst the thruster has already been operated, current work focusses on the characterisation of its performance. Finally, work to place these technological developments into context has also been progressed. On overview of the overall achievements in this area is provided, including business modelling of the VLEO market ecosystem, which identifies the enormous market potential for VLEO missions. Peer Reviewed Article signat per 30 autors: Peter C.E. Roberts, Nicholas H. Crisp, Steve Edmondson, Antonio Arcos, Georg H. Herdrich, Jonathan Skalden, Silvia Rodriguez-Donaire, Daniel Garcia-Almiñana, Alejandro Macario-Rojas, Katharine L. Smith, Ciara Mcgrath, Sarah J. Haigh, Vitor T.A. Oiko, Brandon E.A. Holmes, Luciana A. Sinpetru, Virginia Hanessian, Simon Christensen, Thomas Kauffman Jensen, Jens Nielsen, Morten Bisgaard, Francesco Romano, Stefanos Fasoulas, Constantin Traub, Konstantinos Papvramidis, Miquel Sureda, Dhiren Kataria, Badia Belkouchi, Alexis Conte, Simon Seminari, Rachel Villain

Recent advancements in gamma-ray detector technology have brought new opportunities to study gamma-ray bursts and other high-energy phenomena. However, there is a lack of dissemination on the development methods, tools and techniques used in the production of instrument flight firmware. This is understandable as firmware for spacecraft payloads may be proprietary or exceptionally hardware specific and so is not always published. However, this leaves a gap in the knowledge for CubeSat teams, especially those consisting of university students who may be building a custom spacecraft payload with limited initial experience. The Gamma-Ray Module (GMOD) on-board EIRSAT-1, a 2U CubeSat in the 2nd European Space Agency Fly Your Satellite! programme, is one such instrument. GMOD features a 25x25x40mm Scionix CeBr3 scintillator, coupled to an array of 16 (4x4) JSeries OnSemiconductor MicroFJ-60035-TSV silicon photomultipliers (SiPMs) with readout provided by the SIPHRA IDE3380 application specific integrated circuit. The instrument is supported by the Gamma-Ray Module motherboard which controls and configures the instrument, providing regulated voltage and current sources as well as generating time tagged event packets and a temporary on-board flash storage. At the core of this system is the Texas Instruments MSP430FR5994 microcontroller. A custom firmware was produced for the instrument by the EIRSAT-1 team over numerous cycles of testing and development to reliably perform the long duration tasks of readout, storage and transfer of time tagged event data to the EIRSAT-1 on-board computer. Recognising the value of sharing our experiences and pitfalls on firmware development with the wider CubeSat community, this paper will provide an introduction to GMOD, with focus primarily on the development approach of the firmware. The development, testing, version control, essential tools and an overview of how the resources provided by the device manufacturer were used will be examined, such that the lessons learned may be extended to other payloads from student-led missions

This final degree thesis aims at developing a Fresnel zone plate antenna with its deployment subsystem of a GNSS-RO payload. It will be integrated in the 3Cat8 nanosatellite, one of UPC NanoSat Labs mission. This thesis embarks in several designs of the antenna as its deployments system inside the limitations the environment of outer space and other impediments of the mission At the end of this work, several promising designs pave a road for the continuation of the development of the antenna and its deployment system. After testing and analyzing the materials and design, the optimal characteristics and best designs are a starting point for the continuation of its development.

The Global Satellite Tracking Initiative aims to support international students and young professionals to set up ground stations to download real-time data and images from satellites orbiting above their regions. The objective is to empower and build capabilities among space enthusiasts around the world and to promote the space sector through hands-on activities and real space technologies related to satellite communications. The Space Generation Advisory Council, together with SatNOGS as an integral part of the Libre Space Foundation, have been supporting the initiative to enhance the development of a global open source network of satellite ground stations. The initiative will be providing all the resources, hardware, and know-how that is needed to set up ground stations. A competition was launched by the end of 2021 to select teams of space enthusiasts and supply them with a kit and step-by-step instructions on how to build their own ground stations. By setting up ground stations in backyards, local universities, or maker clubs, teams are not only self-learning about telecommunications and satellite technologies, but they are creating a meaningful impact in their local communities by bringing the broad society closer to science, technology, engineering, mathematics and, in particular, space. The initiative also intends to support space missions while engaging local communities from different regions around the world in the space sector through appealing imagery and tools. After closing the Call for Applications in this pilot initiative, 10 winning teams were selected upon receiving almost 200 applications from more than 60 countries. The selected winners are based in the following emerging space faring nations: Benin, Bolivia, Egypt, Ethiopia, Nepal, Peru, Philippines, Rwanda, Vietnam, and Zimbabwe. They are being supplied with a basic Ground Station Kit and instructions on how to receive live images and data from different space missions, starting with the following frequency bands: - 137 megahertz: To receive images from National Oceanic & Atmospheric Administration satellites. - 144-146 megahertz: To receive images and data from the International Space Station. - 440 megahertz: To receive data from numerous scientific and educational small satellites. Those teams that manage to set up the basic ground station kits and conduct some outreach and educational activities will receive a more advanced system. This paper captures the process to be followed by the selected teams, from the unboxing of the hardware to the reception and processing of data from operational space missions.

Earth Observation satellite missions can provide global and frequent coverage. In the past decade we have seen an explosion of these missions based on three unit CubeSats, notably with Planet and Spire constellations of visible and near-infrared imagers and GNSS-Radio Occultations payloads. One of the most important parts of these type of payloads is the antenna, which is limited due to the dimensions of the CubeSats. Today, the largest deployable antenna for CubeSats has a diameter of 50 cm and it was part of RainCube rain radar. ESA is currently sponsoring two studies to develop a 1 m deployable reflector antenna for CubeSats. Although the most common solutions are the deployable reflectors, Fresnel Zone Plate antennas are a simple type of antennas that can overcome some of the technical limitations of these reflectors. In this paper we will present the design and tests of a deployable Fresnel Zone Plate antenna with 155 cm diameter, at a distance of 58 cm from the feeder. During the design, the modularity of the system has been considered, so that other antenna types can also be deployed. This antenna has a triangular shape, and each end is attached to a telescopic carbon fiber rod, which is deployed by means of a toothed belt that pushes them from its inner part. Each toothed belt is pushed with a DC motor. If accepted for a launch of opportunity, this antenna will be used in a GNSS-Radio Occultations payload onboard 3Cat-8, one of the future satellite missions of the UPC NanoSat Lab

The LEDSAT 1U Cubesat, a satellite roughly 10x10x11cm, was developed between late 2016 and 2021 by students of Sapienza University of Rome. The project was conceived with the help of the University of Michigan and started being developed by space engineering master students of Sapienza in a class context. The team of the S5Lab (Sapienza Space System and Space Surveillance Laboratory) continued the project and applied for the Fly Your Satellite! Programme of ESA Education, which has followed the development of the CubeSat, providing important expert support and periodic reviews. The approach brought to the students an invaluable educational experience as they participated actively in the development of a spacecraft with the typical milestones of satellite projects. The mission objectives of LEDSAT include the use of onboard LEDs for improved orbit determination, experimental attitude determination and backup light communication. Each of the six sides of the CubeSat houses an LED board of a different color (red, green, and blue) with opposite sides with paired color. The LEDs can flash a pattern predefined by radio telecommand and the light is observed using ground telescopes. The design of the spacecraft started in late 2016 and was presented at the selection workshop of the Fly Your Satellite! Programme in May 2017. Final assembly took place in mid-2020 after which the team performed functional and environmental testing between October and December 2020, with the objective of ensuring the survivability of the spacecraft in the space environment and characterization of its behavior. After successful testing, the spacecraft was integrated inside the deployer in July 2021 in Brno, Czech Republic and was launched from Kourou, French Guiana on August 17th, 2021, aboard the Vega VV19 launcher. The spacecraft is now in orbit and operating nominally, with the LED flashes having been observed several times. The development of the spacecraft was not without difficulty, with preventable issues arising through testing that imposed design changes and further analysis - the paper will walk through the project since its conception, throughout the development, the functional and environmental testing of the payload and at system level, emphasizing the lessons learned by the students.

The Satellite for Orbital Aerodynamics Research (SOAR) is a 3U CubeSat that has been designed to investigate the aerodynamic performance of different materials and perform demonstrations of aerodynamic attitude control manoeuvres in very low Earth orbit (VLEO). SOAR was deployed from the ISS on 14th June 2021 into a naturally decaying orbit and deorbited on 14th March 2022. This paper provides an overview of the operations performed during the mission and presents preliminary experimental results obtained from this spacecraft. SOAR was designed and launched within the frame of DISCOVERER, a Horizon 2020 project that aimed to support the development of a new class of commercially viable spacecraft operating in VLEO, i.e., orbits below 450 km in altitude. Operating in these lower altitude orbits has several benefits to the design of spacecraft, particularly for Earth observation and communications applications. However, development of spacecraft that can operate sustainably at these altitudes requires advancement in foundational technologies, for example atmosphere-breathing electric propulsion (ABEP) and novel aerodynamic materials. The primary aim of SOAR was to characterise the aerodynamic performance of different materials at very low altitudes and accomplished this task using a set of steerable fins that exposed different materials to the oncoming flow and an ion and neutral mass spectrometer (INMS) to provide in-situ measurements of atmospheric properties. SOAR was also designed to perform novel aerodynamic attitude control manoeuvres and measurements of thermospheric winds. Two of the materials carried to orbit were selected for their atomic oxygen erosion resistance and potential improvement in aerodynamic performance. The identification of such materials would allow for a reduction in the drag experienced in VLEO, the design of atmospheric intakes with greater efficiency used for ABEP, and implementation of enhanced aerodynamic attitude and orbit control. Ongoing ground-based experimentation seeks to further characterise the properties of such materials and to deepen our understanding of the physical interaction mechanisms that occur in the rarefied flow environment of VLEO.

The ESA ESEO Mission [1] included an amateur radio payload [2]. The results of which included the development of radio technologies that utilised final year student projects over a 5 year period. Many lessons regarding compliance and process enabled a new payload to follow: the Student Ranging Transponder Radio for X-band and L-band (or STAR-XL). The STAR-XL design leverages key aspects of the ESEO payload design for a generic CubeSat platform; including TT&C voltage and current sense circuitry, receiver circuitry, and flight software. But instead of a maximum 4800 bps telemetry and transponder system - the STAR- XL targets a 100 kHz bandwidth system that will allow faster downlink rates that are forward error correction, link margin and modulation order dependent. With 100 kHz bandwidth, the linear receiver is designed to also operate as a transponder - enabling ranging and navigation applications such as orbit determination and further experiments from amateur radio groundstations. This paper details the recent student project efforts in three key areas: a new STM32-based on-board computer, an X-band up-converter board and dual X/L band patch (as shown in Fig. 1). The new OBC includes an IQ modulator for transmitting complex waveforms and an optimised flight software suite that takes advantage of dual DMA hardware on-chip to reduce overheads. The X-band upconverter board required the development of new safety interlock and RF chain circuitry on a Rogers (RO4350B) PCB material. A new dual X/L-band patch antenna and filter circuit is also built and measured. Each of these projects has led to new lessons and increased the real-world case studies used to teach spacecraft avionics.

Very Low Earth Orbits (VLEOs), those below 450 km, present a number of benefits and challenges for the development and operation of Earth observation spacecraft at both the system and mission level. This paper examines the design of constellations of satellites for operation in VLEO for Earth observation considering both system and mission level trade-offs. The resulting analysis identifies general design trends and proposes suitable mission architectures for Earth observation from VLEO. The principal benefit for satellites operating in VLEO is that the reduction in the distance to the Earth’s surface allows better imaging resolution to be achieved using smaller and less powerful payloads. This has corresponding benefits for the system mass and cost. However, the sustained and controlled operation of spacecraft in VLEO is challenging due to the increased atmospheric density at these altitudes, which increases propulsive and attitude control requirements. Technologies to facilitate the commercially viable operation of spacecraft in VLEO are currently being developed, for example materials to facilitate drag-reduction and aerodynamic control and atmosphere-breathing electric propulsion systems (ABEP), each of which influence the design of other sub-systems, requiring, for example, varying levels of power or new geometric considerations. At the mission level, the reduction in altitude has a generally negative influence on the coverage and revisit characteristics of a given satellite. However, deployment of these satellites in constellations can provide improvements in the overall system metrics. Systems operating in VLEO may also benefit from improved launch vehicle capability and assured end-of-life deorbit. It is clear, therefore, that important and non-intuitive trade-offs between the satellite platform design, constellation configuration, and total cost arise in the design of these systems. This paper uses combined platform-level system modelling and mission analysis to explore the design of constellations of satellites in VLEO for Earth observation and demonstrates the necessity of a holistic approach to mission and system design when considering operations in VLEO.

Unmanned aerial vehicles (UAVs) are widely deployed in air navigation, where numerous applications use them for safety-of-life and positioning, navigation, and timing tasks. Consequently, GPS spoofing attacks are more and more frequent. The aim of this work is to enhance GPS systems of UAVs, by providing the ability of detecting and preventing spoofing attacks. The proposed solution is based on a multilayer perceptron neural network, which processes the flight parameters and the GPS signals to generate alarms signalling GPS spoofing attacks. The obtained accuracy lies between 83.23% for TEXBAT dataset and 99.93% for MAVLINK dataset. This work was supported in part by the Catalan Government, through the program 2017-SGR-962 and the RIS3CAT DRAC project 001-P-001723, and by the EPFL, Switzerland.

Communication links over satellites allow interconnecting very distant regions to provide service where the terrestrial networks are limited. In this scenario, it is of major importance to devise mechanisms accounting for the improved freshness of packets given the impact of large distances. Their analysis is particularly important when considering the deployment of sensors in remote areas, where satellite links may introduce a high delay in the communication system. In this respect, we report the use of age of information (AoI) metrics to evaluate users' allocation mechanisms. We use power-domain non-orthogonal multiple access (NOMA) as an alternative to orthogonal multiple access (OMA) to optimally reduce the age of received packets. We derive the proper formulation to account for a fairness condition when pairing users accounting for both; the user's needs to transmit information and the allowable link rate. Comparative results are provided by numerically evaluating the solution for NOMA and OMA accounting for the peak age of information (PAoI) metric. We show that the resource allocation mechanisms in NOMA results in less PAoI (40%) compared to OMA. We remark this result through extensive numerical simulations based on actual uplink satellite communication links accounting for 500 users. This work has been supported by the Spanish National Project IRENE (PID2020-115323RB-C31, PID2020- 115323RB-C33 / AEI / 10.13039/501100011033).

This article presents the QuantSaT-PT project, an effort to create the first Portuguese nanosatellite for space to ground quantum communication. Focused on the Attitude Determination and Control System, it describes the different elements that allow for the attainment of diverse accuracy levels required for separate mission stages. Given the harsh pointing precision necessary for establishing a quantum downlink, the implementation of this module presents a major challenge in the Cubesat field. Furthermore, the introduced architecture aims to reduce system cost by replacing the state-of-the-art star tracker with ground beacon detection.

A Mach contest is part of an annual event, organized by UKLSL, which combines both CanSat and rocket competitions. The first Mach event in 2021 was focused on the design of “Simple and Advance CanSats”, and culminated on a 3-day activity at Machrihanish Airbase in Scotland. It involved setup, pre-flight checks, and system adjustments. This paper focuses on the design challenges, and outcomes from building a satellite the size of a soda can by reviewing the event, the mission designed for the competition, and students’ feedback on what could have been improved to prepare the next team competing in Mach-22 which would involve developing a Rocket design and launching an “Advance CanSat”. The competition allowed undergraduate students at The University of Nottingham to experience a practical learning style by solving real engineering problems and practicing professional development skills through design review presentations and providing a flight readiness review to the launch providers of the competition. The proposed mission statement was part of the “PEAK” category, which involved atmospheric studies, where it acts as a simulation model for measuring the atmosphere on different planets and as a deployable probe from rovers to measure varying atmospheric levels. The competition exposed students to perform AITV (Assembly, Integration, Testing, Verification) processes to their CanSat and constructed procedures to test and validate the recovery system. Results from the first Mach event prove a solid starting point for future CanSat competition and space activities within our university. In the future, there are aspirations to grow a student space society and get students involved in extra-curricular STEM (Science, Technology, Engineering, Math) projects, and allow them to apply the theory and concepts learned in their academics

This work aims at studying the mechanical behaviour of nano- and pico-satellites, with CubeSats and PocketQubes as the references, and designing and producing a deployment system for PocketQubes, to be integrated in a CubeSat platform. Through this project, the 3Cat-4 spacecraft will be analysied in order to assess the impact of changes made to its architecture, both at system and subsystem level, and the results evaluation will aid in decision making regarding modifications of the mechanical components. The analyses will serve as the reference for the mechanical testing during the Environmental Test Campaign (ETC). Additionally, the response of the spacecraft against the different vibro-acoustic and mechanical loads will serve as the starting point for the design of a PocketQube P-POD (Poly-Picosatellite Orbital Deployer), which will be a major subsystem integrated in 3Cat-8, a new mission of the NanoSat Lab currently in Phase B.

The Nanosatellite and Payload Laboratory (UPC NanoSat Lab) is a cross-departmental initiative belonging to the Barcelona School of Telecommunications Engineering. Its main activity is the development and design of nano-satellite missions, with its focus on the exploration of innovative small spacecraft system concepts and developing and integrating subsystems and payloads for Earth Observation. The laboratory is currently developing the 'Remote Sensing and Interference Detector with Radiometry and Vegetation Analysis', also known as RITA Payload, which is one of the Remote Sensing payloads that was selected by the second GRSS Student Grand Challenge in 2019 to fly on board of the AlainSat-1. This Payload is being developed under the supervision of the IEEE GRSS. This thesis aims to contribute to the development of the RITA mission with the design and implementation of the payload's S-Band communications. It begins with a study of satellite communications and particularly S-Band, focusing on its usefulness in the downlink of scientific results. Moreover, it presents a study of the communications scenario containing orbital simulations as well as a link budget, providing crucial information for the system's design and decisive in establishing the necessary requirements. The standards used by the European Space Agency for its missions are evaluated for their viability in this mission, with the boundary conditions that apply to them. Thus, a variation of traditional communication schemes is developed for the RITA mission, and the design process is explained in detail. The main core of the thesis consists of the implementation and design of the system. This is been split into three main sections, the application layer, the channel coding and the physical layer. On the one hand, the application layer includes the necessary protocols, frame design and systems to transform files into packets to be sent, and on the other way around, to recover files from a number of packets. On the other hand, channel coding includes all the coding and decoding systems to ensure that the system is able to recover the initial data if errors occur in the physical channel of the transmission and reception. Finally, the physical layer includes the transmission of symbols and the reception of signals, together with the necessary signal processing techniques to ensure the initially transmitted frames can be recovered correctly even if deep fading¿s or Doppler shifts have affected the received system. The thesis also presents several tests that verify the correct functioning of the system using two ADALM-PLUTO SDR devices, representative of the hardware that will be used in the satellite, to work as transmitter and receiver. The thesis concludes with a verification of the system, commenting on the difficulties and problems that have arisen during its development, and the work that should be carried out before the launch.

6G and beyond networks will merge communication and computation capabilities in order to adapt to changes. As they will consist of many sensors gathering information from its environment, new schemes for managing these large amounts of data are needed. For this purpose, we review Over the Air (OTA) computing in the context of estimation and detection. For distributed scenarios, such as a Wireless Sensor Network, it has been proven that a separation theorem does not necessarily hold, whereas analog schemes may outperform digital designs. We outline existing gaps in the literature, evincing that current state of the art requires a theoretical framework based on analog and hybrid digital-analog schemes that will boost the evolution of OTA computing. Furthermore, we motivate the development of 3D networks based on OTA schemes, where satellites function as sensors. We discuss its integration within the satellite segment, delineate current challenges and present a variety of use cases that benefit from OTA computing in 3D networks., Paper accepted in 2022 IEEE 21st Mediterranean Electrotechnical Conference (MELECON)

The Galileo High Accuracy Service (HAS) is a new capability of the European Global Navigation Satellite System that is currently under development. The Galileo HAS will start providing satellite orbit and clock corrections (i.e. non-dispersive effects) and soon it will also correct dispersive effects such as inter-frequency biases and, in its full capability, ionospheric delay. We analyse here an ionospheric correction system based on the fast precise point positioning (Fast-PPP) and its potential application to the Galileo HAS. The aim of this contribution is to present some recent upgrades to the Fast-PPP model, with the emphasis on the model geometry and the data used. The results show the benefits of integer ambiguity resolution to obtain unambiguous carrier phase measurements as input to compute the Fast-PPP model. Seven permanent stations are used to assess the errors of the Fast-PPP ionospheric corrections, with baseline distances ranging from 100 to 1000 km from the reference receivers used to compute the Fast-PPP corrections. The 99% of the GPS and Galileo errors in well-sounded areas and in mid-latitude stations are below one total electron content unit. In addition, large errors are bounded by the error prediction of the Fast-PPP model, in the form of the variance of the estimation of the ionospheric corrections. Therefore, we conclude that Fast-PPP is able to provide ionospheric corrections with the required ionospheric accuracy, and realistic confidence bounds, for the Galileo HAS. Open Access funding provided thanks to the CRUECSIC agreement with Springer Nature. The present work was supported in part by the European Space Agency contract IONO4HAS 4000128823/19/NL/AS, by the project RTI2018-094295-B-I00 funded by the MCIN/AEI 10.13039/501100011033 which is co-founded by the FEDER programme and by the Horizon 2020 Marie Skłodowska-Curie Individual Global Fellowship 797461 NAVSCIN.

The mobile communications sector has seen tremendous growth in recent years which has led to a huge demand for mobile data. This demand will require new technologies that can offer the sufficient capacity that the sector will need. One of these technologies is 5G that will improve positioning, with centimeter precision. First of all, the channel in the millimeter wave band is explained as the channel model used. The algorithm used to position and how it makes use of the channel sparsity is also explained. Afterwards, it is shown that the performance of the algorithm is good and comparing with the results obtained in the studied algorithm, it is observed that the effect of the reflections does not improve the positioning error. Likewise, it can be seen that the use of a more "realistic" simulator makes the error somewhat greater than for the case studied. Finally, the conclusions we have reached and some fields or improvements that can be implemented or investigated in the near future are explained. El sector de les comunicacions mòbils ha tingut un gran creixement durante els darrers anys que ha portat a una gran demanda de dades mòbils. Aquesta demanda requerirà de noves tecnologies que oferiran la capacitat suficient que el sector necessitarà. Una d'aquestes tecnologies és el 5G que millorarà el posicionament, amb 1 precisions de centímetres. Per començar, s'explica el canal a la banda de les ones mil·limètriques com el model de canal utilitzat. També s'explica l'algoritme utilitzat per a posicionar i com fa ús de la sparsity del canal. Després és demostra que el rendiment de l'algoritme és bo i comparant amb els resultats obtinguts en l'algoritme estudiat s'observa que l'efecte de les reflexions no millora l'error de posicionament. També es pot veure que l'ús d'un simulador més "realista" fa que l'error que es comet és més gran que pel cas estudiat Per acabar s'explica les conclusions a les que hem arribat i uns quants camps o millores que es poden implementar o investigar en un futur proper. El sector de las comunicaciones móviles ha tenido un gran crecimiento durante los últimos años que ha llevado a una gran demanda de datos móviles. Esta demanda requerirá de nuevas tecnologías que puedan ofrecer la capacidad suficiente que el sector necesitará. Una de estas tecnologías es el 5G que mejorará el posicionamiento, con una precisión de centímetros. Para empezar, se explica el canal en la banda de las ondas milimétricas como el modelo de canal utilizado. También se explica el algoritmo utilizado para posicionar y como hace uso de la sparsity del canal. Después se demuestra que el rendimiento del algoritmo es bueno y comparando con los resultados obtenidos en el algoritmo estudiado se observa que el efecto de las reflexiones no mejora el error de posicionamiento. Asimismo, se puede ver que el uso de un simulador más "realista" hace que el error cometido sea algo mayor que para el caso estudiado. Para acabar se explica las conclusiones a las que hemos llegado y algunos campos o mejoras que se pueden implementar o investigar en un futuro próximo.

Next-generation satellite systems require more flexibility in resource management such that available radio resources can be dynamically allocated to meet time-varying and non-uniform traffic demands. Considering potential benefits of beam hopping (BH) and non-orthogonal multiple access (NOMA), we exploit the time-domain flexibility in multi-beam satellite systems by optimizing BH design, and enhance the power-domain flexibility via NOMA. In this paper, we investigate the synergy and mutual influence of beam hopping and NOMA. We jointly optimize power allocation, beam scheduling, and terminal-timeslot assignment to minimize the gap between requested traffic demand and offered capacity. In the solution development, we formally prove the NP-hardness of the optimization problem. Next, we develop a bounding scheme to tightly gauge the global optimum and propose a suboptimal algorithm to enable efficient resource assignment. Numerical results demonstrate the benefits of combining NOMA and BH, and validate the superiority of the proposed BH-NOMA schemes over benchmarks. This work was supported in part by the Luxembourg National Research Fund (FNR) CORE projects ROSETTA (under grant C17/IS/11632107) and FlexSAT (under grant C19/IS/13696663).

Altimetric performance of Global Navigation Satellite System-Reflectometry (GNSS-R) instruments depends on receiver’s bandwidth and signal-to-noise ratio (SNR). The altimetric delay is usually computed from the time difference between the peak of the direct signal waveform and the maximum of the derivative of the reflected signal waveform. Dual-frequency data gathered by the airborne Microwave Interferometric Reflectometer (MIR) in the Bass Strait, between Australia and Tasmania, suggest that this approach is only valid for flat surfaces and large bandwidth receivers. This work analyses different methods to compute the altimetric observables using GNSS-R. A proposed novel method, the Peak-to-Minimum of the 3rd Derivative (P-Min3D) for narrow-band codes (e.g., L1 C/A), and the Peak-to-Half Power (P-HP) for large bandwidth codes (e.g., L5 or E5a codes) show improved performance when using real data. Both methods are also compared to the Peak-to-Peak (P-P) and Peak-to-Maximum of the 1st Derivative (P-Max1D) methods. The key difference between these methods is the determination of the delay position in the reflected signal waveform in order to compute the altimetric observable. Airborne experimental results comparing the different methods, bands and GNSS-R processing techniques show that centimeter level accuracy can be achieved., This work was funded by the Spanish Ministry of Science, Innovation and Universities, “Sensing with Pioneering Opportunistic Techniques”, grant RTI2018-099008-B-C21/AEI/10.13039/ 501100011033, and the grant for recruitment of early-stage research staff FI-DGR 2015 of the AGAUR—Generalitat de Catalunya (FEDER), Spain, and the grant for recruitment of early-stage research staff FI 2018 of the AGAUR—Generalitat de Catalunya (FEDER), Spain, and Unidad de Excelencia María de Maeztu MDM-2016-060.

Els dispositius IoT son cada vegada mes utilitzats en una gran varietat d’aplicacions, des de dotar de connectivitat a una rentadora fins a permetre el rastreig de vacunes. La majoria d’aquestes aplicacions són en entorns urbans on hi ha bona connectivitat, però algunes d’aquestes requereixen de connectivitat en llocs on no hi arriba la xarxa convencional. Aquestes aplicacions utilitzen dispositius de comunicació satel·lital, ja que poden transmetre dades des de qualsevol lloc, a costa d’uns elevats preus de transmissió i d’un major consum d’energia. El present TFG té com a objectiu el disseny, fabricació i programació d'un dispositiu electrònic que combini la tecnologia IoT tradicional amb la satel·lital, per poder transmetre la geolocalització així com altres dades que vagi adquirint el mòdul. El dispositiu ha de ser de petites dimensions i tenir una gran autonomia que permeti estar llargs períodes sense rebre cap tipus de recarrega. Per millorar l’experiència d’usuari i que aquest no haguí d’accedir a les diferents plataformes per visualitzar les dades, es dissenyarà i programa una plataforma web que recol·lecti i mostri les dades transmeses pel dispositiu de forma clara i senzilla. Nowadays the IoT devices are even more used in a large variety of applications, from equipping the washing machine with internet, to allow the tracking of the vaccines since their exit of the fabric to the use of it. Most of these applications are set in urban environments where they have a good connectivity, but some of these require connectivity in places where the common network does not reach. These applications use satellite communication devices, because these can transmit data from any place, at the expense of higher transmissions prices and more power consumption. This final degree project aims to design, build and programme an electronic device that combines the traditional IoT technology with the satellite technology, in order to send the location and other data that the device has acquired. It must be small and to have a great autonomy that permits to stay for a long time without receiving any type of recharge. To improve the user experience, for no need to access the different platforms to visualise the data, a website will be designed and programmed in order to collect and show what the device has transmitted in a clear and simple way.

The lower thermosphere (between 100 and 550 km of height) is known with lesser accuracy than desired. The use of spherical satellites to determine the density could result in a substantial improvement of the present situation. The orbits of satellites at these heights are affected by drag and the inhomogeneities of the terrestrial gravitational potential (among other perturbations). This projects has as main goal to analyse how the atmospheric drag affects the orbit of a real satellite, and then, determine the thermospheric density. Hence, it will be necessary to reconstruct the orbit accounting for the perturbations in the most accurate way possible. Regarding the gravitational potential of the Earth, we have employed three approximations: spherical symmetry, a zonal model truncated at sixth order and a tesseral model truncated at tenth order. This last model has revealed as the most accurate. To achieve our goal, we have analysed the telemetry gathered by one of the satellites of the FSSCat mission. Then, we have determined its orbital elements. Afterwards, we have considered two possible methods for orbit reconstruction: Non-Linear Least Squares and Extended Kalman Filter. After this analysis, we have chosen the Non-Linear Least Squares method for the purpose of orbit reconstruction. The orbital elements determined from a physical analysis of the telemetry and the ones resulting from the non-linear least square method coincide with a remarkable accuracy.

Objectius de Desenvolupament Sostenible::13 - Acció per al Clima

El proyecto PLATHON (PLATaforma integrada de simulación Hardware-in-the loop para comunicaciones Opticas en Nanosatélites) se plantea mediante la colaboración estudiantil en forma de Trabajos de Fin de Grado a lo largo de los años. En este trabajo, aprovechando la tarea llevada a cabo por otros proyectistas anteriormente, se diseña, monta y prueba una placa de control de actitud en dos dimensiones para un CubeSat. Esta placa está integrada por un microcontrolador, una IMU, un driver de motor, un módulo Bluetooth, una rueda de inercia, y dos magnetopares. Este proyecto en concreto se centra en el campo de los magnetopares. Para ello, se realiza el testeo de los distintos componentes por separado y posteriormente en conjunto. Se dedica también parte del tiempo a la confección de los magnetopares, al código bajo el cual se rige y visualiza el comportamiento del sistema, y por último, al diseño e implementación de un código de control detumbling

The boom of the New Space sector has been mainly influenced by one concept: the CubeSat standard. The use of this standard has increased the COTS products utilization. Therefore, the components¿ testing has become paramount for the success of a satellite mission. This project aims at studying the thermal procedures required for ensuring the correct thermal health of two satellite missions developed by UPC NanoSat Lab: 3Cat4 and RITA Payload. The study starts with the design and the execution of thermal simulations performed on RITA Payload using the Thermal Desktop software. After the simulations, the study of the procedures and specifications required for executing an Environmental Test Campaign on the RITA Payload hyper-spectral camera is conducted. As for the 3Cat4 mission, a thorough evaluation about the Electrical Power Subsystem (EPS) has been conducted. The analysis starts by delving into the EPS Engineering Model, studying the communication protocols required for connecting the subsystem to the On-Board Computer (OBC), and it continues with a characterization and verification of the subsystem¿s thermal performance along with the issues that are detected throughout the whole study, being the most important issue the loading effect detected when charging the EPS. The analysis continues with the EPS Proto-Flight Model (PFM), comparing its behaviour with the previous model and analysing additional parts of the subsystem, as though the heater. Once a specific subsystem is analysed, the study of the procedures and specifications required for executing an Environmental Test Campaign for the whole 3Cat4 satellite is performed. Finally, the general conclusions are provided. In general, this project is aimed at providing some insight about the thermal procedures required for ensuring the safety of a satellite mission, easing the tasks for other future missions and contributing to guaranteeing the correct health of both RITA Payload and 3Cat4.

Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura

The world of satellites is evolving very rapidly on the past few years, with satellites going from huge machines with complex and expensive systems, to rapidly getting smaller and smaller. Our satellite, a PocketQube, is a satellite that can fit in one’s hand, being it a cube with sides of 5x5 cm. This type of cubes are the cheapest way of exploring parts of the Earth’s orbit, as well as obtaining information that conventional and much bigger satellites would not even bother to get. This is the case of our satellite, which is aimed to obtain information of Earth’s lower Thermosphere. As it is well known, in these upper parts of the Earth’s atmosphere, the presence of air is almost non-existent and any perturbation to the satellite, or any environmental torque, can cause the satellite to spin without control and not be able to perform its tasks correctly. In the point of view of Attitude Control, this is a serious problem as many satellites require a precise pointing to its objective to perform their job well, and whereas this is almost no problem in bigger satellites as they normally carry complex systems to ensure that attitude, what happens to a satellite that weights less than 100 grams? This thesis aims to find reliable ways to ensure Attitude Control on smaller satellites, and hopefully the conclusions obtained in this thesis can help many other femto-satellites(¡100g) that might have the same problems. As stated, the aim of this project focuses on Attitude Control and Determination Systems, and all the simulations performed will be kept as simple as possible, as our objective is not to deal with complex orbital dynamics, Electro-Magnetic Compatibility (EMC) problems or other complex situations.

Non-terrestrial networks (NTN) are expected to play a key role in extending and complementing terrestrial 5G networks in order to provide services to air, sea, and un-served or under-served areas. This paper focuses the attention on the uplink, where terminals are able to establish a direct link with the NTN at Ka-band. To reduce the collision probability when a large population of terminals is transmitting simultaneously, we propose a grant-free access scheme called resource sharing beamforming access (RSBA). We study RBSA for low Earth orbit (LEO) satellite communications with massive multiple-input multiple-output (MIMO). The idea is to benefit from the spatial diversity to decode multiple overlapped signals. We have devised a blind and open-loop beamforming technique, where neither the receiver must carry out brute-force search in azimuth and elevation, nor are the terminals required to report channel state information. Upon deriving the theoretical throughput, we show that RBSA is appropriate for grant-free access to LEO satellite, it reduces the probability of collision, and thus it increases the number of terminals that can access the media. Practical implementation aspects have been tackled, such as the estimation of the required statistics, and the determination of the number of users. This work has received funding from the ministry of Science, Innovation, and Universities under project TERESATEC2017-90093-C3-1-R (AEI/FEDER,UE) and under grant RTI2018-099841-BI00 and from the Catalan Government (2017-SGR-1479).

The objective of this project is to propose a passive method for orbit determination (OD) of GEO objects using observational data as position measurements. The proposed method use position measurements expressed as right ascension and declination angles, therefore no need of on-board sensors within a satellite are need it to track them using the methodology to be presented in this thesis. The OD method was split in 3 main parts. The perturbed model for the orbit propagator, the initial orbit determination (IOD) methodology to compute initial conditions and a filter algorithm for orbit estimation. We selected an orbit propagator based on state vector and a force model solved by a Runge-Kutta 7-8 numerical integrator. The acting forces considered in the perturbed model were the earth gravitational potential model EGM96 (n=m=70), the third body perturbation due to the moon and sun gravitational forces and the exerted force due to the solar radiation pressure. Since the case study of this project is focused on GEO objects, the perturbation because of atmospheric drag was neglected. Based on the constraints of our observational data, an angles-only method was necessary for the for initial orbit determination implementation. The Gauss method and the Gibbs-Herrick method are the best fit for the position and velocity vector respectively, when short separated observations are used. To achieve precise orbit determination, a estimation algorithm using a Extended Kalman Filter (EKF) method was implemented. The observational data was used as the sensing measurements and the orbit propagator as the state predictor. The results suggested that the EKF can be used to the reduced the uncertainty associated with the orbit propagator error and to avoid this uncertainty to accumulate over the time (up to 3km per day for GEO objects). Nevertheless, future works should discuss and study how to improve the estimation implementations when observations that are closely separated are used as the measurements (separated by less than 1 minute).

Distributed antenna arrays, fractionated payloads and cooperative platforms can provide unprecedented performance in the next generation of spaceborne communications and remote sensing systems. Remote phase synchronization of physically separated oscillators is the first step towards a coherent operation of distributed systems. This work shows the preliminary results of a TDD remote phase synchronization algorithm with a master-follower architecture. Herein, we describe the implementation and validation of the proposed algorithm. The implementation has been conducted in a Cubesat-ready software defined radio and validated at the end-to-end satellite communications testbed available at the University of Luxembourg. This work was supported by the Fond National de la Recherche Luxembourg, under the CORE project COHESAT: Cognitive Cohesive Networks of Distributed Units for Active and Passive Space Applications.

The Microwave Interferometric Reflectometer (MIR) is an airborne GNSS-R instrument developed by Universitat Politècnica de Catalunya. In 2018, it was flown twice over the agricultural Yanco area, New South Wales, Australia, once after a very dry period, and a further time the day after a strong rain event. This rain event resulted in many crop fields being entirely flooded, producing a saturation in the GNSS-R reflectivity value. In this work, the received data set is processed to identify the optimum integration time with the goal to minimize pixel blurring. This issue is assessed for airborne conditions, and then extra-polated to the spaceborne case. The presented results show that the blurring of the GNSS waveform is produced even from an airborne sensor with short integration times. Following the determination of an optimal integration time for the platform in use, the surface roughness term in the reflectivity equation can be isolated due to the signal saturation during very wet surface conditions. The final results from the two channels (L1 C/A and L5) are subsequently presented. In this case, it is shown that most reflectivity variations in GNSS-R measurements are linked to surface roughness and Speckle noise fluctuations rather than soil moisture changes.

The operation of satellites in very low Earth orbit (VLEO) has been linked to a variety of benefits to both the spacecraft platform and mission design. Critically, for Earth observation (EO) missions a reduction in altitude can enable smaller and less powerful payloads to achieve the same performance as larger instruments or sensors at higher altitude, with significant benefits to the spacecraft design. As a result, renewed interest in the exploitation of these orbits has spurred the development of new technologies that have the potential to enable sustainable operations in this lower altitude range. In this paper, system models are developed for (i) novel materials that improve aerodynamic performance enabling reduced drag or increased lift production and resistance to atomic oxygen erosion and (ii) atmosphere-breathing electric propulsion (ABEP) for sustained drag compensation or mitigation in VLEO. Attitude and orbit control methods that can take advantage of the aerodynamic forces and torques in VLEO are also discussed. These system models are integrated into a framework for concept-level satellite design and this approach is used to explore the system-level trade-offs for future EO spacecraft enabled by these new technologies. A case-study presented for an optical very-high resolution spacecraft demonstrates the significant potential of reducing orbital altitude using these technologies and indicates possible savings of up to 75% in system mass and over 50% in development and manufacturing costs in comparison to current state-of-the-art missions. For a synthetic aperture radar (SAR) satellite, the reduction in mass and cost with altitude were shown to be smaller, though it was noted that currently available cost models do not capture recent commercial advancements in this segment..., Comment: 23 pages, 6 figures, Accepted for publication in Acta Astronautica (2021-07-03)

In the recent years, the automotive industry has oriented its research and development efforts towards autonomous and assisted driving. These are critical systems as they must guarantee their robustness and reliability for human life, and therefore they have complex designs and involve the most innovative technologies. Location and positioning system is one of its more challenging mechanisms that requires high availability and precision. For this problem there are many technological approaches, but most common ones are GNSS-like and image recognition solutions. They both have accurate and reliable performance under favourable conditions. However, due to the variability of the environment they also have some points of failure that can result in an accident. In certain adverse conditions, to obtain a precise and reliable localization, further information is needed. Here is where Ultra Wide Band technology (UWB) with support of additional sensing mechanisms such as Inertial Navigation System (INS), can provide additional sources of information. This data fusion is done by means of Kalman Filtering, more concretely the Extended Kalman Filter algorithm, which applies for non-linear systems like the one under study. In this document, the whole positioning system's performance will be analysed and evaluated with some simulations and real scenario tests, comparing the main approaches of the Kalman Filter (linear and non-linear) and obtaining an optimized solution for the positioning mechanism. Also, some conclusions and future work tips will be provided in order to contribute the knowledge in similar areas. En los últimos años, la industria del automóvil ha orientado sus esfuerzos de investigación y desarrollo hacia la conducción autónoma y asistida. Estos son sistemas críticos ya que deben garantizar su robustez y fiabilidad para la vida humana, por lo que adquieren diseños complejos e involucran las tecnologías más innovadoras. El sistema de ubicación y posicionamiento es uno de sus mecanismos más desafiantes que requiere una alta disponibilidad y precisión. Para este problema existen muchos enfoques tecnológicos, pero los más comunes son las soluciones de reconocimiento de imágenes y sistemas GNSS. Ambos tienen un rendimiento preciso y confiable en condiciones favorables. Sin embargo, debido a la variabilidad del entorno también tienen algunos puntos de fallo que pueden resultar en un accidente. En determinadas condiciones adversas, para obtener una localización precisa y fiable, se necesita más información. Aquí es donde la tecnología de banda ultra ancha (UWB) con soporte de mecanismos de detección adicionales como el sistema de navegación inercial (INS), puede proporcionar fuentes adicionales de información. Esta fusión de datos se realiza mediante el filtrado de Kalman, más concretamente el algoritmo de filtro de Kalman extendido, que se aplica a sistemas no lineales como el que se está estudiando. En este documento se analizará y evaluará el desempeño de todo el sistema de posicionamiento con algunas simulaciones y pruebas de escenarios reales, comparando los principales enfoques del Filtro de Kalman (lineal y no lineal) y obteniendo una solución optimizada para el mecanismo de posicionamiento. Asimismo, se brindarán algunas conclusiones y consejos de trabajo futuro con el fin de aportar el conocimiento en áreas similares. En els darrers anys, la indústria de l'automòbil ha orientat els seus esforços de recerca i desenvolupament cap a la conducció autònoma i assistida. Es tracta de sistemes crítics, ja que han de garantir la seva robustesa i fiabilitat per a la vida humana i, per tant, tenen dissenys complexos i impliquen les tecnologies més innovadores. El sistema de localització i posicionament és un dels seus mecanismes més difícils que requereix una alta disponibilitat i precisió. Per a aquest problema hi ha molts enfocaments tecnològics, però els més comuns són solucions similars al GNSS i de reconeixement d'imatges. Tots dos tenen un rendiment precís i fiable en condicions favorables. Tot i això, a causa de la variabilitat de l'entorn, també presenten alguns punts de fracàs que poden provocar un accident. En certes condicions adverses, per obtenir una localització precisa i fiable, es necessita més informació. Aquí és on la tecnologia Ultra Wide Band (UWB) amb suport de mecanismes de detecció addicionals com el sistema de navegació inercial (INS), pot proporcionar fonts d'informació addicionals. Aquesta fusió de dades es fa mitjançant el filtratge de Kalman, més concretament l'algorisme del filtre Kalman estès, que s'aplica a sistemes no lineals com el que s'està estudiant. En aquest document, s'analitzarà i avaluarà el rendiment de tot el sistema de posicionament amb algunes simulacions i proves d'escenaris reals, comparant els enfocaments principals del filtre Kalman (lineal i no lineal) i obtenint una solució optimitzada per al mecanisme de posicionament. A més, es proporcionaran algunes conclusions i futurs consells de treball per tal de contribuir al coneixement en àrees similars.