Implementation of a GNSS-R payload based on software defined radio for the 3CAT-2 mission

©2016 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.The 3CAT-2 nanosatellite aims at demonstrating global navigation satellite system reflectometry (GNSS-R) techniques for spaceborne applications in the small form of a six-unit CubeSat. There are many challenges involved from a size, processing, and power perspectives. The proposed solution for the payload uses a software-defined radio (SDR) connected to a nadir looking array of dual-band and dual-frequency and dual-polarization antennas to capture the reflected GNSS signals and to a zenith looking patch antenna to capture the direct ones. The SDR is controlled by the payload computer, which retrieves the binary samples and processes the raw data to obtain delay-doppler maps (DDMs) via various techniques. DDMs are then compressed using the fully adaptive prediction error coder algorithm, producing an output more suitable for the limited downlink capabilities of these small platforms.Peer ReviewedPostprint (author's final draft

3 Cat-4 mission, 1-Unit CubeSat for earth observation: Evaluation on the qualification and production during Phase D

The 3Cat-4 mission is a 1-unit CubeSat platform that serves as a technology demonstrator and educational platform for students at Universitat Politècnica de Catalunya (UPC). Promoted by the UPC Nanosatellite and Payload Laboratory (UPC NanoSatLab), the most notable subsystems that innovate in the nanosatellite scenario are (1) the Flexible Microwave Payload - 1 (FMPL-1) [1], a cost-effective payload to execute Global Navigation Satellite System Reflectometry (GNSS-R), and L-band microwave radiometry experiments using a commercial off-the-shelf (COTS) software-defined radio (SDR) and (2) the Nadir Antenna Deployment Subsystem (NADS) [2], an in-orbit deployable high-directivity antenna used by Earth Observation (EO) payloads. This paper presents the findings of the 3Cat-4 mission during Phase D, the qualification and production phase of the project. Since the publication of the first introductory work for this mission in 2019[3], several sections of the subsystems have been redesigned and upgraded to correct previous design flaws or to meet new requirements. In addition, this paper addresses the educational perspective of this mission, analyzing its performance and usefulness in the aforementioned subject

Design and validation of a dual-band circular polarization patch antenna and stripline combiner for the FSSCat mission

The FMPL-2 payload on board the 3Cat-5/A 6 Unit CubeSat, part of the FSSCat CubeSat mission, includes a dual L-Band Microwave Radiometer and a Global Navigation Satellite System Reflectometer, in one instrument, implemented in a Software Defined Radio. One of the design challenges of this payload was its Nadir looking Antenna, which had to be directive (> 12 dB), dual-band at 1400–1427 MHz and 1575.42 MHz, left-hand circularly polarized, and with important envelope restrictions, notably with a low profile. After a trade-off analysis, the best design solution appeared to be an array of six elements each of them being a stacked dual-band patch antenna, with diagonal feed to create the circular polarization, and a six to one stripline combiner. The design process of the elementary antennas first includes a theoretical analysis, to obtain the approximate dimensions. Then, by means of numerical simulations, prototyping, and adjusting the results in the simulations, the manufacturing errors and dielectric constant tolerances, to which patch antennas are very sensitive, can be characterized. A similar approach is taken with the combiner. This article includes the theoretical analysis, simulations, and prototype results, including the Flight Model assembly and characterizationThis work was 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) and in part by the European Social Fund (ESF). It is also funded in part by the Secretaria d’Universitats i Recerca del Departament d’Empresa i Coneixement de la Generalitat de Catalunya 2017 SGR 376 and 2017 SGR 219. This work has also been founded by the grant PID2019-106808RA-I00 funded by MCIN/AEI/10.13039/501100011033. Finally, this research was possible thanks to the FI-2019 grant from AGAUR-Generalitat de Catalunya, Spain.Peer ReviewedPostprint (published version

3Cat-3/MOTS nanosatellite mission for optical multispectral and GNSS-R Earth Observation: concept and analysis

The 3Cat-3/MOTS (3: Cube, Cat: Catalunya, 3: 3rd CubeSat mission/Missió Observació Terra Satèl·lit) mission is a joint initiative between the Institut Cartogràfic i Geològic de Catalunya (ICGC) and the Universitat Politècnica de Catalunya-BarcelonaTech (UPC) to foster innovative Earth Observation (EO) techniques based on data fusion of Global Navigation Satellite Systems Reflectometry (GNSS-R) and optical payloads. It is based on a 6U CubeSat platform, roughly a 10 cm × 20 cm × 30 cm parallelepiped. Since 2012, there has been a fast growing trend to use small satellites, especially nanosatellites, and in particular those following the CubeSat form factor. Small satellites possess intrinsic advantages over larger platforms in terms of cost, flexibility, and scalability, and may also enable constellations, trains, federations, or fractionated satellites or payloads based on a large number of individual satellites at an affordable cost. This work summarizes the mission analysis of 3Cat-3/MOTS, including its payload results, power budget (PB), thermal budget (TB), and data budget (DB). This mission analysis is addressed to transform EO data into territorial climate variables (soil moisture and land cover change) at the best possible achievable spatio-temporal resolution.Peer ReviewedPostprint (published version

Contributions to GNSS-R earth remote sensing from nano-satellites

Premi extraordinari doctorat UPC curs 2015-2016, àmbit de CiènciesGlobal Navigation Satellite Systems Reflectometry (GNSS-R) is a multi-static radar using navigation signals as signals of opportunity. It provides wide-swath and improved spatio-temporal sampling over current space-borne missions. The lack of experimental datasets from space covering signals from multiple constellations (GPS, GLONASS, Galileo, Beidou) at dual-band (L1 and L2) and dual-polarization (Right Hand Left Hand Circular Polarization: RHCP and LHCP), over the ocean, land and cryosphere remains a bottleneck to further develop these techniques. 3Cat-2 is a 6 units (3 x 2 elementary blocks of 10 x 10 x 10 cm3) CubeSat mission ayming to explore fundamentals issues towards an improvement in the understanding of the bistatic scattering properties of different targets. Since geolocalization of specific reflections points is determined by the geometry only, a moderate pointing accuracy is still required to correct for the antena pattern in scatterometry measurements. 3Cat-2 launch is foreseen for the first quarter 2016 into a Sun-Synchronous orbit of 510 km height using a Long March II D rocket. This Ph.D. Thesis represents the main contributions to the development of the 3Cat-2 GNSS-R Earth observation mission (6U CubeSat) including a novel type of GNSS-R technique: the reconstructed one. The desing, development of the platform, and a number of ground-based, airborne and stratospheric balloon experiments to validate the technique and to optimize the instrument. In particular, the main contributions of this Ph.D. thesis are: 1) A novel dual-band Global Navigation Satellite Systems Reflectometer that uses the P(Y) and C/A signals scattered over the sea surface to perform highly precise altimetric measurements (PYCARO). 2) The first proof-of-concept of PYCARO was performed during two different ground-based field experiments over a dam and over the sea under different surface roughness conditions. 3) The scattering of GNSS signals over a water surface has been studied when the receiver is at low height, as for GNSS-R coastal altimetry applications. The precise determination of the local sea level and wave state from the coast can provide useful altimetry and wave information as "dry" tide and wave gauges. In order to test this concept an experiment has been conducted at the Canal d'Investigació i Experimentació Marítima (CIEM) wave channel for two synthetic "sea" states. 4) Two ESA-sponsored airborne experiments were perfomed to test the precision and the relative accuracy of the conventional GNSS-R. 5) The empirical results of a GNSS-R experiment on-board the ESA-sponsored BAXUS 17 stratospheric balloon campaign performed North of Sweden over boreal forests showed that the power of the reflected signals is nearly independent of the platform height for a high coherent integration time. 6) An improved version of the PYCARO payload was tested in Octover 2014 for the second time during the ESA-sposored BEXUS-19,. This work achieved the first ever dual-frequency, multi-constellation GNSS-R observations over boreal forests and lakes using GPS, GLONASS and Galileo signals. 7) The first-ever dual-frequency multi-constellation GNSS-R dual-polarization measurements over boreal forests and lakes were obtained from the stratosphere during the BEXUS 19 using the PYCARO reflectometer operated in closed-loop mode.Global Navigation Satellite Systems Reflectometry (GNSS-R) es una técnica de radar multi-estático que usa señales de radio-navegación como señales de oportunidad. Esta técnica proporciona "wide-swath" y un mejor sampleado espacio-temporal en comparación con las misiones espaciales actuales. La falta de datos desde el espacio proporcionando señales de múltiples constelaciones (GPS, GLONASS, Galileo, Beidou) en doble banda (L1 y L2) y en doble polarización (RHCP y LHCP) sobre océano, tierra y criosfera continua siendo un problema por solucionar. 3Cat-2 es un cubesat de 6 unidades con el objetivo de explorar elementos fundamentales para mejorar el conocimiento sobre el scattering bi-estático sobre diferentes medios dispersores. Dado que la geolocalización de puntos de reflexión específicos está determinada solo por geometría, es necesario un requisito moderado de apuntamiento para corregir el diagrama de antena en aplicaciones de dispersometría. El lanzamiento del 3Cat-2 será en Q2 2016 en una órbitra heliosíncrona usando un cohete Long March II D. Esta tesis representa las contribuciones principales al desarrollo del satélite 3Cat2 para realizar observación de la tierra con GNSS-R incluyendo una nueva técnica: "the reconstructed-code GNSS-R". El diseño, desarrollo de la plataforma y un número de experimentos en tierra, desde avión y desde globo estratosférico para validar la técnica y optimizar el instrumento han sido realizados. En particular, las contribuciones de esta Ph.D. son: 1) un novedoso Global Navigation Satellite Systems Reflectometer que usa las señales P(Y) y C/A después de ser dispersadas sobre la superficie del mar para realizar medidas altimétricas muy precisas. (PYCARO). 2) La primera prueba de concepto de PYCARO se hizo en dos experimentos sobre un pantano y sobre el mar bajo diferentes condiciones de rugosidad. 3) La disperión de las señales GNSS sobre una superfice de agua ha sido estudiada para bajas altitudes para aplicaciones GNSS-R altimétricas de costa. La determinación precisa del nivel local del mar y el estado de las olas desde la costa puede proporcionar información útil de altimetría e información de olas. Para hacer un test de este concepto un experimento en el Canal d'Investigació i Experimentació Marítima (CIEM) fue realizado para dos estados sintéticos de rugosidad. 4) Dos experimentos en avión con esponsor de la ESA se realizaron para estudiar la preción y la exactitud relativa de cGNSS-R. 5) Los resultados empíricos del experimento GNSS-R en BEXUS 17 con esponsor de la ESA realizado en el norte de Suecia sobre bosques boreales mostró que la potencia reflejada de las señales es independiente de la altitud de la plataforma para un tiempo de integración coherente muy alto. 6) Una versión mejorada del PYCARO fue testeada en octubre del 2014 por segunda vez durante el BEXUS 19 que también fue patrocidado por la ESA. Este trabajo proporcionó las primeras medidas GNSS-R sobre bosques boreales en doble frecuencia usando varias constelaciones GNSS. 7) Las primeras medidas polarimétricas (RHCP y LHCP) de GNSS-R sobre bosques boreales también fueron conseguidas durante el experimento BEXUS 19.Award-winningPostprint (published version

Design, implementation and verification of CubeSat systems for Earth Observation

In recent years, Earth Observation (EO) technologies have surged in an attempt to better understand the world we live in, and exploit the vast amount of data that can be collected to improve our lives. The field of EO encompasses a broad array of technologies capable of extracting information remotely, in a process called Remote Sensing (RS). CubeSats are causing a revolution in the RS field, and are becoming a really important contribution to it. The lack of testing and preparation are common in CubeSat EO missions due to the low budgets they usually suffer from. A successful CubeSat EO mission must supply the lack of size or funding with properly tested components and environments. In this document, emphasis will be given to preemptive approaches such as studying the performance of Commercial Off-The-Shelf (COTS) Global Positioning System (GPS) receivers and the development of simulators for highly dynamic environments This topic will be expanded upon by introducing the problematic of simulating such signals for testing, and the possible countermeasures to Radio-Frequency Interference (RFI) that threatens the success of the mission. Finally, a new S-Band Ground Station will be built to provide access to this band for future CubeSat missions. All of the above will provide a holistic view on some of the hot challenges that EO faces, and multiple future research paths that open with the recent rise of New Space technologies

GNSS transpolar earth reflectometry exploriNg system (G-TERN): mission concept

The global navigation satellite system (GNSS) Transpolar Earth Reflectometry exploriNg system (G-TERN) was proposed in response to ESA's Earth Explorer 9 revised call by a team of 33 multi-disciplinary scientists. The primary objective of the mission is to quantify at high spatio-temporal resolution crucial characteristics, processes and interactions between sea ice, and other Earth system components in order to advance the understanding and prediction of climate change and its impacts on the environment and society. The objective is articulated through three key questions. 1) In a rapidly changing Arctic regime and under the resilient Antarctic sea ice trend, how will highly dynamic forcings and couplings between the various components of the ocean, atmosphere, and cryosphere modify or influence the processes governing the characteristics of the sea ice cover (ice production, growth, deformation, and melt)? 2) What are the impacts of extreme events and feedback mechanisms on sea ice evolution? 3) What are the effects of the cryosphere behaviors, either rapidly changing or resiliently stable, on the global oceanic and atmospheric circulation and mid-latitude extreme events? To contribute answering these questions, G-TERN will measure key parameters of the sea ice, the oceans, and the atmosphere with frequent and dense coverage over polar areas, becoming a “dynamic mapper”of the ice conditions, the ice production, and the loss in multiple time and space scales, and surrounding environment. Over polar areas, the G-TERN will measure sea ice surface elevation (<;10 cm precision), roughness, and polarimetry aspects at 30-km resolution and 3-days full coverage. G-TERN will implement the interferometric GNSS reflectometry concept, from a single satellite in near-polar orbit with capability for 12 simultaneous observations. Unlike currently orbiting GNSS reflectometry missions, the G-TERN uses the full GNSS available bandwidth to improve its ranging measurements. The lifetime would be 2025-2030 or optimally 2025-2035, covering key stages of the transition toward a nearly ice-free Arctic Ocean in summer. This paper describes the mission objectives, it reviews its measurement techniques, summarizes the suggested implementation, and finally, it estimates the expected performance.Peer ReviewedPostprint (published version

Implementation of a flowgraph-based satellite operations software for Earth Observation missions

This project aims to develop mission-critical software that facilitates the monitoring and automation of the operations plan between the Operation Center and the CubeSats. This software will assist operators in various tasks, including scheduling satellite passes, controlling one or multiple Ground Stations to follow the satellite, preparing execution plans with contingencies for all the different steps in the communication protocol, and automating these processes. To minimize errors introduced by operators, the software will offer an interactive user interface for configuring message sets and information exchange during contact. It will also allow for the setup of conditional blocks that depend on received data, creating a seamless and error-free feedback loop. The objective is to gradually reduce the operator's workload, to the point of making their interaction unnecessary. This will enable automated communication with the satellite at any time of day. As part of the operations, all uploaded and downloaded data will be stored for posterior processing, with automated processing wherever possible. The software will be developed using the Rust programming language, known for its speed, memory safety, and thread safety. Rust compiler detects a significant amount of common errors at compile-time, this will allow the development of a highly reliable and high-performance application. While the project will initially focus on supporting the 3Cat-4 satellite, it will also create the basis to operate any other satellite in the future, such as the RITA Payload

Development of a drone-based miniaturized Flexible Microwave Payload (FMPL) for GNSS-Reflectometry and L-band radiometry

This project has been developed in collaboration with the NanosatLab UPC, which develops CubeSats for educational and scientific purposes and in-orbit technology demonstration. More specifically, the laboratory is focused on remote sensing systems. In recent years, the NanosatLab UPC has been developing the Flexible Microwave PayLoad (FMPL), the integration of different microwave remote sensing equipment in a single system: reflectometry Global Navigation Satellite System (GNSS) signals (GNSS-R) and microwave radiometry (MWR) in L-band. In 2022, the second version of this system, FMPL-2, is in orbit on board the CubeSat 3Cat5, which has provided precious scientific data on the climate of the earth and the evolution of climate change. The first version, FMPL-1, will be launched in the coming months aboard CubeSat 3Cat4. The third version, FMPL-3, is now ready for launch on board the CubeSat GNSSaS. From space, FMPL has proven to be a very useful tool for studying climate change. This work aims to design, build and test the first FMPL for drones, the FMPL-D. This new platform will be used to evaluate new versions of FMPL. It will also be a valuable tool to study the characteristics of soil, water, ice and vegetation locally and with a spatial resolution much greater than that which can be obtained from a satellite. The results presented in this thesis put the complexity of these systems into perspective. Firstly, in the results of the radiometer, an effect of distortion and destruction of the data obtained due to the radio frequency interference received during the measurement campaigns has been observed, highlighting the need for detection and mitigation systems interference for ground observation missions. For the GNSS reflectometry instrument, multiple flights were conducted in which large amounts of data were collected, the processing of which is still in progress. Preliminary results indicate good characteristics of the radio frequency chain. This Final Degree Project (TFG) is the first version of the FMPL-D, culminating in the system's first version and many lessons learned.Objectius de Desenvolupament Sostenible::13 - Acció per al Clim

High Speed S-band Communications System for Nanosatellites

3Cat-3 is a nanosatellite based on the 6 unit cubesat standard. Its payload is an optical multispectral imager that imposes stringent downlink requirements for a nanosatellite. This TFG is based on the experience gained in 3Cat-1 and 3Cat-2 communications systems to develop a "high speed" (goal >= 5 Mbps) downlink for nanosatellites based on the TI CC3200.In order to accomplish the objectives of the next generation of nanosatellites high-speed downlinks have to be designed. This goal faces stringent design constraints as nanosatellites are limit in power, processing capabilities and dimensions. In the quest for higher bit rates the widely used VHF band has to be replaced for higher frequency bands and the link budged margin tightened, decreasing the SNR at reception. The proposed solution uses COTS 2.4 GHz WiFi adapters as transceivers. Range limitations imposed by the default 802.11 mode of operation are bypassed by using packet forging and injection at transmission jointly with monitor mode at reception. A loss-resilient unidirectional downlink is achieved by using application-layer encoding by means of LPDC-Staircase codes. This solution has been already implemented in 3CAT-2, a 6 unit cubesat GNSS-R mission to be launched in July 2016. In addition, bursts of errors are combated by using Reed-Solomon. The system has been tested under Doppler shift and scintillation effects, and a 188Km link between Barcelona and Mallorca has been performed, showing satisfactory results