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With the entry barrier for conventional small satellites continuously increasing for uni- versities and researches, this thesis means to promote a more accessible option in the form of a single unit picosatellite (1P). In this report, the design, implementation and testing procedures, alongside with the general mode of operation of these otherwise called PocketQubes will be presented. Three different configurations will be defined by means of three payloads: a VGA camera and two RFI Monitoring Receivers, at L-band and K-band. The avionics, constituting of an EPS, OBC, COMMS and an ADCS will remain mostly unchanged between the three variants. An IEEE GRSS initiative, the project has taken place, from designing to implementation and testing, within UPC?s NanoSat Lab, and is scheduled to be delivered in the shape of a kit, containing the Flight Models fully equipped with a set of manuals and tutorials for assembly, testing and operation, at the end of 2022. Additionally, a flight opportunity is envisioned for two of these PocketQubes aboard the NanoSat Lab?s future 3Cat-8 mission. Con la barrera de entrada de los pequeños satélites convencionales en continuo aumento para las universidades e investigadores, esta tesis pretende promover una opción más accesible en forma de un picosatélite de una sola unidad (1P). En este informe, el diseño, la implementación y los procedimientos de prueba, junto con el modo general de funcionamiento de estos, también llamados PocketQubes, serán presentados. Se definirán tres configuraciones diferentes mediante tres cargas útiles: una cámara VGA y dos receptores de monitorización RFI, uno en banda L y otro en banda K. La aviónica, constituida por los subsistemas EPS, OBC, COMMS y ADCS, permanecer a prácticamente sin cambios entre las tres variantes. El proyecto, una iniciativa del GRSS del IEEE, se ha llevado a cabo desde el diseño hasta la implementación y las pruebas en el NanoSat Lab de la UPC, y está previsto que se entregue en forma de kit, conformado por los modelos de vuelo Amb la barrera d’entrada als petits satèl·lits convencionals en augment continu per a les universitats i investigadors, aquesta tesi tracta de facilitar l’accés a una opció més assequible, en forma d’un picosatèl·lit d’1P. En aquest treball es presenten els procediments de disseny, implementació i proves realitzades, conjuntament amb els modes generals de funcionament d’aquests satèl·lits, anomenats PocketQubes. Es definiran tres configuracions diferents, segons la carrega útil a bord: una càmera VGA i dos sensors de RFI, un en banda L i l’altre en banda K. L’aviònica, constituïda per una EPS, una OBC, un sistema COMMS i el mòdul ADCS, romandrà pràcticament sense alteracions entre els tres models. Aquest projecte és una iniciativa del GRSS de l’IEE, i s’ha executat, des del disseny fins a la implementació i verificació, a les instal·lacions del NanoSat Lab de la UPC, i està pendent de ser entregat com a kit complet, incloent-hi els models de vol i el conjunt de manuals i tutorials de muntatge, proves i la operació, a finals de 2022. A més, es preveu una oportunitat de vol per a dos d’aquests PocketQubes a bord de la futura missió 3Cat-8 del NanoSat Lab.

Due to an increasing entry barrier to both universities and researchers in conventional small satellites initiatives, there has been an emergence of smaller and cheaper spacecrafts like PocketQubes, a much more affordable option for public entities. Considering all that, this thesis has been developed as part of a project undertaken by the UPC NanoSat Lab which started as an IEEE GRSS initiative named PoCat. The objective of the PoCat project is to design, develop and test three single unit picosatellites with each featuring the following different payloads, a Video Graphics Array (VGA) camera, a Radio Frequency Interference (RFI) monitoring system at L-band and an RFI monitoring system at K-Band. The three satellites, however, contain the same avionics core composed of the On-Board Computer (OBC), Communication System (COMMS), Attitude Determination and Control System (ADCS) and Electrical Power Supply System (EPS). Given this scenario, the purpose of this report is to give insights regarding the on-board software development for PocketQubes, which as of writing this report there is still room for debate concerning their standardization. Conceptually, the OBC system acts as the brain of the satellite. As for the technology, the OBC is build upon the STM32L476 microcontroller due to its memory storage, power efficiency and processing power. Performing the power management as well as giving response to events are the main objectives of the OBC. In order to do the latter, the flight software is based on a Real-Time Operating System (RTOS) called FreeRTOS which has been selected above other Operating System (OS) due to its predictability, compliance with the required deadlines, support, available documentation, compatibility with previous projects, licensing costs, and certifications. According to FreeRTOS, the program is structured into independent tasks where each one features a priority in line with their criticality. Then, the project is constituted by eight tasks, with five designed to operate the subsystems of the satellite, one for memory writing purposes and the remaining two are devoted to implement FreeRTOS software timers. Furthermore, tasks can communicate with each other by means of task notifications or event groups, both being software tools provided by the operating system.