Introduction

The 21st century stands out in the history of human societies as a time of transition. We are witnessing a period in the history of humankind that allows for all kinds of lifestyle breakthroughs, thanks to the increase in entropy associated with the various degrees of freedom of action and activity possible. One of these fields of activity concerns the space age and the NewSpace era. The name could have been different, because the term "New" refers to something new, whereas the "Universe" has always been there. Technological prowess has enabled us to reach that which aroused the curiosity of the first astronomers.

The industrial revolution 4.0 of the 21st century prefigured the expected increase in the processes used in business activities. These are based on digital technologies using algorithms predefined by objectives, such as system integration, augmented reality, virtual reality, the digital twin, artificial intelligence (AI), short- and long-term logistics, data analysis for processing large databases, cybersecurity, the autonomous robot, additive manufacturing, the Internet of Things, cloud computing, bitcoin and the simulation of complex chemical and biological processes in biotechnologies (infotech, biotech, etc.).

Software development is driving digital transition processes and impacting decision-making support with the breakthroughs and democratization of AI. It should be noted that the contribution of IT tools and the development of technologies in the field of genetics and human genome sequencing since the 2000s have led to the emergence of a new discipline called paleogenomics. This was initiated by the recent Nobel Prize winner in Medicine and Physiology, Svante Pääbo, in 2022, as part of the study of ancient DNA through paleogenetics.

Alongside this reality, which is moving towards the 4.0+ revolution, we are observing through NewSpace a desire to increase our degrees of freedom. This is leading us towards a new path, which may allow for the privatization of space and the realization of the dream of conquering space and the Universe.

The first two satellites, Sputnik 1 and Sputnik 2, were launched by the USSR in 1957, on October 4 and November 3, while Explorer 1 and Vanguard 1 were launched by the Americans shortly afterwards, in 1958, on February 1 and March 17. The first major discovery was the Van Allen belts by the Americans who, thanks to a magnetic recorder on board Explorer 3, were able to correctly interpret the signals transmitted by the first satellites, which had remained an enigma until then. These belts are named after Van Allen, who, with his team, developed many of the observation instruments carried as payloads on American satellites.

Technological advances and strategies for space exploration and observation have thus followed a trajectory. In its initial phase, in the 1960s, this trajectory began with a typology of satellites, either spherical or cylindrical in shape, with masses of no more than a hundred kilos, equipped with the latest technologies. From the mid-1970s to the present day, it has evolved towards more elaborate technological objects, exceeding a few thousand kilos and up to tens of tons.

The history of space exploration can be divided into several distinct periods. The foundations for this adventure were laid as early as 1957, with the acquisition of the knowledge and technologies needed to send man into space. The period from 1957 to the end of the Apollo program in 1972 was characterized by major advances, and is often referred to as the golden age of space exploration. During this period, the two world superpowers of the time, the United States and the Soviet Union, indirectly engaged in space competition.

The next period, from 1972 until the end of the Cold War in the early 1990s, was marked by geopolitical issues in an increasingly militarized environment. Satellites were mainly developed for military purposes, such as observation, listening, communication and navigation. At the same time, space research was booming, leading to major advances in scientific research and increased international cooperation.

Since the end of the Cold War in 1991, space exploration has evolved in a context of unipolar domination, with the United States in a predominant position. In the late 1990s, the NewSpace era emerged, marked by growing private initiative in the space industry. Enterprising personalities such as Elon Musk (SpaceX), Jeff Bezos (Blue Origin) and Richard Branson (Virgin Galactic) played a key role in this new era, with ambitious goals such as the exploration of Mars, the Moon and suborbital flights. NewSpace brings a new dynamic to the space industry, thanks to reusable launchers and the miniaturization of satellites.

Meanwhile, in 1999, California Polytechnic State University and Stanford University (USA) invented a new satellite format. It opened up new prospects for Earth observation. In 1999, as part of an educational project to imagine, design, implement, test and operate in space a complete spacecraft within a reasonable timeframe, as part of a three- to five-year program to train university students, CubeSats - cubes measuring 10 × 10 × 11.35 cm (1U) - were created in California. They ushered in a new era in the conquest of space.

The immensity of the cosmos seemed essentially cold and barren until the middle of the 20th century, but the launch of Sputnik 1 marked the beginning of the space age. The dispatch of robotic scientific explorers across the Solar System, space observatories in Earth orbit, the development of advanced detection techniques and increasingly powerful telescopes have enabled us to acquire new knowledge through observation from space. All of this has completely revolutionized our vision of both planetary atmospheres and the interstellar medium, revealing an unsuspected molecular richness leading to the creation, alongside astrophysics, of new disciplines such as astrochemistry. In the wake of these developments, models of molecular physics and chemistry have made it possible to study chemical species using the theory of quantum mechanics, providing reliable, precise and high-quality analysis through spectroscopy. This tool provides the necessary information on parameters such as pressure, temperature, humidity, wind speed or solar flux, to understand the processes driving the dynamics of planetary atmospheres, particularly that of the Earth.

Thanks to ground-based microwave observatories in very dry, high-altitude regions (ALMA) or airborne observatories (stratospheric balloons, SOFIA), astrophysicists have access to a large battery of instruments dedicated to spectroscopy. These include spectrometers onboard space probes bound for Venus (Venus Express), Mars (Mars Express, TGO, etc.), Jupiter (Junon), Saturn (Cassini-Huygens), comets (Rosetta) or the terrestrial-based JWST (James Webb Space Telescope) observatory.

The future looks exciting in this field, with future observatories on Earth (E-ELT, etc.), in space (WFIRST) and on various planetary missions. The constellation of nanosatellites will enable us to refine the precision of our spatial and temporal measurements.

This book is the first of three and discusses the space age from its origins in the mid-20th century, through to the NewSpace era of the 21st century. Its content is drawn from lectures and seminars by Meftah, Dahoo and El Hami as part of their teaching and research activities. It also draws on feedback from research activities at the Laboratoire Atmosphères et Observations Spatiales (LATMOS) and at INSA Rouen, resulting from research work in the fields of instrumentation and spectroscopy for astronomy and astrophysics as well as optimization in mechanics. Our research teams are also involved in space observation, both through the implementation of observation instruments and through the analysis of observation data in partnership with other national institutes and organizations (CNES, ONERA, etc.), international organizations (ESA, Institut royal d'aéronomie spatiale de Belgique (IASB), Institut Lafayette, Jet Propulsion Laboratory, etc.) or industrial partners (AMSAT-F, F6KRK, Electrolab, ACRI-ST, Adrelys, Hensoldt Space Consulting, Oledcomm, Nanovation, etc.), to name a few.

The aim of this book is to provide an overview of the knowledge required to build and use nanosatellites to observe the atmosphere of a planet, in particular the Earth, and to provide the spectroscopic tools needed to study them and the data required to understand global warming. It is presented from a systems engineering or systemic approach. Each chapter includes an appendix presenting the necessary mathematical, physical and mechanical knowledge, so that readers who wish to delve deeper into the concepts developed in the body of the chapter can do so. The bibliography, although not exhaustive, is substantial enough to allow for further reading.

Feedback from both CubeSat production and observation using the instruments on board UVSQ-SAT and INSPIRE-SAT 7 (International Satellite Program in Research and Education), launched in 2021 and 2023 respectively, are used to provide researchers, engineers, teachers and students in engineering schools, masters and bachelors programs, as well as business leaders, with the knowledge they need to engage in the socio-economic activities of NewSpace.

This first volume contains four chapters tracing the evolution of the space age and the context of a space observation mission using CubeSats as examples. CubeSats are within the reach of any group who wish to undertake them, thanks to their low cost and short implementation times. They can be used to collect data for the study...