Greenhouse gas monitoring satellites are crucial for understanding climate change and assessing the effectiveness of climate policies. This project explores a novel concept for a metasurfaced-based spectrometer in the short-wave infrared domain. Metasurfaces are artificial planar materials with subwavelength structures that can manipulate light. This project's metasurface is designed with phase change materials to function as a reconfigurable spectral filter. Filter-based spectroscopy is realized by exploiting a compressive sensing algorithm. Using the rigorous coupled wave analysis solver of Ansys Lumerical, different metasurface designs are simulated and evaluated on their transmission response and compressive sensing performance. The final metasurfaces are obtained using particle swarm optimization with a performance metric that balances computation time and accuracy. The results show great promise for accurate and precise reconstruction of the atmospheric absorption spectrum, required for greenhouse gas monitoring.

Saturn's icy moon, Enceladus, has captivated scientists since NASA's Cassini spacecraft discovered massive plumes of water vapour and ice erupting from its south pole. The goal of this study was to present a novel opportunity to characterise the particles in the plumes by searching for optical phenomena such as rainbows and halos in the geysers of Enceladus using Cassini's remote sensing data. During several flybys, we discovered unusual stripe-like patterns within these plumes using simultaneous observations in the Cassini VIMS (Visible and Infrared Mapping Spectrometer) and ISS (Imaging Science Subsystem). This anomaly, unlike any other known optical phenomenon, indicates the presence of an inclined, periodic, millimetre-sized structure in the Saturnian system. We propose two hypotheses for these patterns: they may be caused by a periodic structure in Saturn's Norse group orbits or the E-ring. This unexpected discovery could offer new insights into the particle dynamics within Saturn's environment.

Since their first use during the Apollo 15, 16, and 17 missions, laser altimeters have become indispensable for planetary exploration, enabling topographic mapping of rocky bodies throughout the solar system. The latest European contributions in this field are represented by the BepiColombo Laser Altimeter (BELA) and the Ganymede Laser Altimeter (GALA), developed by the DLR Institute of Planetary Research and currently en route to Mercury and the Jovian moons, respectively. However, to date, such instruments have only been deployed on large satellites, failing to meet miniaturised systems' SWaP (Size, Weight, and Power) requirements.

This thesis investigates the adaptation of laser altimeter technology for smaller platforms, focusing on the NLA (New Laser Altimeter) developed for the SER3NE (Selene's Explorer for Roughness, Regolith, Resources, Neutrons, and Elements) mission proposal. The instrument aims to improve the precision of Lunar topographic data to support the characterisation of future landing sites for crewed missions from a 12 U microsatellite. To meet the stringent SWaP constraints, the design will feature a transceiver and a single-photon detection system — an approach never previously applied to topographic altimeters.

This thesis aims to develop an optical design that fits the instrument within a 3 U volume. Given the innovative nature of the design, a trade-off analysis was conducted to evaluate several configurations based on their compactness, cross-coupling between the laser source and detector, footprint size at the target, co-alignment between the transmitter and receiver, and transmission losses. The selected design stood out in providing a footprint size in the range allowed by the requirements, reducing the probability of damage to the detector due to internal reflections from the laser, and guaranteeing a more stable co-alignment between the transmitter and receiver paths. It includes a transmitter with two 45° folding mirrors, a borehole mirror that allows the laser to pass while deflecting the returning signal, and a shared telescope.

A test campaign is then conducted on a dedicated optomechanical design to assess 1) its compliance with some trade-off criteria and 2) its functionality. The expansion performance is demonstrated as predictable and reliable, guaranteeing the desired divergence and footprint at the target. On the other hand, the transmittance is increased above the constraints by varying the angle of incidence of the light on the band-pass filter. For the functional tests, the quality of the wavefront is first evaluated, resulting in an aberration-free transmitter and a slightly worse receiver, but still acceptable for altimetry applications. Finally, the prototype is aligned thoroughly and tested for timing measurements with single-pixel detectors, successfully providing the range to the target.

In the next instrument development phase, throughout the pre-phase A studies in collaboration with ESA (European Space Agency) and relevant companies, the prototype will be enhanced to verify the performance in the other criteria and test its functionality in a relevant environment with a flight campaign.

Ariel is an ESA space telescope planned for launch in 2029. It is aimed at observing ∼1,000 exoplanets using transit spectroscopy at infrared wavelengths between 0.5-7.8μm, to characterise the chemical composition and thermal structure of their atmospheres. To detect minute flux variations and confidently extract the exoplanet signal, Ariel requires good instrumental flux stability. Moreover, the instrumental response must be monitored through time, and instrumental effects and stellar noise must be estimated and minimised to get as close as possible to the photon noise limit. To do this, Ariel must be calibrated in-flight by observing a set of stellar calibrators, stars whose spectral energy distribution is assumed to be well-studied and constant. This project is aimed at building the stellar calibrator catalogue for Ariel and looking for possible correlations between stellar properties and flux stability. This can also serve as a base study for future space missions other than Ariel. A starting candidate sample mainly including G dwarfs that were observed by TESS is filtered with a three-step procedure using the Lomb-Scargle periodogram and the reduced chi-squared statistic. Assuming an Ariel 3σ flux stability requirement of 100ppm over 6 hours, the defined Ariel Catalogue comprises 581 stars. These are fairly homogeneously distributed over the sky, without periodic variability, and without a large flux excess dispersion. It is found that when selecting the correct effective temperature ranges (5, 000 < Teff < 6, 300K), the probability of finding stable stars is almost constant at 30%. Only the dimmer stars seem to have a higher probability of passing the selection, which is possibly due to the higher noise in the data which makes variability more difficult to identify. Note, however, that the catalogue defined in this study still comprises calibrator candidates. The noise in TESS light curves is probably too high to effectively analyse the stability within the current requirement. So, follow-up observations of these stars with a lower noise are recommended, for instance with PLATO, to greenlight them as final Ariel calibrators.

Synthetic Aperture Radars (SAR) have demonstrated to be great instruments for space-based Earth observation in the microwave frequency. Metasurface antennas, on the other side, are a new type of planar antennas with a great potential for space applications, as they are compact and easy to produce. Several methods have been developed in the past years addressing one or many parts of the design and applications of these antennas, which rely in more or less measure in locally developed tools. However, some parts of these methods can take a great amount of time to implement, making this process more difficult than it should especially if the user has commercial electromagnetic simulation tools available that could accelerate this process. In this work, different procedures have been adapted to the design of a high-gain SAR anisotropic metasurface antenna for a multi-static Earth observation mission, showing that the proposed methodology produces accurate results.