Jitter Effects on Earth Observation Micro-Satellites

Line-of-Sight (LoS) jitter represents a multidisciplinary challenge to Earth Observation satellites hosting high-performance, vibration-sensitive optical sensor payloads with stringent pointing stability requirements. Micro-vibrations are one of the main factors contributing to platform jitter and can impact the reliability and precision of Earth imagery crucial for various applications. Typically, the all-encompassing jitter solutions for flagship-class observatories, which are generally bespoke, are highly customized mission-unique designs that hire extensive modeling, analysis, and test, which is costly and time consuming. The scenario for non-flagship missions that use “commercial class” small spacecraft is completely different. The ordinary CubeSats’ small dimensions, low-cost solutions and tight timings make jitter managing more arduous and engineering complex. In this Thesis, an integrated methodology is described to achieve a complete LoS jitter analysis on a micro-satellite, considering all the technical areas involved. Three important aspects are tackled: 1) the definition and characterization of the on-board internal disturbance sources, with a focus on reaction wheel assembly (RWA) as the most significant ones; 2) the evaluating of disturbance effects on the spacecraft structure through the delineation of the Frequency Response Function (FRF) from the disturbance source locations to the sensitive payload; 3) the optical performance outcome affected by the disturbances, especially focused on the Modulation Transfer Function (MTF) one of the most important parameters by which image quality is measured. This method is applied to a new high-resolution optical remote-sensing micro-satellite: HAWK for Earth Observation, the platform designed by Argotec in the context of IRIDE mission. The work aims to compare also the predictions obtained by Virtual Engineering Model (VEM), realized using a hybrid FE-SEA model, with the experimental results retrieved during the physical micro-vibration test campaign, which was carried out on the Structural Model (SM) of the satellite in the Argotec facilities in Turin, Italy. Finally, the purpose of the work is to suggest an operative area for the satellite where the disturbance consequences on the image quality are reduced and propose a jitter solution implementable in a “commercial” environment.