Saturn's largest natural satellite, Titan, is an icy moon expected to harbour a liquid sub-surface water ocean capable of habiting extra-terrestrial life. The spherical harmonic expansion of the gravity field and the tidal Love number k2 can be used to estimate densities, depths, and phases of different layers from Titan’s interior structure, granting insight on the sub-surface ocean and its habitability. Recent research has determined the spherical harmonic expansion of the gravity field up to degree five including the estimation of Titan’s tidal Love number k2. This work estimates the spherical harmonic gravity field of Titan up to degree three through a multi-arc batch weighted least squares approach, with fundamental differences from previous research. We include observation biases and empirical accelerations for estimation in our dynamic force model and apply no constraints on the gravity and tidal parameters for estimation. Previous research claims the applied global constraints do not constrain the solution, yet an independent estimation of the gravity and tides of Titan yields significantly different results: high correlation between global parameters results in the inability to determine a realistic k2 Love number. We refrain from applying any global constraints to the gravity and tidal parameters, as there exists no a priori information on these parameters to apply a physical and unbiased constraint.

In the Netherlands, the ministry of Security and Justice (VenJ) has the task to ensure the safety of civilians of the Netherlands by enforcing the legal order. The ministry of VenJ wants to solve issues faster and more efficiently by using satellite technology to contribute to a safer and more just Netherlands. The ministry of VenJ asked the Delft University of Technology to perform a feasibility study and design a National Safety System (NSS). Therefore, the mission need statement of this project is to ensure the safety and security of the Netherlands by preforming the use of: an identification and tracking system (ITS) to track specific objects marked by the Ministryl. A fire and smoke detection system that uses earth observation techniques and is able to perform chemical analysis of gas and smoke clouds. Chemical analysis of the smoke clouds is performed in order to identify the presence of toxic substances. This allows populated areas to be evacuated in case the toxic clouds reach these areas. For target tracking the ministry currently uses beacons that emit radio waves to track or follow targets. This requires a lot of manpower and is easily detected, therefore a more efficient way of ensuring the safety of the citizens of the Netherlands has to be designed...