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The Universitat Politecnica de Catalunya (UPC), the Physikalisch-Technische Bundesanstalt (PTB) and the German Federal Office of Radiation Protection (BfS) have analysed the response of a 2”x2” (diameter x height) NaI and a 1.5”x1.5” CeBr3 scintillators, and a 1500 mm3 CZT semiconductor airborne spectrometric detectors mounted on Unmanned Aerial Vehicles (UAV) in a comparison campaign carried out in the aerial site of Mollerussa (Spain). The background count rates and H*(10) rates measured by the airborne detectors at the aerial site and with a 137Cs point source of 345 MBq have been compared at altitudes of 1.5 m, 10 m, 20 m, 40 m, 60 m and 100 m a.g.l. (above ground level). Furthermore, natural activity concentrations in soil have been calculated with different methodologies using the spectra acquired in the background flights. The airborne detectors together with the implemented calculation methodologies show in general a good agreement. The CZT detector has a significant lower efficiency than both scintillators due to the smaller size and, therefore shows poorer results. Finally, parallel flights over the 137Cs point source at 10 m, 20 m and 40 m were carried to evaluate the methods implemented by the three teams to localize point sources. The three systems were able to locate properly the source. The project 16ENV04 “Metrology for mobile detection of ionising radiation following a nuclear or radiological incident” has received funding from the EMPIR programme co-financed by the participating states and from the European Union’s Horizon 2020 research and innovation programme.

In the circular restricted three-body problem (CR3BP) the weak stability boundary (WSB) is defined as a boundary set in the phase space between stable and unstable motion relative to the second primary. At a given energy level, the boundaries of such region are provided by the stable manifolds of the central objects of the L1 and L2 libration points, i.e., the two planar Lyapunov orbits. Besides, the unstable manifolds of libration point orbits (LPOs) around L1 and L2 have been identified as responsible for the weak or temporary capture around the second primary of the system. These two issues suggest the existence of natural dynamical channels between the Earth's vicinity and the Sun–Earth libration points L1 and L2. Furthermore, it has been shown that the Sun–Earth L2 central unstable manifolds can be linked, through an heteroclinic connection, to the central stable manifolds of the L2 point in the Earth–Moon three-body problem. This concept has been applied to the design of low energy transfers (LETs) from the Earth to the Moon. In this contribution we consider all the above three issues, i.e., weak stability boundaries, temporary capture and low energy transfers, and we discuss the role played by the invariant manifolds of LPOs in each of them. The study is made in the planar approximation.