On the Stability of Artificial Equilibrium Points in the Circular Restricted Three Body Problem

The article analyses the stability properties of minimum-control artificial equilibrium points in the planar circular restricted three-body problem. It is seen that when the masses of the two primaries are of different orders of magnitude, minimum-control equilibrium is obtained when the spacecraft is almost coorbiting with the second primary as long as their mutual distance is not too small. In addition, stability is found when the distance from the second primary exceeds a minimum value which is a simple function of the mass ratio of the two primaries and their separation. Lyapunov stability under non-resonant conditions is demonstrated using Arnold’s theorem. Among the most promising applications of the concept we find solar-sail-stabilized observatories coorbiting with the Earth, Mars, and Venu

Earth Delivery of a Small NEO with an Ion Beam Shepherd

The possibility of capturing a small Near Earth Asteroid (NEA) and deliver it to the vicinity of the Earth has been recently explored by different authors. The key advantage would be to allow a cheap and quick access to the NEA for science, resource utilization and other purposes. Among the different challenges related to this operation stands the difficulty of robotically capturing the object, whose composition and dynamical state could be problematic. In order to simplify the capture operation we propose the use of a collimated ion beam ejected from a hovering spacecraft in order to maneuver the object without direct physical contact. The feasibility of a possible asteroid retrieval mission is evaluated

Adaptive scheme for Accurate orbit propagation

Two extensions of the fast and accurate special perturbation method recently developed by Peláez et al. are presented for respectively elliptic and hyperbolic motion. A comparison with Peláez?s method and with the very efficient Stiefel- Scheifele?s method, for the problems of oblate Earth plus Moon and continuous radial thrust, shows that the new formulations can appreciably improve the accuracy of Peláez?s method and have a better performance of Stiefel-Scheifele?s method. Future work will be to include the two new formulations and the original one due to Peláez into an adaptive scheme for highly accurate orbit propagatio

Avian tuberculosis in a Lady Amherst’s pheasant Chrysolophus amherstiae

We report a case of a Lady Amherst’s pheasant (Chrysolophus amherstiae) with diffuse granulomatous lesions in liver, spleen and intestine. Using histopathological and molecular diagnosis we detected Mycobacterium avium subsp. avium, etiological agent of avian tuberculosis. Further studies are needed to understand the role of wild birds in the persistence and transmission of thispathogen

Accessing Chiral Pyrrolodiketopiperazines under Organocatalytic Conditions

The production of chiral pyrrolodiketopiperazines under organocatalytic conditions demonstrates the capacity of bicyclic acylpyrrol lactims to perform as pronucleophiles in direct carbon–carbon bond forming reactions. The good performance of ureidoaminal-derived Brønsted bases in the Michael addition to nitroolefins affords these heterocyclic scaffolds with high skeleton diversity.Financial support was provided for the University of the Basque Country UPV/EHU (UFIQOSYC 11/22), the Basque Government (grant IT-1236-19), and Ministerio de Ciencia e Innovation (grant PID2019-109633GB-C21), Spain. E.D. thanks MICINN for a fellowship. We also thank SGiker (UPV/EHU) for providing NMR spectroscopy, HRMS, X-ray, and computational resources