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21.
Michael Dellnitz Oliver Junge Marcus Post Bianca Thiere 《Celestial Mechanics and Dynamical Astronomy》2006,95(1-4):357-370
Recently new techniques for the design of energy efficient trajectories for space missions have been proposed that are based on the circular restricted three body problem as the underlying mathematical model. These techniques exploit the structure and geometry of certain invariant sets and associated invariant manifolds in phase space to systematically construct energy efficient flight paths. In this paper, we extend this model in order to account for a continuously applied control force on the spacecraft as realized by certain low thrust propulsion systems. We show how the techniques for the trajectory design can be suitably augmented and compute approximations to trajectories for a mission to Venus. 相似文献
22.
Due to the existence of invariant tori, chaotic sea and hyperbolic structures in higher dimensional phase space of a volume-preserving
map, the diffusion route of chaotic orbits will be complicated. The velocity of diffusion will be very slow if the orbits
are near an invariant torus. In order to realize this complicated diffusion phenomenon, in this paper we study the diffusion
characters in the different regions, i.e., chaotic, hyperbolic and invariant tori's regions. We find that for the three different
regions, the diffusion velocities are different. The diffusion velocity in the vicinity of an invariant torus is the slowest
one.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
23.
We assess the accuracy of some indirect approaches to invariant point (IVP), or system reference point, determination of satellite
laser ranging (SLR) and very long baseline interferometry (VLBI) systems using both observed and simulated survey data sets.
Indirect IVP determination involves the observation of targets located on these systems during specific rotational sequences
and by application of geometrical models that describe the target motion during these sequences. Of concern is that most SLR
and VLBI systems have limited rotational freedom thereby placing constraint on the reliability of parameter estimation, including
the IVP position. We assess two current approaches to IVP analysis using survey data observed at the Yarragadee (Australia)
SLR and the Medicina (Italy) VLBI sites and also simulated data of a large rotationally constrained (azimuth-elevation) VLBI
system. To improve reliability we introduce and assess some new geometric conditions, including inter-axis, inter-circle and
inter-target conditions, to existing IVP analysis strategies. The error component of a local tie specifically associated with
the indirect determination of SLR and VLBI IVP is less than 0.5 mm. For systems with significant rotational limits we find
that the inter-axis and inter-circle conditions are critical to the computation of unbiased IVP coordinates at the sub-millimetre
level. When the inter-axis and inter-circle geometric conditions are not imposed, we retrieve biased vertical coordinates
of the IVP (in our simulated VLBI system) in the range of 1.2–3.4 mm. Using the new geometric conditions we also find that
the axis-offset estimates can be recovered at the sub- millimetre accuracy (0.5 mm). 相似文献