Constellations of elliptical inclined lunar orbits providing polar and global coverage

Abstract

Prior results have developed a methodology for selecting a long-lived constellation of three satellites that provide persistent, stable coverage to either the North or South Pole with no requirement for stationkeeping under the influence of only gravitational perturbations. In the present study, the sensitivity of this coverage in the presence of nongravitational forces is determined, and a design strategy is formulated that minimizes any potential sensitivity to these accelerations. The class of orbits and methods are extended to the search for global coverage constellations of six satellites. Two constellations are designed that provide 99.999% global coverage for a ten-year period also without the need for any deterministic orbit maintenance.

Generating Solar Sail Trajectories in the Earth-Moon System Using Augmented Finite-Difference Methods

“…To generate the magnitude of the sail acceleration in dimensional units, a 0 , β is multiplied by the system characteristic acceleration, a * , which is the relationship between the dimensional and nondimensional acceleration in (1). In fact, a * is the ratio of the characteristic length, L * (384,400 km for the Earth-Moon distance), to the square of the characteristic time, t * (2πt * = 27.321 days), that is,…”

“…The sparsity pattern for the FDM-R formulation is similar to that of the FDM-RV, except that the diagonal The advantage of a finite-difference approach is its ease of implementation and the speed improvements enabled by its simplicity. Partial derivatives are easily accessible via analytical derivation, especially for an idealized force model such as (1). As complexity of the formulation increases, which is the case with collocation, for example, analysts rely on numerical or automatic differentiation to generate partial derivatives.…”

“…A leading candidate location for the lunar base is at the south pole, which is not always in view of either antennas on the Earth or space-based transceivers, such as the TDRSS satellites, in geosynchronous orbit. Therefore, at least two spacecraft in traditional polar orbits about the Moon are required for an Earth-Moon link [1].…”

Terrain-Relative and Beacon-Relative Navigation for Lunar Powered Descent and Landing

“…Three-body gravitational disturbances from the earth are the biggest concern for high-altitude lunar orbits, such as those necessary for an effective global lunar network with a minimal number of satellites. In cases with high inclinations, these three-body perturbations can mutate a circular orbit into a near-parabolic orbit within a few years' time [3,13]. Care must be taken to determine stable orbits with inclinations high enough to provide constant coverage of the poles.…”

“…Care must be taken to determine stable orbits with inclinations high enough to provide constant coverage of the poles. Todd Ely presents a method by which a highly-inclined frozen orbit can be designed such that it remains boundedly stable in the presence of both gravitational [14] and solar pressure [13] disturbances without the need for deterministic orbit maintenance.…”