The PCA Rules for dispute settlement in outer space: A significant step forward

Outer space activities have evolved significantly. While they were previously the exclusive domain of a restricted number of states, now thanks to technological advances and the easing of governmental restrictions, space activities are carried out on a much larger scale and involve subjects of both a governmental and non-governmental nature. Furthermore, the commercial uses of outer space are making space business increasingly profitable and attractive to potential investors. As the economic value of outer space activities, as well as the number of space actors grows, it is nearly inevitable that international disputes related to the use of outer space will occur. Until recently, international space law contained little dedicated machinery to settle international outer space-related disputes. This absence significantly weakened the applicability and enforceability of space law and contributed to a climate of uncertainty. In order to address these issues, the Permanent Court of Arbitration (PCA) adopted the Optional Rules for Arbitration of Disputes Relating to Outer Space Activities on 6 December 2011. The PCA Space Rules represent a significant development in the field of space law because they provide a voluntary and binding dispute settlement method accessible to all space actors and modeled on the specific legal and economic characteristics of space activities. This paper describes the genesis of the PCA Space Rules, assesses their content and innovative character, evaluates their possible implications for the settlement of outer space disputes, and argues that they should be positively received by the outer space community.     

Uncertainties in gravity wave parameters,momentum fluxes,and flux divergences estimated from multi-layer measurements of mesospheric nightglow layers

Measurements of dynamic parameters of atmospheric gravity waves, mainly the vertical wavelength, the momentum flux and the momentum flux divergence, are affected by large uncertainties crudely documented in the scientific literature. By using methods of error analysis, we have quantified these uncertainties for frequently observed temporal and spatial wave scales. The results show uncertainties of ～10%, ～35%, and ～65%, at least, in the vertical wavelength, momentum flux, and flux divergence, respectively. The large uncertainties in the momentum flux and flux divergence are dominated by uncertainties in the Brunt-Väisälä frequency and in spatial separation of the nightglow layers, respectively. The measured uncertainties in fundamental wave parameters such as the wave amplitude, intrinsic period, horizontal wavelength, and wave orientation are ～10% or less and estimated directly from our nightglow image data set. Other key environmental quantities such as the scale height and the Brunt-Väisälä frequency, frequently considered as constants in gravity wave parameter estimations schemes, are actually quite variable, presenting uncertainties of ～4% and ～9%, respectively, according to the several solar activity and seasonal atmosphere scenarios from the NRLMSISE-00 model simulated here.     

A genetic algorithm for Initial Orbit Determination from a too short arc optical observation

Optical observations constitute a source of angular measurements of a satellite pass. Commonly, these observations have short durations with respect to the satellite orbit period. As a consequence, the use of classical orbit determination algorithms, as Laplace, Gauss or Escobal methods, give very poor results. The present work faces with the problem of estimating the orbital parameters of an orbiting object using its optical streak acquired by a telescope or a high accuracy camera. In the paper a new technique is developed for the Initial Orbit Determination from optical data by exploiting the genetic algorithms. The algorithm works without restrictions on the observer location. A recent challenging problem is the Initial Orbit Determination with space-based observations. This work focuses on the problem of determinating the orbital parameters of a satellite from an orbiting observer in LEO, using short time observations. We present the results based on a simulation with the observer on a sun-synchronous orbit with a single observation of just 60 s. Monte Carlo simulations are presented with different levels of sensor accuracy to show the reliability of the algorithm. The algorithm is able to yield a candidate solution for each observation. The coplanar case is analyzed and discussed as well.