Legal rules aimed at compensation for the harm caused by a particular state, individual, or legal entity (for example, oil pollution of the sea due to a tanker accident) are well studied and constantly used in scientific literature and international law practice. Meanwhile, every year, the number of cases of harm when the particular guilty party cannot be established grows; this is why it is almost impossible to compensate for the harm caused. Such cases include collisions of satellites causing space debris; the consequences of climate change for agriculture, forestry, and the health of citizens; and the pollution of the World Ocean with plastic debris, ballast water, and abandoned nets.

There are more such cases at the national level. After studying acts of international environmental law, national legislation, and several examples from judicial practice, we show that compensation for the harm caused to life, health, or property in the absence of a particular harm-doer is difficult or impossible to prove. This is why actions that can prevent subjectless environmental harm are taken at the national level in certain countries by developing measures to mitigate and adapt to climate change, licensing space activities, and taking preventive measures against the formation of plastic debris and its pollution of the seas, etc. This trend should be continued, and the experience gained by certain states should be used in developing new acts of international environmental law. This will ensure the next step towards preventing environmental harm where it is impossible to establish the doer’s name.

The quantity of man-made space objects, ranging from abandoned launch vehicle stages to fragmentation debris, is remarkable. At the time, the drafters of the Outer Space Treaty did not (and perhaps could not) anticipate how great the problem of debris in outer space would one day become. As a result, they only drafted general provisions for the protection of the space environment which are generally deemed insufficient. This article aims to demonstrate that both general rules of international law and the UNCOPUOS Debris Mitigation Guidelines come to the rescue in addressing the space debris issue as they complement and complete the general obligations contained in the Outer Space Treaty. Particular attention is paid to anti-satellite weapon tests, which have catastrophic consequences in terms of creating debris but nonetheless continue to be carried out. Finally, it ascertains whether an obligation on states to actively remove their space debris exists.

We present a software package for single-dish data processing of spacecraft signals observed with VLBI-equipped radio telescopes. The Spacecraft Doppler tracking (SDtracker) software allows one to obtain topocentric frequency detections with a sub-Hz precision and reconstructed and residual phases of the carrier signal of any spacecraft or landing vehicle at any location in the Solar System. These data products are estimated using the ground-based telescope’s highly stable oscillator as a reference, without requiring an a priori model of the spacecraft dynamics nor the downlink transmission carrier frequency. The software has been extensively validated in multiple observing campaigns of various deep space missions and is compatible with the raw sample data acquired by any standard VLBI radio telescope worldwide. In this paper, we report the numerical methodology of SDtracker, the technical operations for deployment and usage, and a summary of use cases and scientific results produced since its initial release.

Orbiting objects in space are exposed to the risk of collision with space debris over their lifetime. Space debris orbiting in space experiences orbital decay due to various orbital perturbations. This work considers only orbital perturbations due to aerodynamic forces, which spacecraft experience due to the presence of a rarefied atmosphere, causing tumbling motion and orbital decay. Analysis of the orbital decay of a spacecraft is carried out by considering the variation of the drag coefficient as a function of its shape, motion and angle-of-attack. An in-house Direct Simulation Monte Carlo (DSMC) solver is modified for aerodynamic analysis of a spacecraft orbiting in the free molecular regime in low Earth orbit. In addition, an orbital dynamics model is developed to simulate the tumbling motion of a spacecraft and its orbital decay. The orbital decay trajectory is predicted for two sample spacecrafts using the aerodynamic coefficients obtained from the in-house DSMC solver as inputs to the orbital decay model. This study analyses and explores in detail the effects of the aerodynamic coefficients and shape of a spacecraft on its orbital decay.

The European Space Operations Centre currently operates five Copernicus Sentinel satellites in the framework of Europe’s Copernicus Earth observation programme. The routine operations rely on a daily orbit determination, carried out on-ground, consisting in a least-squares fit of a dynamical model to GPS navigation solutions generated on-board. The purpose of this paper is the estimation of realistic uncertainties on this daily determined state vector. By comparison with the orbit derived by Precise Orbit Determination, we estimate the 1-sigma errors at approximately 0.5m and 0.5mm/s. Non-stationary errors in the navigation solution preclude their characterisation with a constant covariance matrix. Error whitening is achieved by decreasing the signal-to-noise ratio in the errors through the use of underestimated weights on the data. The approach keeps the errors on the derived state vector unchanged and allows the covariance on the state vector to become realistic.

The RemoveDEBRIS mission has been the first mission to successfully demonstrate, in-orbit, a series of technologies that can be used for the active removal of space debris. The mission started late in 2014 and was sponsored by a grant from the EC that saw a consortium led by the Surrey Space Centre to develop the mission, from concept to in-orbit demonstrations, that terminated in March 2019. Technologies for the capture of large space debris, like a net and a harpoon, have been successfully tested together with hardware and software to retrieve data on non-cooperative target debris kinematics from observations carried out with on board cameras. The final demonstration consisted of the deployment of a drag-sail to increase the drag of the satellite to accelerate its demise.

Normal form methods allow one to compute quasi-invariants of a Hamiltonian system, which are referred to as proper elements. The computation of the proper elements turns out to be useful to associate dynamical properties that lead to identify families of space debris, as it was done in the past for families of asteroids. In particular, through proper elements we are able to group fragments generated by the same break-up event and we possibly associate them to a parent body. A qualitative analysis of the results is given by the computation of the Pearson correlation coefficient and the probability of the Kolmogorov-Smirnov statistical test.

The future space debris environment will be dominated by the production of fragments coming from massive fragmentations. In order to identify the most relevant parameters influencing the long term evolution of the environment and to assess the criticality of selected space objects in different regions of the circumterrestrial space, a large parametric study was performed. In this framework some indicators were produced to quantify and rank the relevance of selected fragmentations on the long term evolution of the space debris population. Based on the results of the fragmentation studies, a novel analytic index, the Criticality of Spacecraft Index, aimed at ranking the environmental criticality of abandoned objects in LEO, has been devised and tested on a sample population of orbiting objects.

We advertise a new method of preliminary orbit determination for space debris using radar observations, which we call Infang†. We can perform a linkage of two sets of four observations collected at close times. The context is characterized by the accuracy of the range ρ, whereas the right ascension α and the declination δ are much more inaccurate due to observational errors. This method can correct α, δ, assuming the exact knowledge of the range ρ. Considering no perturbations from the J2 effect, but including errors in the observations, we can compare the new method, the classical method of Gibbs, and the more recent Keplerian integrals method. The development of Infang is still on-going and will be further improved and tested.

The joint observations of space debris are conducted by NAO and SHAO. The main task of observations is precise estimation of the hazard collisions of SD with operating satellites. Observations of the near earth asteroids (NEA) on the distance of less than 0.05 AU, according to the NEODyS program, are conducted in NAO. The main task is to obtain the large number of precise observations of the NEAs during their closest approach to the Earth.

This study is based on the definition of the admissible region introduced by Milani et al.(2004); in the search for potential Earth impactors, this theory allows to take into account the partial data of the TSA (Too Short Arcs) from which it is impossible to deduce a full orbit. Only a set of 4 variables (two angles and their instantaneous time derivatives), called an attributable, is known; a few suitable boundary conditions allow to restrict the motions to a specific bounded 2-dimensional region. In this work, a new inner boundary of this region is introduced, based on the geocentric hyperbolic motion of the immediate impactors; the nodal distances (crossings of the virtual asteroidal orbits with the Earth's orbit) are drawn for two different test attributables, associated with a determination of circular and linear orbits. This could reduce the search for impactors (by propagation of the orbits) to a one-dimensional set. A few comments about elongations and complementary curves complete this paper.