Self-induced collision risk of the Starlink constellation based on long-term orbital evolution analysis

The deployment of mega constellations has had a significant effect on the compounding space debris environment,increasing the number of on-orbit objects in all conditions and damaging the stability of the space debris environment.The increased density of space objects is associated with an increased risk of on-orbit collisions.Collision risk exists not only between a mega constellation and the space debris environment but also inside a mega constellation.In this study,we used the Starlink constellation to investigate the self-induced collision risk caused by malfunctioning satellites.First,we analyzed the conjunction condition between malfunctioning and operative satellites based on long-term orbital evolution characteristics.The collision probability was then calculated based on the conjunction analysis results.The results show that malfunctioning satellites in Phase 1 cause an 86.2%self-induced collision probability based on a malfunctioning rate of 1%,which is close to the collision probability caused by objects larger than 6 cm during five years of service.Therefore,self-induced collisions are another important risk factor for the Starlink constellation.

New Long-Term Climate Oscillations

The astronomical theory of climate change is based on the solution of differential equations describing Earth’s orbital and rotational motions. The equations are used to calculate the change in insolation over the Earth’s surface. As a result of the author’s solution of the orbital problem, the periods and amplitudes of Earth-orbit variations and their evolution have been refined. Unlike previous studies, the equations of Earth’s rotational motion are solved completely. The Earth’s rotational axis precesses relative to a direction different from the direction of the orbit’s axial precession, and oscillates with periods of half a month, half a year and 18.6 years. Also, its oscillations occur with irregular periods of several tens of thousands of years and more. All these motions lead to oscillations of the obliquity in the range of 14.7° to 32.1°, which prove to be 7 - 8 times larger than obtained by a previous theory. In the same proportion, the Earth’s insolation oscillations increase in amplitude, with insolation extremes occurring in other epochs than those in the previous theory. The amplitudes and the onset times of the extremes correlate with known paleoclimate changes. Thirteen insolation periods of paleoclimate variation over an interval of 200 thousand years are identified. From the insolation evolution calculated over a time interval of 1 million years, 6 climate gradations from very cold to very warm are identified.