Astrodynamics最新文献

Large spacecraft fall out of orbit and re-enter the atmosphere at the end of their lifetime, and they can break up into small debris upon re-entry. The spacecraft debris generated by the disintegration may lead to high risk when the surviving debris reaches the ground. One way to reduce the damage risk of spacecraft is to simulate the spacecraft disintegration process and accurately predict the falling area. Aerodynamics seriously affects the reentering process, especially in the continuous flow regime. Aerodynamic force and heat are the main factors leading to debris disintegration. High dynamic pressure leads to sharp changes in attitude and complex trajectories during debris fall. A numerical method based on an unstructured Cartesian grid was developed to simulate the disintegrating separation problem by coupling the Navier-Stokes equation and the six-degree-of-freedom trajectory equation. A method combining the numerical method for dynamic processes with numerical simulation based on a static aerodynamic/dynamic characteristic database was developed for forecasting the falling area. Spacecraft disintegrating separation from 60 km was simulated using the method, and the multibody aerodynamic interference and the separation trajectory were predicted. The falling process was forecast by a numerical simulation method based on the static aerodynamic database/dynamic characteristic database when the debris went out of the influence domain. This method has good forecasting efficiency while considering the aerodynamic interference, making it a valuable method for forecasting disintegrating separation and falling debris.

Currently, a surge in the number of spacecraft and fragments is observed, leading to more frequent breakup events in low Earth orbits (LEOs). The causes of these events are being identified, and specific triggers, such as collisions or explosions, are being examined for their importance to space traffic management. Backward propagation methods were employed to trace the origins of these types of breakup events. Simulations were conducted using the NASA standard breakup model, and satellite Hitomi’s breakup was analyzed. Kullback-Leibler (KL) divergences, Euclidean 2-norms, and Jensen-Shannon (JS) divergences were computed to deduce potential types of breakups and the associated fragmentation masses. In the simulated case, a discrepancy of 22.12 s between the estimated and actual time was noted. Additionally, the breakup of the Hitomi satellite was estimated to have occurred around UTC 1:49:26.4 on March 26, 2016. This contrasts with the epoch provided by the Joint Space Operation Center, which was estimated to be at 1:42 UTC ± 11 min. From the findings, it was suggested that the techniques introduced in the study can be effectively used to trace the origins of short-term breakup events and to deduce the types of collisions and fragmentation masses under certain conditions.

As an emerging approach to space situational awareness and space imaging, the practical use of an event-based camera (EBC) in space imaging for precise source analysis is still in its infancy. The nature of event-based space imaging and data collection needs to be further explored to develop more effective event-based space imaging systems and advance the capabilities of event-based tracking systems with improved target measurement models. Moreover, for event measurements to be meaningful, a framework must be investigated for EBC calibration to project events from pixel array coordinates in the image plane to coordinates in a target resident space object’s reference frame. In this paper, the traditional techniques of conventional astronomy are reconsidered to properly utilise the EBC for space imaging and space situational awareness. This paper presents the techniques and systems used for calibrating an EBC for reliable and accurate measurement acquisition. These techniques are vital in building event-based space imaging systems capable of real-world space situational awareness tasks. By calibrating sources detected using the EBC, the spatiotemporal characteristics of detected sources or “event sources” can be related to the photometric characteristics of the underlying astrophysical objects. Finally, these characteristics are analysed to establish a foundation for principled processing and observing techniques which appropriately exploit the capabilities of the EBC.

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.