The output torque estimation of MCMG for agile satellites

Studied in this paper are the attitude control law design and the output torque estimation problem of micro control moment gyros （MCMGs） for the agile satellites executing rapid attitude maneuver mission. An algorithm is proposed for estimating the output torques and the gimbal angular rates of MCMGs, which can help engineers to choose reasonable size for actuators so that the cost of satellite can be decreased. According to some special maneuver missions, a numerical example of attitude control system for a small satellite with MCMGs in pyramid configuration is studied, and the simulation results validate the proposed estimation algorithm.

Cutting-Edge Space Exploration Technology Maturity Level Facilitation with Support of Space Debris Removal Missions

Considering current space debris situation in outer space environment,different methods for debris removal missions are proposed.In addition,advanced technologies are needed to be demonstrated for future human space exploration programs.The main issue regarding to these missions is high mission cost for both debris removal missions and space environmental tests to achieve high maturity level for new space-usable technologies.Since,these missions are unavoidable for future of human space activities,a solution which can tackle these challenges is necessary.This paper will address to an idea which has the possibility to give a solution for facilitating technology readiness level(TRL)maturity tests by debris removal mission platform consideration.

On-orbit target tracking and inspection by satellite formation

A new type of estimator is developed for the satellite formation to track and inspect on-orbit targets. The follower satellite in the formation works without relative sensors, and its target pointing commands are derived based on relative orbital dynamics. The centralized estimator based on truth measurement is designed, however, this estimator is proved unstable because of the lack of necessary measurement information. After that, an alternative estimator based on pseudo measurement is designed, and its observability and controllability are analyzed to qualitatively evaluate the convergence performance. Finally, an on-orbit target inspection scenario is numerically simulated to verify the performance of the estimator based on pseudo measurement.

Target sequence optimization for multiple debris rendezvous using low thrust based on characteristics of SSO

A method is proposed to select the target sequence for a J 2-perturbed multiple debris rendezvous mission aimed at removing dozens of debris from several thousand debris candidates running on sun-synchronous orbits(SSO).The solving methodology proceeds in two steps:Firstly,the variance of the right ascension of ascending node(RAAN)of the debris group is used for narrowing down the potential debris candidate;secondly,the debris of the candidate group that has closest RAAN to the current debris is chosen as the next debris.The low thrust near-minimum-fuel trajectories of each rendezvous leg are obtained by the indirect optimization method.The proposed approach is demonstrated for the problem of the 8th China Trajectory Optimization Competition(CTOC).The radar cross section(RCS)of the debris is also considered in the first step since the primary performance index of the competition is to maximize the total RCS of the debris visited.The results show that the proposed approach achieves better performance within a competition period.Of the many rendezvous sequences found,the best one submitted for the competition obtained a total RCS of 184 by accomplishing rendezvous with 70 debris within a transfer duration of one year.

LEO Mega Constellations:Review of Development,Impact,Surveillance,and Governance

The rapid development of Low Earth Orbit(LEO)mega constellations has significantly contributed to several aspects of human scientific progress,such as communication,navigation,and remote sensing.However,unrestrained deployment of constellations has also strained orbital resources and increased spacecraft congestion in LEO,which seriously affects the safety of in-orbit operations of many space assets.For the long-term and sustainable development of space activities in LEO regions,space environment stability must be maintained using more rational surveillance and governance mechanisms.This review contributes to the research gap and facilitates the development of LEO mega constellations.First,the current development of typical LEO mega constellations is reviewed,followed by the analysis of the impact of LEO mega constellations in terms of astronomical observation,spacecraft safety in orbit,and space environment evolution.Then,two main solutions to conduct the challenges raised by LEO mage constellations are elaborated:one is to ensure the safety operation of spacecraft using space surveillance infrastructures and space situational awareness technologies,and the other is to accelerate the deorbit of constellation satellites at the end of life based on postmission disposal and active removal methods.Finally,the future development and potential research directions of LEO mega constellations are prospected.