Dynamic access task scheduling of LEO constellation based on space-based distributed computing

A dynamic multi-beam resource allocation algorithm for large low Earth orbit(LEO)constellation based on on-board distributed computing is proposed in this paper.The allocation is a combinatorial optimization process under a series of complex constraints,which is important for enhancing the matching between resources and requirements.A complex algorithm is not available because that the LEO on-board resources is limi-ted.The proposed genetic algorithm(GA)based on two-dimen-sional individual model and uncorrelated single paternal inheri-tance method is designed to support distributed computation to enhance the feasibility of on-board application.A distributed system composed of eight embedded devices is built to verify the algorithm.A typical scenario is built in the system to evalu-ate the resource allocation process,algorithm mathematical model,trigger strategy,and distributed computation architec-ture.According to the simulation and measurement results,the proposed algorithm can provide an allocation result for more than 1500 tasks in 14 s and the success rate is more than 91%in a typical scene.The response time is decreased by 40%com-pared with the conditional GA.

China's National Space Science Programs(2006-2010)

1 Introduction Looking back to the 20th century, the science and technology have never influenced and changed all aspects of the people's lives as profoundly as they do today. With the birth of space technology in late 1950s, space science emerged accompanying the space activities as a unique comprehensive discipline. Mankind started exploring various natural phenomenon and their laws in space by use of innovative spacecraft to reveal the mysteries of the universe. The space science research provides theoretical basis for mankind to understand the universe and develop application technologies, and drives the development of high and new technologies.……

China’s Lunar and Deep Space Exploration Program for the Next Decade(2020–2030)

China has carried out four unmanned missions to the Moon since it launched Chang’E-1,the first lunar orbiter in 2007.With the implementation of the Chang’E-5 mission this year,the three phases of the lunar exploration program,namely orbiting,landing and returning,have been completed.In the plan of follow-up unmanned lunar exploration missions,it is planned to establish an experimental lunar research station at the lunar south pole by 2030 through the implementation of several missions,laying a foundation for the establishment of practical lunar research station in the future.China successfully launched its first Mars probe on 23 July 2020,followed in future by an asteroid mission,second Mars mission,and a mission to explore Jupiter and its moons.

Space Debris Research Progress of China

The rapid increase of space debris population has posed serious threaten to the safety of human space activities and became a global issue.How to enhance the technical capabilities of space debris threat coping ability is of great significance to the sustainable development of space activities,the further development,and utilization of outer space.In this paper,we describe space debris research progress of China on observation,collision avoidance,protection,mitigation,regulation,and standard during the last twenty years,and look forward to the future development direction of space debris.

A Brief Introduction to the International Lunar Research Station Program and the Interstellar Express Mission

China has planned and implemented a series of lunar and deep space exploration programs since the first lunar exploration satellite Chang’E-1 launched in 2007.In the future,China has initiated the international lunar research station program,which aims to build a shared platform on the Moon jointly with many other countries for long-term and continuous lunar exploration,lunar-based observations and experiments,as well as in-situ resource utilization.In addition,China has also proposed an interstellar express mission to unveil the mysteries of the outer heliosphere,nearby interstellar space,and their interactions.This paper gives a brief introduction to the International Lunar Research Station program and the Interstellar Express mission.

Particle swarm optimization based space debris surveillance network scheduling

The increasing number of space debris has created an orbital debris environment that poses increasing impact risks to existing space systems and human space flights. For the safety of in-orbit spacecrafts, we should optimally schedule surveillance tasks for the existing facilities to allocate re- sources in a manner that most significantly improves the ability to predict and detect events involving affected spacecrafts. This paper analyzes two criteria that mainly affect the performance of a scheduling scheme and introduces an artificial intelligence algorithm into the scheduling of tasks of the space debris surveillance network. A new scheduling algorithm based on the particle swarm optimization algorithm is proposed, which can be implemented in two different ways： individual optimization and joint optimiza- tion. Numerical experiments with multiple facilities and objects are conducted based on the proposed algorithm, and simulation results have demonstrated the effectiveness of the proposed algorithm.

Impulsive orbit control for spacecraft around asteroid

An impulse feedback control law to change the mean orbit elements of spacecraft around asteroid is presented. First, the mean orbit elements are transferred to the osculating orbit elements at the burning time. Then, the feedback control law based on Gauss’s perturbation equations of motion is given. And the impulse control for targeting from the higher circulation orbit to the specified periapsis is developed. Finally, the numerical simulation is performed and the simulation results show that the presented impulse control law is effective.

Timeline based autonomous mission planning system for deep space exploration

In order to realize the explorer autonomy, the software architecture of autonomous mission management system (AMMS) is given for the deep space explorer, and the autonomous mission planning system, the kernel part of this architecture, is designed in detail. In order to describe the parallel activity, the state timeline is introduced to build the formal model of the planning system and based on this model, the temporal constraint satisfaction planning algorithm is proposed to produce the explorer’s activity sequence. With some key subsystems of the deep space explorer as examples, the autonomous mission planning simulation system is designed. The results show that this system can calculate the executable activity sequence with the given mission goals and initial state of the explorer.

Eleventh Five-Year Plan for Space Science Development

Preface Space science is a discipline to study the universe,to investigate the fundamental process of molecules and atoms,and reveal,at the underlying roots,the laws of the external world.

A Morphological Study of Two Young Multipolar Planetary Nebulae

We carry out an optical morphological and infrared spectral study for two young planetary nebulae(PNs)Hen2-158 and Pe 1-1 to understand their complex shapes and dust properties.Hubble Space Telescope optical images reveal that these nebulae have several bipolar-lobed structures and a faint arc with a clear boundary is located at the northwestern side of Pe 1-1.The presence of this arc-shaped structure suggests that the object interacts with its nearby interstellar medium.Spitzer IRS spectroscopic observations of these young nebulae clearly show prominent unidentified infrared emission features and a weak silicate band in Pe 1-1,indicating that Hen 2-158 is a carbonrich nebula and Pe 1-1 has a mixed chemistry dust environment.Furthermore,we construct two three-dimensional models for these PNs to realize their intrinsic structures.The simulated models of the nebulae suggest that multipolar nebulae may be more numerous than we thought.Our analyses of spectral energy distributions for Hen 2-158 and Pe 1-1 show that they have low luminosities and low stellar effective temperatures,suggesting that these nebulae are young PNs.A possible correlation between typical multipolar young PNs and nested nebulae is also discussed.

中国的深空探测

At present,the moon and Mars are the main focus of deep space exploration,scientific pursuits are the initial goal,and extensive cooperation leads to a greater prospect.China has made many scientific achievements and built considerable infrastructure through its lunar and Mars exploration activities.In the future,China will continue to carry out deep space exploration activities with scientific goals as the driving force,develop the International Lunar Research Station,explore the sun,inner planets and asteroids,discover exoplanets and build an asteroid defence system.In order to support future deep space exploration missions,China will construct an integrated communication,navigation and remote sensing constellation and develop heavy-lift launch vehicles.China offers a wide range of opportunities for cooperation,upholds the central role of Committee on the Peaceful Uses of Outer Space(UNCOPUOS),and welcomes all countries in the world to participate in deep space exploration activities.

Design of MGA trajectories for main belt asteroid

Asteroid exploration is one of the most sophisticated missions currently being investigated. Gravity-assist trajectories have proven valuable in interplanetary missions such as the Pioneer, Voyager and Galileo. In this paper, we design interplanetary trajectory for main belt asteroid exploration mission with the Mars gravity-assist (MGA) using “pork chop” plots and patched-conic theory and give some initial valuable trajectory parameters on main belt asteroid exploration mission with MGA.

Ivar asteroid rendezvous mission system scenario and trajectory design

The asteroid exploration opportunities are searched and calculated with launch dates in 2006 to2010, and with asteroid Ivar 1627 as the target, the spacecraft and its subsystems are designed and analyzed,and the transfer trajectory is designed using △VEGA technology for the asteroid rendezvous. The design resultssatisfied the energy requirements for small explorers.

Autonomous determination of orbit for probe around asteroids using unscented Kalman filter

The observed images of the asteroid and the asteroid reference images are used to obtain the probe-to-asteroid direction and the location of the limb features of the asteroid in the inertial coordinate. These informa-tion in combination with the shape model of the asteroid and attitude information of the probe are utilized to ob-tain the position of the probe. The position information is then input to the UKF which determines the real-timeorbit of the probe. Finally, the autonomous orbit determination algorithm is validated using digital simulation.The determination of orbit using UKF is compared with that using extended Kalman filter (EKF), and the resultshows that UKF is superior to EKF.

Groove formation on Phobos from reimpacting orbital ejecta of the Stickney crater

Numerous linear grooves have long been recognized as covering the surface of Phobos, but the mechanisms of their formation are still unclear. One possible mechanism is related to the largest crater on Phobos, the Stickney crater, whose impact ejecta may slide,roll, bounce, and engrave groove-like features on Phobos. When the launch velocity is higher than the escape velocity, the impact ejecta can escape Phobos. A portion of these high-velocity ejecta are dragged by the gravitational force of Mars, fall back, and reimpact Phobos.In this research, we numerically test the hypothesis that the orbital ejecta of the Stickney crater that reimpact Phobos could be responsible for a particular subset of the observed grooves on Phobos. We adopt impact hydrocode i SALE-2 D(impact-Simplified Arbitrary Lagrangian Eulerian, two-dimensional) to simulate the formation of the Stickney crater and track its impact ejecta, with a focus on orbital ejecta with launch velocities greater than the escape velocity of Phobos. The launch velocity distribution of the ejecta particles is then used to calculate their trajectories in space and determine their fates. For orbital ejecta reimpacting Phobos, we then apply the sliding boulder model to calculate the ejecta paths, which are compared with the observed groove distribution and length to search for causal relationships. Our ejecta trajectory calculations suggest that only ~1% of the orbital ejecta from the Stickney crater can reimpact Phobos. Applying the sliding boulder model, we predict ejecta sliding paths of 9-20 km in a westward direction to the east of the zone of avoidance, closely matching the observed grooves in that region. The best-fit model assumes an ejecta radius of ~150 m and a speed restitution coefficient of 0.3, consistent with the expected ejecta and regolith properties. Our calculations thus suggest the groove class located to the east of the zone of avoidance may have been caused by reimpact orbital ejecta from the Stickney crater.

Autonomous planning system based on temporal constraint satisfaction

In order to realize spacecraft autonomy activity duration and complex temporal relations must be taken into consideration. In the space mission planning system, the traditional planners are unable to describe this knowledge, so an object-oriented temporal knowledge representation method is proposed to model every activity as an object to describe the activity's duration, start-time, end-time and the temporal relations with other activities. The layered planning agent architecture is then designed for spacecraft autonomous operation, and the functions of every component are given. A planning algorithm based on the temporal constraint satisfaction is built in detail using this knowledge representation and system architecture. The prototype of Deep Space Mission Autonomous Planning System is implemented. The results show that with the object-oriented temporal knowledge description method, the space mission planning system can be used to describe simultaneous activities, resource and temporal constraints, and produce a complete plan for exploration mission quickly under complex constraints.

Seamless maps of major elements of the Moon:Results from high-resolution geostationary satellite

Major elements such as Fe,Ti,Mg,Al,Ca and Si play very important roles in understanding the origin and evolution of the Moon.Previous maps of these major elements derived from orbital data are based on mosaic images or low-resolution gamma-ray data.The hue variations and gaps among orbital boundaries in the mosaic images are not conducive to geological studies.This paper aims to produce seamless and homogenous distribution maps of major elements using the single-exposure image of the whole lunar disk obtained by China’s high-resolution geostationary satellite,Gaofen-4,with a spatial resolution of500 m.The elemental contents of soil samples returned by Apollo and Luna missions are regarded as ground truth,and are correlated with the reflectance of the sampling sites extracted from Gaofen-4 data.The final distribution maps of these major oxides are generated with the statistical regression model.With these products,the average contents and proportions of the major elements for maria and highlands were estimated and compared.The results showed that Si O2 and Ti O2 have the highest and lowest fractions in mare and highland areas,respectively.Moreover,the relative concentrations of these elements could serve as indicators of geologic processes,e.g.,the obviously asymmetric distributions of Al2 O3,Ca O and Si O2 around Tycho crater may suggest that Tycho crater was formed by an oblique impact from the southwest direction.

The Present Situation And Future Development Of Chang'e Program

The first lunar orbiter of China＇s Chang＇e Program will be launched in 2007. The lunar orbiting project, the first phase of Chang＇e Program, includes five major engineering systems. Three engineering objectives and four scientific objectives will be realized during the first phase. This paper gives a brief introduction to the present situation and future development of Chang＇e Program.

Research of Lunar Water-Ice and Exploration for China’s Future Lunar Water-Ice Exploration

Since the 1990s,the existence of water-ice in the permanent shadow areas of the lunar polar regions and the problem of water in the early lunar period have become the hot spot of international lunar exploration.This paper analyzes the research progress and existing problems of lunar water-ice detection in recent years.Based on the analysis of expected foreign lunar water-ice exploration missions,the major scientific problems of lunar water-ice are analyzed.From different exploration methods,this paper tentatively puts forward the scientific tasks,payload configuration,functional requirements,and possible scientific outputs of water-ice in China's future lunar exploration projects,which can provide reference for future lunar exploration missions.

Interplanetary transfers employing invariant manifolds and gravity assist between periodic orbits

The interest in the periodic orbits of the restricted three-body problem continues to grow for their significant practical application.This paper focuses on the interplanetary transfers between periodic orbits of two different three-body systems,whose invariant manifolds have no intersection in phase space.A novel design method is proposed to obtain the optimal transfer employing the invariant manifolds and planetary gravity assist.The periapsis Poincare map is used to analyze the periapsides of invariant manifolds.On the basis of hyperbola approximation,the impulses performed on the periapsis of invariant manifolds are calculated with a simple iterative algorithm.The propellant-efficient escape and capture trajectories can be found by comparing the impulses magnitudes corresponding to different invariant manifolds,which can provide the appropriate initial guess for optimization.Further,the trajectory design is formulated as an unconstrained optimization problem under the perturbed restricted three-body model.An efficient algorithm combining simplex method and differential correction is adopted to obtain the optimal solution.The validity of the proposed approach is demonstrated through several interplanetary low energy transfer trajectories.