Strategic Study on the Development of Space Science in China and Proposals for Future Missions

Since 2011,the Chinese Academy of Sciences(CAS)has implemented the Strategic Priority Program on Space Science(SPP).A series of scientific satellites have been developed and launched,such as Dark Matter Particle Explorer(DAMPE),Quantum Experiments at Space Scale(QUESS),Advanced Space-based Solar Observatory(ASO-S),Einstein Probe(EP),and significant scientific outcomes have been achieved.In order to plan the future space science missions in China,CAS has organized the Chinese space science community to conduct medium and long-term development strategy studies,and summarized the major scientific frontiers of space science as“One Black,Two Dark,Three Origins and Five Characterizations”.Five main scientific themes have been identified for China’s future breakthroughs,including the Extreme Universe,Space-Time Ripples,the Panoramic View of the Sun and Earth,the Habitable Planets,and Biological&Physical Science in Space.Space science satellite missions to be implemented before 2030 are proposed accordingly.

A guidance strategy for rendezvous and docking to the space station in the Earth-Moon NRHO orbit

With the development of space technology,it is possible to build a space station in Earth-Moon space as a transit for Earth-Moon round-trip and entering in the deep space.Rendezvous and docking is one of the key technologies for building an Earth-Moon space station.A guidance strategy for rendezvous and docking from the Earth orbit to the space station in the Earth-Moon NRHO orbit is proposed in this paper,which is suitable for engineering applications.Firstly,the rendezvous and docking process is divided into three sections,i.e.,the large-range orbit transfer section,far-range guidance section,and close-range approaching section.The suitable terminal of large-range orbit transfer is selected according to the eigenvalue of NRHO orbit state transition matrix.The two-impulse guidance method based on the relative motion equation in the three-body problem is adopted for the far-range guidance section.The impulse time and amplitude are solved with the optimization algorithm.The linear constant three-body relative motion equation is proposed for the close-range approaching section,and the rendezvous and docking is completed by a two-stage linear approximation.Finally,a simulation analysis is carried out,and the simulation results show that the adopted dynamics equations and the designed guidance law are effective,and the three flight phases are naturally connected to accomplish the rendezvous and docking mission from the Earth orbit to the space station on the Earth-Moon NRHO.

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.

Space station short-term mission planning using ontology modelling and time iteration

This paper studies the problem of the space station short-term mission planning, which aims to allocate the executing time of missions effectively, schedule the corresponding resources reasonably and arrange the time of the astronauts properly. A domain model is developed by using the ontology theory to describe the concepts, constraints and relations of the planning domain formally, abstractly and normatively. A method based on time iteration is adopted to solve the short-term planning problem. Meanwhile, the resolving strategies are proposed to resolve different kinds of conflicts induced by the constraints of power, heat, resource, astronaut and relationship. The proposed approach is evaluated in a test case with fifteen missions, thirteen resources and three astronauts. The results show that the developed domain ontology model is reasonable, and the time iteration method using the proposed resolving strategies can successfully obtain the plan satisfying all considered constraints.

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.

Spatio-Temporal Polar-Inclined Space Mission Architecture for a Refined Retrieve of the Earth’s Gravity Field

Future satellite gravity missions (FGMs) have been intensively studied during the last recent years for the era beyond the successful previous GRACE and current GRACE Follow-on satellite missions. Previous studies have investigated the gravity field recovery derived from combined two satellite-pairs (referred here as PI-FGM, a single polar satellite-pair like the GRACE mission combined with another inclined satellite-pair) with different orbital heights of few kilometers and different repeat orbital periods. In this contribution, new innovative idea is introduced by designing the inclined satellite-pair of the FGM at the same orbital height of the polar-type with shifted spatio-temporal (ST-FGM) orbital parameters to avoid any possible collision risk between the two satellite-pairs, polar and inclined, of the FGM architecture. The repeat orbits issue will be taken into consideration through the manuscript and will be set as identical as possible for a fair comparison. The findings through a full-scale simulation analysis show that the new design of shifted spatio-temporal polar-inclined (ST-FGM) mission architecture basically outperforms the two satellite-pairs having different orbital heights (i.e. the PI-FGM mission configuration). Regarding the gravity field recovery, the ST-FGM architecture retrieves the geoid heights with standard deviations of about 17.0 mm providing more isotropic error distribution. An overall improvement by a factor of about 80 and 60 is provided by the ST-FGM and PI-FGM mission architectures, respectively, with respect to the GRACE-like formation and a factor of about 2.4 and 1.8, respectively, with respect to the smoothed gravity solution using the Gaussian filter at radius 400 km. Therefore, the shifted spatio-temporal polar-inclined (ST-FGM) is worthy recommended as stable mission architecture and would be considered as one of the future gravity missions.

High Reliability LM-2F Launch Vehicle for Space Station Mission

As China’s only manned launch vehicle,the LM-2 F Launch vehicle successfully launched the Shenzhou 12 manned spacecraft into its predetermined orbit on June 12,2021,signifying the successful completion of the first manned launch mission in the construction and key technology test stage of China Space Station(CSS).From the launch of the Shenzhou 11 manned spacecraft on October 12,2016 to the launch of Shenzhou 12 in 2021,over the past five years,the LM-2 F launch vehicle has been continuously improved in terms of product reliability through technological innovation and design improvement,and its flight reliability index has increased from 0.97 to 0.98.Based on the new launch mission requirements for the construction stage of CSS,this paper introduces the technological innovation and reliability improvement methods of the LM-2 F from the aspects of design improvement,research methods and process optimization.The LM-2 F launch vehicle will make greater contributions in supporting the construction of CSS with higher reliability and perfect launch success rate.

Latest Scientific Results of China's Lunar and Deep Space Exploration(2022–2024)

China has successfully launched six lunar probes so far.From Chang'E-1 to Chang'E-4,they completed the circling,landing and roving exploration,of which Chang'E-4 was the first landing on the far side of the Moon in human history.Chang'E-5 was launched in December 2020,bringing back 1731 g of lunar soil samples.Through the detailed analysis of the samples,the scientists understand the history of late lunar volcanism,specifically extending lunar volcanism by about 800 million to 1 billion years,and proposed possible mechanisms.In addition,there are many new understandings of space weathering such as meteorite impacts and solar wind radiation on the Moon.China's first Mars exploration mission Tianwen-1 was successfully launched in July 2021.Through the study of scientific data,a number of important scientific achievements have been made in the topography,water environment and shallow surface structure of Mars.This paper introduces the main scientific achievements of Chang'E-4,Chang'E-5 and Tianwen-1 in the past two years,excluding technical and engineering contents.Due to the large number of articles involved,this paper only introduces part of the results.

China’s Space Science Satellite Series-A Review and Future Perspective

The National Space Science Center of the Chinese Academy of Sciences(NSSC,CAS),as the leading institute responsible for the overall management of scientific satellite missions in China,is China’s gateway to space science.NSSC is the cradle of China’s first artificial satellite“Dongfanghong-1”(DFH-1).In the course of more than 60 years’development,NSSC has led the implementation of“Double Star Program”,the first science-driven space mission in China,and successively implemented a fleet of scientific missions under the Strategic Priority Program on Space Science(Phase I and II),such as the Dark Matter Particle Explorer(DAMPE,or Wukong),the Quantum Experiments at Space Scale(QUESS,or Micius),the Hard X-ray Modulation Telescope(HXMT,or Insight),the Taiji-1,the Advanced space-based Solar Observatory(ASO-S,or Kuafu)and the Einstein Probe(EP).Currently,the space science satellite series has been established,yielding substantial scientific output.For the future,the Solar wind Magnetosphere Ionosphere Link Explorer(SMILE),a China-ESA joint mission,will be launched in 2025.In addition,the newly released National Mid-and Long-term Program for Space Science Development in China(2024-2050),the first of its kind at the national level,has identified five key scientific themes.A fleet of future scientific missions revolving these themes will deepen mankind’s scientific understanding of the universe.

Progress of Solar Wind Magnetosphere Ionosphere Link Explorer(SMILE) Mission

SMILE(Solar wind Magnetosphere Ionosphere Link Explorer) mission is a joint ESA-CAS space science project. The working orbit is a 19 Re 5000 km HEO with 4 scientific instruments: Soft X-ray Imager(SXI), Ultra-Violet Imager(UVI), Magnetometer(MAG) and Light Ion Analyzer(LIA). SMILE aims to understand the interaction between the solar wind and the Earth's magnetosphere through the images of SXI and UVI and in-situ measurement from LIA and MAG. After the kick-off in 2016, the SMILE project went to Phase A study. The mission adoption is scheduled for November 2018, with a target launch date in 2022–2023.In this paper, the background of the mission, scientific objectives, the design and characteristics of scientific instruments and the mission outline will be introduced in details.

KuaFu Mission

The KuaFu mission-Space Storms,Aurora and Space Weather Explorer-is an"L1+Polar"triple satellite project composed of three spacecraft:KuaFu-A will be located at L1 and have instruments to observe solar EUV and FUV emissions,and white-light Coronal Mass Ejections(CMEs),and to measure radio waves,the local plasma and magnetic field,and high-energy particles.KuaFuB1 and KuaFu-B2 will bein polar orbits chosen to facilitate continuous 24 hours a day observation of the north polar Aurora Oval.The KuaFu mission is designed to observe the complete chain of disturbances from the solar atmosphere to geospace,including solar flares,CMEs,interplanetary clouds,shock waves,and their geo-effects,such as magnetospheric sub-storms and magnetic storms,and auroral activities.The mission may start at the next solar maximum(launch in about 2012),and with an initial mission lifetime of two to three years.KuaFu data will be used for the scientific study of space weather phenomena,and will be used for space weather monitoring and forecast purposes.The overall mission design,instrument complement,and incorporation of recent technologies will target new fundamental science,advance our understanding of the physical processes underlying space weather,and raise the standard of end-to-end monitoring of the Sun-Earth system.

Progress and Prospects of the Strategic Priority Program on Space Science

In May 2018,the second phase of the Strategic Priority Program on Space Science(SPP II)was officially approved by the Chinese Academy of Sciences,in view of the significant scientific achievements of the first phase of the Strategic Priority Program on Space Science(SPP I)which includes 4 space science missions:the Dark Matter Particle Explorer(DAMPE),ShiJian-10(SJ-10),Quantum Experiments at Space Scale(QUESS)and Hard X-ray Modulation Telescope(HXMT).Aiming to address fundamental scientific questions,SPP II focuses on two major themes:How the universe and life originate and evolve and What is the relationship between the solar system and human beings.In areas that Chinese scientists have advantages,new space science missions including Graviational wave high-energy Electromagnetic Counterpart All-sky Monitor(GECAM),the Advanced space-based Solar Observatory(ASO-S),the Einstein Probe(EP),and Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)have been approved in the framework of SPP II.This paper presents the research highlights of the SPP I,introduces the recent progress of SPP II,and puts forward the prospects for future development.

Coupled Dynamics and Integrated Control for Position and Attitude Motions of Spacecraft:A Survey

Inspired by the integrated guidance and control design for endo-atmospheric aircraft,the integrated position and attitude control of spacecraft has attracted increasing attention and gradually induced a wide variety of study results in last over two decades,fully incorporating control requirements and actuator characteristics of space missions.This paper presents a novel and comprehensive survey to the coupled position and attitude motions of spacecraft from the perspective of dynamics and control.To this end,a systematic analysis is firstly conducted in details to show the position and attitude mutual couplings of spacecraft.Particularly,in terms of the time discrepancy between spacecraft position and attitude motions,space missions can be categorized into two types:space proximity operation and space orbital maneuver.Based on this classification,the studies on the coupled dynamic modeling and the integrated control design for position and attitude motions of spacecraft are sequentially summarized and analyzed.On the one hand,various coupled position and dynamic formulations of spacecraft based on various mathematical tools are reviewed and compared from five aspects,including mission applicability,modeling simplicity,physical clearance,information matching and expansibility.On the other hand,the development of the integrated position and attitude control of spacecraft is analyzed for two space missions,and especially,five distinctive development trends are captured for space operation missions.Finally,insightful prospects on future development of the integrated position and attitude control technology of spacecraft are proposed,pointing out current primary technical issues and possible feasible solutions.

China's Space Science Program(2025-2030):Strategic Priority Program on Space Science(Ⅲ)

The Strategic Priority Program(SPP)on Space Science,which is under the leadership of the Chinese Academy of Sciences(CAS),has established China’s space science satellite series from scratch.A number of major scientific achievements have been made by the first phase of the Program(SPPⅠ),while SPPⅡhas been currently being implemented.The future development of space science needs urgent top-level planning and advanced layout to clarify the overall goal and investment portfolio from 2025 to 2030.We will briefly introduce the initiative and possible space science missions of SPPⅢ,including the preparatory work which already started in July 2021.Following the effective administrative tradition since SPPⅠ,National Space Science Center(NSSC,CAS)is responsible for the whole procedure,including soliciting,assessment,and implementation of SPPⅢ.Brief information on the 13 candidate missions will be described,including missions in the fields of astronomy&astrophysics,exoplanets,heliophysics and planetary&Earth science,respectively.

Estimation of far-field wavefront error of tilt-to-length distortion coupling in space-based gravitational wave detection

In space-based gravitational wave detection, the estimation of far-field wavefront error of the distorted beam is the precondition for the noise reduction. Zernike polynomials are used to describe the wavefront error of the transmitted distorted beam. The propagation of a laser beam between two telescope apertures is calculated numerically. Far-field wavefront error is estimated with the absolute height of the peak-to-valley phase deviation between the distorted Gaussian beam and a reference distortion-free Gaussian beam. The results show that the pointing jitter is strongly related to the wavefront error. Furthermore, when the jitter decreases 10 times from 100 nrad to 10 nrad, the wavefront error reduces for more than an order of magnitude. In the analysis of multi-parameter minimization, the minimum of wavefront error tends to Z[5,3] Zernike in some parameter ranges. Some Zernikes have a strong correlation with the wavefront error of the received beam. When the aperture diameter increases at Z[5,3] Zernike, the wavefront error is not monotonic and has oscillation.Nevertheless, the wavefront error almost remains constant with the arm length increasing from 10-1Mkm to 10~3Mkm.When the arm length decreases for three orders of magnitude from 10-1Mkm to 10-4Mkm, the wavefront error has only an order of magnitude increasing. In the range of 10-4Mkm to 10~3Mkm, the lowest limit of the wavefront error is from 0.5 fm to 0.015 fm at Z[5,3] Zernike and 10 nrad jitter.

The CSES Mission and Its Preliminary Results

As the first satellite of the China national geophysical field observation series of stllite missions,the China Seismo--Electromagnetic Satellite(CSES)was designed upon an optimized CAST2000 platform for a sun synchronous orbit.Onboard CSES,there are total eight types of scientific payloads including the Search-coil Magnetometer,Electric Field Detector,High Precision Magnetometer,GNSS Occupation Receiver,Plasma Analyzer,Langmuir Probe,Energetic Particle Detector Package,and a Three-band Transmitter to individually acquire the global eletromagnetic field,elec-tromagnetic waves,ionospheric plasma parameters as well as energetic particles.Up to now,CSES has been operating normally in orbit for 2 years.By using the various sensor data acquired by CSES,we have achieved scientfic research in the areas of the global geomagnetic field modeling,space weather,earthquake event analysis,the Lithosphere-Atmo-sphere-lonosphere coupling mechanism and so on..

A Novel Magnetic Configuration for Space Radiation Active Shielding

Space radiation has been identified as the main health hazard to crews involved in manned Mars missions.Active shielding is more effective than passive shielding to the very energetic particles from cosmic rays.Particle motion in a magnetic field is studied based on the single-particle theory and Monte Carlo method.By comparing the shielding efficiency of different magnetic field configurations,a novel active magnetic shielding configuration with lower mass cost and power consumption is proposed for manned Mars missions.The new magnetic configuration can shield 92.8%of protons and 84.4%of alpha particles with E<4 GeV·n^(-1),when considering the passive shielding contribution of 10.0 g·cm^(-2) Al Shielding,the required magnetic stiffness can be reduced from 27 Tm to 16 Tm.The detailed analysis of mass cost and power consumption shows that active shielding will be a promising means to protect crews from space radiation exposure in manned Mars missions.

Current Status and Main Scientific Outcomes of the CSES Mission

This report briefly introduces the current status of the CSES(China Seismo-Electromagnetic Satellite)mission which includes the first satellite CSES 01 in-orbit(launched in February 2018),and the second satellite CSES 02(will be launched in 2023)under development.The CSES 01 has been steadily operating in orbit for over four years,providing abundant global geophysical field data,including the background geomagnetic field,the electromagnetic field and wave,the plasma(in-situ and profile data),and the energetic particles in the ionosphere.The CSES 01 platform and the scientific instruments generally perform well.The data validation and calibration are vital for CSES 01,for it aims to monitor earthquakes by extracting the very weak seismic precursors from a relatively disturbing space electromagnetic environment.For this purpose,we are paying specific efforts to validate data quality comprehensively.From the CSES 01 observations,we have obtained many scientific results on the ionosphere electromagnetic environment,the seismo-ionospheric disturbance phenomena,the space weather process,and the Lithosphere-Atmosphere-Ionosphere coupling mechanism.

Space Solar Physics in China:2020-2022

To follow up the last report two years ago,what happened from 2020 to 2022 deserves specially mentioning:CHASE was successfully launched on 14 October 2021;ASO-S will finish soon its Phase-D study and is scheduled for launch in October 2022;four solar mission candidates are being undertaken the engineering project evaluations;three solar mission proposals are being undertaken the background project evaluations;there are also quite a number of pre-study space solar physics projects getting either newly supported or finished.This paper describes in brief the status of all these related projects.

Retrospect to Human Deep Space Exploration History and Its Prospect in China

The definition, goal and impacts of deep space exploration are summarized. After a retrospect to past deep exploration activities of human being to date, both recent deep space missions and future missions in 5 years are also listed. There are also brief introductions about the future strategic plans of NASA, ESA, RAKA, JAXA and ISRO. Then authors analyze some important features of global deep space exploration scheme. Key technologies of deep space exploration are also determined. The status of China deep exploration plan is introduced including CE-1 lunar orbiter, the subsequent China Lunar Exploration Program, especially proposal for the second stage of China Lunar Exploration Program, Mars exploration program of China with Russia Kuafu mission, Hard X-Ray Modulated Telescope, Space Solar Telescope. At the end, some suggestions for China future deep space exploration are made.