New celestial assisted INS initial alignment method for lunar explorer

In the future lunar exploration programs of China, soft landing, sampling and returning will be realized. For lunar explorers such as Rovers, Landers and Ascenders, the inertial navigation system （INS） will be used to obtain high-precision navigation information. INS propagates position, velocity and attitude by integration of sensed accelerations, so initial alignment is needed before INS can work properly. However, traditional ground-based initial alignment methods cannot work well on the lunar surface because of its low rotation rate （0.55°/h）. For solving this problem, a new autonomous INS initial alignment method assisted by celestial observations is proposed, which uses star observations to help INS estimate its attitude, gyroscopes drifts and accelerometer biases. Simulations show that this new method can not only speed up alignment, but also improve the alignment accuracy. Furthermore, the impact factors such as initial conditions, accuracy of INS sensors, and accuracy of star sensor on alignment accuracy are analyzed in details, which provide guidance for the engineering applications of this method. This method could be a promising and attractive solution for lunar explorer＇s initial alignment.

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.

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.

国际月球科研站

As the closest celestial body to the Earth, the moon is a hot spot for international space science research at present. Countries around the world have conducted lunar exploration time after time, among which, China’s Lunar Exploration Program has achieved 6 consecutive successful lunar missions. China has made a series of significant achievements in deep space exploration, and its cooperation with international partners is increasingly strengthened. In order to gather global space power and scientists’ wisdom, the International lunar Research Station(ILRS) is proposed by China and will be jointly constructed by many countries, which will be equipped with the support capabilities of energy supply, central control, communications and navigation, space-Earth round-trip transportation, lunar surface scientific research, and ground support. All international partners are encouraged to jointly develop and build the ILRS, and to jointly initiate the establishment of the International Lunar Research Station Cooperation Organization(ILRSCO) to achieve the long-term effective, operation and management of the station. The vast universe sparks the exploration dream of humankind, so let’s set sail together.

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.

Development and calibration of the Moon-based EUV camera for Chang'e-3

The process of development and calibration for the first Moon-based ex- treme ultraviolet （EUV） camera to observe Earth＇s plasmasphere is introduced and the design, test and calibration results are presented. The EUV camera is composed of a multilayer film mirror, a thin film filter, a photon-counting imaging detector, a mech- anism that can adjust the direction in two dimensions, a protective cover, an electronic unit and a thermal control unit. The center wavelength of the EUV camera is 30.2 nm with a bandwidth of 4.6nm. The field of view is 14.7° with an angular resolution of 0.08°, and the sensitivity of the camera is 0.11 count s-1 Rayleigh-1. The geomet- ric calibration, the absolute photometric calibration and the relative photometric cal- ibration are carried out under different temperatures before launch to obtain a matrix that can correct geometric distortion and a matrix for relative photometric correction, which are used for in-orbit correction of the images to ensure their accuracy.

Development of High-energy Particle Detectors for Space Exploration

Space environment exploration is a hot topic globally.The scope of space exploration ranges from near-Earth space to the moon,other planets in the solar system,and even the heliosphere and interplanetary space.It is used for various crucial applications,including aerospace technology development,space weather research,understanding the origin and evolution of the universe,searching for extraterrestrial life,and finding human livable places.Although China’s space environment exploration started late,its progress has been rapid.China is gradually narrowing the gap with advanced countries and may eventually lead the world in space research.This article briefly reviews the development history of China’s space environmental detectors.

Innovative developments in lunar and planetary science promoted by China's lunar exploration

As the only natural satellite of the earth, the Moon has always been the first choice for human exploration of the solar system. China's lunar exploration project(Chang'e project) was launched in 2004. At present, it has created a perfect end to the three phases of “orbiting, landing and returning”. A series of remarkable research achievements have been made on the basic issues of current lunar scientific research, such as the Earth-Moon space environment, lunar surface material, morphology,geological structure, lunar subsurface and internal structure, and the origin and evolution of the Moon, further deepening the human understanding of the Moon. This paper briefly reviews the development process of China's lunar exploration project,summarizes the main research results and scientific understanding, and finally prospects to the future development of China's lunar and planetary exploration.

月球探测与开发愿景

By summarizing the history,human achievements in lunar exploration,the vision and prospect of the con-strucion of a lunar base for the further development in lunar exploration is proposed.The idea of building a"beehive"lunar vllage is proposed,and the promotion of future lunar exploration along with the impact on the development of science,technology and the economy is analyzed in this paper。

Scheme design of the CHANG＇E-5T1 extended mission

Flight schemes for the CHANG＇E-5T1 extended mission are investigated in this paper.In the flight scheme and trajectory design, the remaining propellant of the CHANG＇E-5T1 mission is utilized. The CHANG＇E-5T1 mission is firstly introduced with feasible flight goals derived based on the terminal trajectory and satellite status. The flight schemes are designed to include a lunar return and the libration points in the Sun-Earth/Moon and Earth-Moon systems, with an emphasis on the Earth-Moon triangle libration point thus far unexplored. Secondly, three schemes are proposed for the CHANG＇E-5T1 extended mission with different flight goals. The direct libration point orbit transfer and injection method is adopted to solve the issue in the transfer trajectory design.Furthermore, an innovative concept is proposed to transfer from the Earth-Moon collinear libration point to the triangle point using the Sun-Earth/Moon libration point. Finally, the merits and drawbacks of the three schemes are discussed in terms of flight time, control energy and frequency, flight distance, and goal value. As a result, the scheme including a lunar return and the Earth-Moon L2 libration point is selected for the CHANG＇E-5T1 extended mission. A flight to the Earth-Moon libration point is achieved, replicating the achievement of the ARTEMIS mission.

Management innovation of Chang'e-5 project

1 Overview of Chang'e-5 project As the final step of the"three-step''development strategy(i.e.,orbiting,landing and sample returning)of the Chinese Lunar Exploration Program,the Chang,e-5 project aims to achieve moon surface sampling and retrieving for the first time in China.It was initiated with the approval of the State Council in January 2011.

Landing control method of a lightweight four-legged landing and walking robot

The prober with an immovable lander and a movable rover is commonly used to explore the Moon’s surface.The rover can complete the detection on relatively flat terrain of the lunar surface well,but its detection efficiency on deep craters and mountains is relatively low due to the difficulties of reaching such places.A lightweight four-legged landing and walking robot called“FLLWR”is designed in this study.It can take off and land repeatedly between any two sites wherever on deep craters,mountains or other challenging landforms that are difficult to reach by direct ground movement.The robot integrates the functions of a lander and a rover,including folding,deploying,repetitive landing,and walking.A landing control method via compliance control is proposed to solve the critical problem of impact energy dissipation to realize buffer landing.Repetitive landing experiments on a five-degree-of-freedom lunar gravity testing platform are performed.Under the landing conditions with a vertical velocity of 2.1 m/s and a loading weight of 140 kg,the torque safety margin is 10.3%and 16.7%,and the height safety margin is 36.4%and 50.1%for the cases with or without an additional horizontal disturbance velocity of 0.4 m/s,respectively.The study provides a novel insight into the next-generation lunar exploration equipment.