Pulsar searching is an important frontier in radio astronomy. Weaker signals can be received as the performance of search facilities continualy improved. However，how to accurately identify the suspected pulsar signal from massive candidates has become a challenge. The pulsar candidate classification methods about development history and current situation at home and abroad. The classification methods in each stage include：manual selection methods and machine learning methods. At last，the future development trends are analyzed.
In order to improve the spacecraft capability of autonomous celestial navigation，a celestial Doppler difference/pulsar for formation flying and its integrated navigation method is proposed. The Sun light is strong，and the accuracy of the Sun Doppler difference navigation is high，but it is difficult to provide multi-directional velocity information. Star light is weak，and the accuracy of star Doppler difference navigation is low，but it can provide multi-directional velocity information. The Sun Doppler difference navigation and the star Doppler difference navigation are complementary，but which cannot be fully observable. Using three or more pulsar navigation is completely observable，but the filtering period is longer，and it is difficult to obtain continuous navigation information. The three navigation methods are complementary and can be used for integrated navigation. The extended Kalman filter is used as a navigation filter to fuse the difference and arrival time of the astronomical Doppler，and can provide absolute and relative navigation information for formation flying. Simulation results show that the integrated navigation method for formation flight can provide absolute and relative highly-accurate navigation information.
The X-ray pulsar data processing methods and procedures are introduced. The X-ray basic data format，X-ray original data processing，time analysis，spectrum analysis are described. X-ray data processing are conducted，taking the NASA X-ray detection mission NuSTAR and，some preliminary results are provided. This paper provides a reference for the scholar entering the pulsar navigation and astronomy research field.
In order to verify the real-time and applicability of the X-ray pulsar navigation algorithm in the space-borne computer environment，an of the X-ray pulsar navigation prototype based on the FPGA + DSP architecture is designed. The FPGA in the navigation prototype is used for logic control and photon data storage. The DSP is used to convert the received photon data，pulse folding，pulse data inter correlation processing，data interpolation and least squares filtering algorithm. A semi physical simulation platform for X-ray pulsars navigation is built to verify the prototype. The system uses residual error of TOA as observation quantity and combines orbital dynamics equation and filtering algorithm to realize navigation and positioning of spacecraft. The simulation results show that the position error is better than 10 km and the speed error is better than 1 km/s.
The X-ray pulsar-based navigation （XNAV） technology is to determine the attitude，position and velocity of spacecraft using X-ray signals emitted from pulsars. The feasibility and sustainability of pulsar navigation is invented through theoretical astrometric analyses. The processing and modeling of pulsar signals of both X-ray and radio band is introduced，and then investigate The key problems in pulsar navigation are analyzed，and finally the applicable range of distance of XNAV is discussed. The our analyses show that the acquiring of the measurements is highly influenced by the spacecraft velocity. With the error of less than 3 m/s，the profile of a pulsar signal can be got，and from which the time of arrival （TOA） could be obtained. Also，the phase cycle ambiguity is a non-negligible problem in pulsar navigation.
The first batch observation data of the X-ray pulsar-based navigation test satellite were released. We get 35 files of the time of the arrival of the photons using the standard basic astronomical program library proposed by International Astronomical Union and the JPL ephemerides. Using the method of epoch folding and the known ephemeris parameters，35 pulse integral profiles are obtained. The kernel regression method is used to reduce the noise. The influence of the folding bin number on time residual is analyzed. The results show that the observation data is effective，and the pulse integral profiles can be obtained，and the detection of crab star is realized. The kernel regression algorithm effectively reduces the effect of the bin number on the time residual. The rooted-mean-square of the pre-fit timing residual is about 40 μs.
Small celestial bodies are important carriers for humans to understand the origin and evolution of the Solar system，and they are also rich in precious metals and rare elements. Sampling exploration of small celestial bodies has a vital value for scientific development. The environment which has influence on sampling missions is concluded through the reserch of the surface characteristics of small celestial bodies and the existing sampling technology. The technology requirements of small celestial body samplers are summarized.
The ordinary CSP algorithms cannot reflect the characteristics of the task planning progress. How the action rules in task planning for deep space exploration can be mapped into the constraint satisfaction problems is discussed. Based on the conclusion，an action directed constraint is proposed to guide the variable selection procedure in constraint satisfaction problems. Through theoretical analysis，the proposed technology can be used in constraint-programmed planning problem. The simulation experiments show that the algorithm with action guided constraint can effectively reduce the number of constraint checks during the planning procedure and has a better performance on total running time over the standard version. It lays the foundation for the application of the project.
Mars Ascent Vehicle（MAV）design is closely related to trajectory design. However，the existing method mostly decoupled the staging optimization and trajectory optimization，resulting in computational inefficiency and poor robustness. A coupled staging-trajectory multiphase optimization algorithm is proposed in this paper for a two-stage MAV design. Considering given vehicle，mission，path and control constraints，the objective of the optimization algorithm is to minimize the Gross Lift-off Mass（GLOM）of the two-stage MAV，and the algorithm is based on Gauss pseudospectral method. By using this algorithm，an optimal staging design is obtained，and an optimal trajectory is designed to minimize propellant consumption simultaneously. And the algorithm solves the problem that trajectory optimization algorithm couldn’t converge due to the unreasonable MAV staging design. In addition，numerical simulations show that the coupled staging-trajectory multiphase optimization algorithm have good robustness and strong convergence.
Binary asteroid explorations are of great scientific significance. It is extremely challenging for exploring binary asteroids because of the complex dynamical environments. Spherical harmonics method is adopted to represent the gravitational field of the binary asteroid. Five equilibrium points of binary asteroid system are obtained. The inner collinear equilibrium point L1 is selected as the target point of the hovering flight. By considering the characteristic of impulsive thrusters, a kind of bang-bang controller which is simple and easily implemented for engineering operation is designed. This paper takes 69230 Hermes as an example, models it with two ellipsoids. Hovering flight over the point L1 of the binary asteroid Hermes is numerically simulated to verify the effectiveness of the proposed method.
Reliable and safe lunar landing and ascending is the basic condition for lunar exploration. It is also a key technology in the probe development，therefore ground test is required. As the environment on the ground are different from that on the moon，the operation features of the probe on the ground are also different. The design and the implement of the ground test are difficult. The design points of the lunar landing and ascending and the critical factors of the ground test are analyzed. The existing defects in current test technology are pointed out. A ground test verification scheme using the impetus of the probe itself for landing and ascending is proposed，and its feasibility is validated by the dynamic simulation. The extended application of the scheme is putted forward. The related research provides reference for the future development of Chinese lunar or planetary probes.
In this paper，a dielectric constant measurement system for powder materials is presented，which can work at different temperatures ranging from room temperature to 200 ℃.This system is developed based on the theory of NRW algorithm using coaxial line. There are two key design factors of this system. One is an improved calibration method to remove the adapter and pads. Another is the temperature distribution is analyzed and optimized using ANSYS thermal analysis to ensure the temperature is uniform in the test fixture and is safe enough to connect to the Vector Network Analyzer （VNA）. In this paper，the simulated lunar soil is measured from room temperature to 200 ℃，from1 GHz to 18 GHz. At different temperatures，the permittivity of simulated lunar soil LLB-07 and lunar soil JSC-1A is very similar. The dielectric constant and loss tangent of simulated lunar soil increase with the increase of temperature. The test system of this paper can be used to test the variable temperature permittivity of powder materials.
Cryogenic propellants are considered to be the most economic and efficient chemical propellant for the space entering and orbit transfer，due to its high specific impulse and non-pollution. And they are also the first choice of propellant for future human lunar exploration，Mars exploration，and deeper space exploration. Thermodynamic vent system（TVS）is the key technology for long-term on-orbit storage of cryogenic fuel. In present study，one ground experiment is established to investigate the pressure control performance of TVS. The simulant fluid HCFC123 is selected to be the experiment fluid and to verify the efficient of TVS in the ground. The tank pressure variation and fluid temperature change are respectively studied during the tank self-pressurization，the injection mixing depressurization and active refrigeration process. The refrigeration capacity supplied by the TVS heat exchanger and the thermal stratification during different phases are specially illustrated. The present experiment proves the effectiveness of the pressure control performance by means of TVS. When compared to the direct venting method，TVS has recovered more than 41% venting loss，which could provide references for the development of cryogenic propellant thermodynamic vent system.
