This paper addresses the challenges of insufficient navigation accuracy,low path-planning efficiency,and poor environmental adaptability faced by deep space rovers in complex extraterrestrial environments(e.g.,the Moo...This paper addresses the challenges of insufficient navigation accuracy,low path-planning efficiency,and poor environmental adaptability faced by deep space rovers in complex extraterrestrial environments(e.g.,the Moon and Mars).A novel autonomous navigation scheme is proposed that integrates laser Doppler velocimetry(LDV)with star trackers(ST)and inertial navigation system(INS).The scheme suppresses slip errors from wheel odometry through non-contact,high-precision laser speed measurement(accuracy better than 0.1%).By deeply fusing multi-source data via a Kalman filter algorithm,high-precision positioning is realized under extreme extraterrestrial conditions such as weak illumination and dust coverage.This solution features high accuracy,non-contact measurement,and anti-interference capabilities,significantly improving the navigation accuracy and autonomy of deep space rovers in complex environments.展开更多
With the expansion of the female player base and the increase in their purchasing power,the female-oriented game market has gradually risen.This paper employs the Uses and Gratifications Theory as a framework,using th...With the expansion of the female player base and the increase in their purchasing power,the female-oriented game market has gradually risen.This paper employs the Uses and Gratifications Theory as a framework,using the successful case of Love and Deep Space to explore how female players satisfy their specific social and psychological needs through gaming.The study finds that female-oriented games effectively meet the diverse needs of female players in terms of content design,interactive experiences,and community building,further promoting the prosperity and development of the female-oriented game market.展开更多
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 th...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.展开更多
Carrier tracking is laid great emphasis and is the difficulty of signal processing in deep space communication system.For the autonomous radio receiving system in deep space, the tracking of the received signal is aut...Carrier tracking is laid great emphasis and is the difficulty of signal processing in deep space communication system.For the autonomous radio receiving system in deep space, the tracking of the received signal is automatic when the signal to noise ratio（SNR） is unknown.If the frequency-locked loop（FLL） or the phase-locked loop（PLL） with fixed loop bandwidth, or Kalman filter with fixed noise variance is adopted, the accretion of estimation error and filter divergence may be caused.Therefore, the Kalman filter algorithm with adaptive capability is adopted to suppress filter divergence.Through analyzing the inadequacies of Sage–Husa adaptive filtering algorithm, this paper introduces a weighted adaptive filtering algorithm for autonomous radio.The introduced algorithm may resolve the defect of Sage–Husa adaptive filtering algorithm that the noise covariance matrix is negative definite in filtering process.In addition, the upper diagonal（UD） factorization and innovation adaptive control are used to reduce model estimation errors,suppress filter divergence and improve filtering accuracy.The simulation results indicate that compared with the Sage–Husa adaptive filtering algorithm, this algorithm has better capability to adapt to the loop, convergence performance and tracking accuracy, which contributes to the effective and accurate carrier tracking in low SNR environment, showing a better application prospect.展开更多
In consultative committee for space data systems（CCSDS） file delivery protocol（CFDP） recommendation of reliable transmission,there are no detail transmission procedure and delay calculation of prompted negative ac...In consultative committee for space data systems（CCSDS） file delivery protocol（CFDP） recommendation of reliable transmission,there are no detail transmission procedure and delay calculation of prompted negative acknowledge and asynchronous negative acknowledge models.CFDP is designed to provide data and storage management,story and forward,custody transfer and reliable end-to-end delivery over deep space characterized by huge latency,intermittent link,asymmetric bandwidth and big bit error rate（BER）.Four reliable transmission models are analyzed and an expected file-delivery time is calculated with different trans-mission rates,numbers and sizes of packet data units,BERs and frequencies of external events,etc.By comparison of four CFDP models,the requirement of BER for typical missions in deep space is obtained and rules of choosing CFDP models under different uplink state informations are given,which provides references for protocol models selection,utilization and modification.展开更多
Four future missions for deep space exploration and future space-based exoplanet surveys on habitable planets by 2030 are scheduled to be launched.Two Mars exploration missions are designed to investigate geological s...Four future missions for deep space exploration and future space-based exoplanet surveys on habitable planets by 2030 are scheduled to be launched.Two Mars exploration missions are designed to investigate geological structure,the material on Martian surface,and retrieve returned samples.The asteroids and main belt comet exploration is expected to explore two objects within 10 years.The small-body mission will aim to land on the asteroid and get samples return to Earth.The basic physical characteristics of the two objects will be obtained through the mission.The exploration of Jupiter system will characterize the environment of Jupiter and the four largest Moons and understand the atmosphere of Jupiter.In addition,we further introduce two space-based exoplanet survey by 2030,Miyin Program and Closeby Habitable Exoplanet Survey(CHES Mission).Miyin program aims to detect habitable exoplanets using interferometry,while CHES mission expects to discover habitable exoplanets orbiting FGK stars within 10 pc through astrometry.The above-mentioned missions are positively to achieve breakthroughs in the field of planetary science.展开更多
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 explorati...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.展开更多
Deep space communications has played an important role in deep space exploration. Compared with common satellite and terrestrial communications, deep space communications faces more challenging environment. The paper ...Deep space communications has played an important role in deep space exploration. Compared with common satellite and terrestrial communications, deep space communications faces more challenging environment. The paper investigated the unique features of deep space communica-tions in detail, discussed the key technologies and its development trends for deep space communica-tions.展开更多
The spacecraft for deep space exploration missions will face extreme environments,including cryogenic temperature,intense radiation,wide-range temperature variations and even the combination of conditions mentioned ab...The spacecraft for deep space exploration missions will face extreme environments,including cryogenic temperature,intense radiation,wide-range temperature variations and even the combination of conditions mentioned above.Harsh environments will lead to solder joints degradation or even failure,resulting in damage to onboard electronics.The research activities on high reliability solder joints using in extreme environments can not only reduce the use of onboard protection devices,but effectively improve the overall reliability of spacecraft,which is of great significance to the aviation industry.In this paper,we review the reliability research on SnPb solder alloys,Sn-based lead-free solder alloys and In-based solder alloys in extreme environments,and try to provide some suggestions for the follow-up studies,which focus on solder joint reliability under extreme environments.展开更多
Compared with common near space satellite Telemetry,Telecommand,and Communication(TT&C),deep space TT&C presents a more challenging environment such as long distance,very low Signal to Noise Ratio(SNR).How to ...Compared with common near space satellite Telemetry,Telecommand,and Communication(TT&C),deep space TT&C presents a more challenging environment such as long distance,very low Signal to Noise Ratio(SNR).How to acquire main carrier exactly becomes a hot focus for deep space communications.Already there emerged some main carrier acquisition algorithms,but they all require high SNR and small modulation index.In this paper,we develop a new acquire algorithm.First we use the spectral energy center algorithm to shorten the original sequence,filter out some noise and make the spectral more symmetric.Then we adopt the spectral symmetry algorithm to make full use of the whole spectrum information,and utilize FFT to reduce computation complexity.Simulation results show that our algorithm can acquire main carrier successfully under large modulation index and get good performance with low Carrier to Noise Ratio(CNR).展开更多
The footpad structure of a deep space exploration lander is a critical system that makes the initial contact with the ground,and thereby plays a crucial role in determining the stability and energy absorption characte...The footpad structure of a deep space exploration lander is a critical system that makes the initial contact with the ground,and thereby plays a crucial role in determining the stability and energy absorption characteristics during the impact process.The conventional footpad is typically designed with an aluminum honeycomb structure that dissipates energy through plastic deformation.Nevertheless,its effectiveness in providing cushioning and energy absorption becomes significantly compromised when the structure is crushed,rendering it unusable for reusable landers in the future.This study presents a methodology for designing and evaluating structural energy absorption systems incorporating recoverable strain constraints of shape memory alloys(SMA).The topological configuration of the energy absorbing structure is derived using an equivalent static load method(ESL),and three lightweight footpad designs featuring honeycomb-like Ni-Ti shape memory alloys structures and having variable stiffness skins are proposed.To verify the accuracy of the numerical modelling,a honeycomb-like structure subjected to compression load is modeled and then compared with experimental results.Moreover,the influence of the configurations and thickness distribution of the proposed structures on their energy absorption performance is comprehensively evaluated using finite element simulations.The results demonstrate that the proposed design approach effectively regulates the strain threshold to maintain the SMA within the constraint of maximum recoverable strain,resulting in a structural energy absorption capacity of 362 J/kg with a crushing force efficiency greater than 63%.展开更多
Digital fountain is applied into deep space communication for its rateless and non-feedback forward error correction.However,the long code length and encoding overhead are confined factors to guarantee a considerable ...Digital fountain is applied into deep space communication for its rateless and non-feedback forward error correction.However,the long code length and encoding overhead are confined factors to guarantee a considerable recovery probability as power and buffer-limited equipment in deep space environment.At the same time,the typical fountain decoding is sub-optimum decoding algorithm.We propose a new approach,Dependent Sequences Compensation Algorithm(DSCA),to improve the encoding efficiency by restricting the randomness in fountain encoding.While decoding algorithm is also optimized by redundant information in stopping set.The results show that the optimized method can obtain a 10-4 decoding failure rate with overhead under 0.20 for code length 500,which indicates the usefulness of the proposed approach in deep space communication.展开更多
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 ...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.展开更多
A deep space multi-file delivery protocol（DSMDP） based on LT codes is proposed to reduce the influence of long delay and a high bit error rate（BER） in deep space communication. The protocol increases sending redun...A deep space multi-file delivery protocol（DSMDP） based on LT codes is proposed to reduce the influence of long delay and a high bit error rate（BER） in deep space communication. The protocol increases sending redundancy by LT codes to improve the success rate of file delivery, and adopts different protective strategies for different situations of packet loss. At the same time, the multi-file united delivery strategy is adopted to make full use of the retransmission time to reduce the end-toend transmission delay. Furthermore, the protocol determines the quantity of encoded packets according to the feedback for controlling redundancy. The simulation results show that the proposed protocol can significantly reduce the transmission delay of files, which would be effectively suitable for deep space communication environment of high BER and long delay.展开更多
With the development of science, economy and society, the needs for research and exploration of deep space have entered a rapid and stable development stage. Deep Space Optical Network(DSON) is expected to become an i...With the development of science, economy and society, the needs for research and exploration of deep space have entered a rapid and stable development stage. Deep Space Optical Network(DSON) is expected to become an important foundation and inevitable development trend of future deepspace communication. In this paper, we design a deep space node model which is capable of combining the space division multiplexing with frequency division multiplexing. Furthermore, we propose the directional flooding routing algorithm(DFRA) for DSON based on our node model. This scheme selectively forwards the data packets in the routing, so that the energy consumption can be reduced effectively because only a portion of nodes will participate the flooding routing. Simulation results show that, compared with traditional flooding routing algorithm(TFRA), the DFRA can avoid the non-directional and blind transmission. Therefore, the energy consumption in message routing will be reduced and the lifespan of DSON can also be prolonged effectively. Although the complexity of routing implementation is slightly increased compared with TFRA, the energy of nodes can be saved and the transmission rate is obviously improved in DFRA. Thus the overall performance of DSON can be significantly improved.展开更多
A reasonable parameter configuration helps improve the data transmission performance of the Licklider Transmission Protocol(LTP).Previous research has focused mainly on parameter optimization for LTP in simplified sce...A reasonable parameter configuration helps improve the data transmission performance of the Licklider Transmission Protocol(LTP).Previous research has focused mainly on parameter optimization for LTP in simplified scenarios with one to two hops or multihop scenarios with a custody mechanism of the Bundle Protocol(BP).However,the research results are not applicable to communications in Complex Deep Space Networks(CDSNs)without the custody mechanism of BP that are more suitable for deep space communications with LTP.In this paper,we propose a model of file delivery time for LTP in CDSNs.Based on the model,we propose a Parameter Optimization Design Algorithm for LTP(LTP-PODA)of configuring reasonable parameters for LTP.The results show that the accuracy of the proposed model is at least 6.47%higher than that of the previously established models based on simple scenarios,and the proposed model is more suitable for CDSNs.Moreover,the LTP parameters are optimized by the LTP-PODA algorithm to obtain an optimization plan.Configuring the optimization plan for LTP improves the protocol transmission performance by at least 18.77%compared with configuring the other parameter configuration plans.展开更多
A major limitation for deep space communication is the limited bandwidths available. The downlinkrate using X-band with an L2 halo orbit is estimated to be of only 5.35 GB/d. However, the Next GenerationSpace Telescop...A major limitation for deep space communication is the limited bandwidths available. The downlinkrate using X-band with an L2 halo orbit is estimated to be of only 5.35 GB/d. However, the Next GenerationSpace Telescope (NGST) will produce about 600 GB/d. Clearly the volume of data to downlink must be re-duced by at least a factor of 100. One of the resolutions is to encode the data using very low bit rate image com-pression techniques. An very low bit rate image compression method based on region of interest(ROI) has beenproposed for deep space image. The conventional image compression algorithms which encode the original datawithout any data analysis can maintain very good details and haven' t high compression rate while the modernimage compressions with semantic organization can have high compression rate even to be hundred and can' tmaintain too much details. The algorithms based on region of interest inheriting from the two previews algorithmshave good semantic features and high fidelity, and is therefore suitable for applications at a low bit rate. Theproposed method extracts the region of interest by texture analysis after wavelet transform and gains optimal localquality with bit rate control. The Result shows that our method can maintain more details in ROI than generalimage compression algorithm(SPIHT) under the condition of sacrificing the quality of other uninterested areas.展开更多
In this paper, according to the AR4JA codes in deep space communication, two kinds of iterative decoding including partly parallel decoding and overlapped partly parallel decoding are analyzed, and the advantages and ...In this paper, according to the AR4JA codes in deep space communication, two kinds of iterative decoding including partly parallel decoding and overlapped partly parallel decoding are analyzed, and the advantages and disadvantages of them are listed. A modified overlapped partly parallel decoding that not only inherits the advantages of the two algorithms, but also overcomes the shortcomings of the two algorithms is proposed. The simulation results show that the three kinds of decoding have the same decoding performance; modified overlapped partly parallel decoding improves the iterative convergence rate and the throughput of system.展开更多
In this paper, two formation controllers are developed under directed and undirected communication topology for six-degree-of-freedom （6-DOF） networked spacecraft flying in deep space. In the control algorithm, any ...In this paper, two formation controllers are developed under directed and undirected communication topology for six-degree-of-freedom （6-DOF） networked spacecraft flying in deep space. In the control algorithm, any explicit leader does not exist in the formation team and the proposed controller is required that each spacecraft communicates with its neighbors only, which avoids having to communicate each spacecraft＇s trajectory and therefore reduces the required communication loads of the whole formation. The proposed control strategy allows that each spacecraft can track its desired position and attitude and simultaneously the whole group moves to the desired formation and obtains its desired relative attitudes between spaceerafts. Simulation results demonstrate the effectiveness of the proposed controller.展开更多
The current lunar exploration has changed from a single scientific exploration to science and resource utilization. On the basis of the previous lunar exploration, Chinese scientists and technical experts have propose...The current lunar exploration has changed from a single scientific exploration to science and resource utilization. On the basis of the previous lunar exploration, Chinese scientists and technical experts have proposed an overall plan to preliminarily build a lunar research station on the lunar South Pole by several missions before 2035, exploring of the moon, as well as the use of lunar platforms and in-site utilization of resources. In addition, China will also explore Mars, asteroids and Jupiter and its moons. This paper briefly introduces the ideas of Chinese scientists and technical experts on the lunar and deep space exploration.展开更多
文摘This paper addresses the challenges of insufficient navigation accuracy,low path-planning efficiency,and poor environmental adaptability faced by deep space rovers in complex extraterrestrial environments(e.g.,the Moon and Mars).A novel autonomous navigation scheme is proposed that integrates laser Doppler velocimetry(LDV)with star trackers(ST)and inertial navigation system(INS).The scheme suppresses slip errors from wheel odometry through non-contact,high-precision laser speed measurement(accuracy better than 0.1%).By deeply fusing multi-source data via a Kalman filter algorithm,high-precision positioning is realized under extreme extraterrestrial conditions such as weak illumination and dust coverage.This solution features high accuracy,non-contact measurement,and anti-interference capabilities,significantly improving the navigation accuracy and autonomy of deep space rovers in complex environments.
文摘With the expansion of the female player base and the increase in their purchasing power,the female-oriented game market has gradually risen.This paper employs the Uses and Gratifications Theory as a framework,using the successful case of Love and Deep Space to explore how female players satisfy their specific social and psychological needs through gaming.The study finds that female-oriented games effectively meet the diverse needs of female players in terms of content design,interactive experiences,and community building,further promoting the prosperity and development of the female-oriented game market.
文摘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.
基金supported by Program for New Century Excellent Talents in University of China (No.NCET-120030)National Natural Science Foundation of China (No.91438116)
文摘Carrier tracking is laid great emphasis and is the difficulty of signal processing in deep space communication system.For the autonomous radio receiving system in deep space, the tracking of the received signal is automatic when the signal to noise ratio（SNR） is unknown.If the frequency-locked loop（FLL） or the phase-locked loop（PLL） with fixed loop bandwidth, or Kalman filter with fixed noise variance is adopted, the accretion of estimation error and filter divergence may be caused.Therefore, the Kalman filter algorithm with adaptive capability is adopted to suppress filter divergence.Through analyzing the inadequacies of Sage–Husa adaptive filtering algorithm, this paper introduces a weighted adaptive filtering algorithm for autonomous radio.The introduced algorithm may resolve the defect of Sage–Husa adaptive filtering algorithm that the noise covariance matrix is negative definite in filtering process.In addition, the upper diagonal（UD） factorization and innovation adaptive control are used to reduce model estimation errors,suppress filter divergence and improve filtering accuracy.The simulation results indicate that compared with the Sage–Husa adaptive filtering algorithm, this algorithm has better capability to adapt to the loop, convergence performance and tracking accuracy, which contributes to the effective and accurate carrier tracking in low SNR environment, showing a better application prospect.
基金supported by the National Natural Science Fandation of China (6067208960772075)
文摘In consultative committee for space data systems（CCSDS） file delivery protocol（CFDP） recommendation of reliable transmission,there are no detail transmission procedure and delay calculation of prompted negative acknowledge and asynchronous negative acknowledge models.CFDP is designed to provide data and storage management,story and forward,custody transfer and reliable end-to-end delivery over deep space characterized by huge latency,intermittent link,asymmetric bandwidth and big bit error rate（BER）.Four reliable transmission models are analyzed and an expected file-delivery time is calculated with different trans-mission rates,numbers and sizes of packet data units,BERs and frequencies of external events,etc.By comparison of four CFDP models,the requirement of BER for typical missions in deep space is obtained and rules of choosing CFDP models under different uplink state informations are given,which provides references for protocol models selection,utilization and modification.
基金Supported by the B-type Strategic Priority Program of the Chinese Academy of Sciences(XDB41000000)the National Natural Science Foundation of China(11773081,11573073)CAS Interdisciplinary Innovation Team,Foundation of Minor Planets of the Purple Mountain Observatory and Youth Innovation Promotion Association。
文摘Four future missions for deep space exploration and future space-based exoplanet surveys on habitable planets by 2030 are scheduled to be launched.Two Mars exploration missions are designed to investigate geological structure,the material on Martian surface,and retrieve returned samples.The asteroids and main belt comet exploration is expected to explore two objects within 10 years.The small-body mission will aim to land on the asteroid and get samples return to Earth.The basic physical characteristics of the two objects will be obtained through the mission.The exploration of Jupiter system will characterize the environment of Jupiter and the four largest Moons and understand the atmosphere of Jupiter.In addition,we further introduce two space-based exoplanet survey by 2030,Miyin Program and Closeby Habitable Exoplanet Survey(CHES Mission).Miyin program aims to detect habitable exoplanets using interferometry,while CHES mission expects to discover habitable exoplanets orbiting FGK stars within 10 pc through astrometry.The above-mentioned missions are positively to achieve breakthroughs in the field of planetary science.
基金Supported by National Key R&D Program of China(2020YFE0202100)Beijing Municipal Science and Technology Commission(Z181100002918003)。
文摘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.
基金Supported by the National Natural Science Foundation of China (No. 60972061,60972062,and 61032004)the National High Technology Research and Development Program of China ("863" Program) (No. 2008AA12A204)
文摘Deep space communications has played an important role in deep space exploration. Compared with common satellite and terrestrial communications, deep space communications faces more challenging environment. The paper investigated the unique features of deep space communica-tions in detail, discussed the key technologies and its development trends for deep space communica-tions.
基金Supported by National Natural Science Foundation of China (Grant No.51775141)Heilongjiang Touyan Innovation Team Program。
文摘The spacecraft for deep space exploration missions will face extreme environments,including cryogenic temperature,intense radiation,wide-range temperature variations and even the combination of conditions mentioned above.Harsh environments will lead to solder joints degradation or even failure,resulting in damage to onboard electronics.The research activities on high reliability solder joints using in extreme environments can not only reduce the use of onboard protection devices,but effectively improve the overall reliability of spacecraft,which is of great significance to the aviation industry.In this paper,we review the reliability research on SnPb solder alloys,Sn-based lead-free solder alloys and In-based solder alloys in extreme environments,and try to provide some suggestions for the follow-up studies,which focus on solder joint reliability under extreme environments.
基金Supported by the National Natural Science Foundation of China (No. 61032003 and No. 61021001)
文摘Compared with common near space satellite Telemetry,Telecommand,and Communication(TT&C),deep space TT&C presents a more challenging environment such as long distance,very low Signal to Noise Ratio(SNR).How to acquire main carrier exactly becomes a hot focus for deep space communications.Already there emerged some main carrier acquisition algorithms,but they all require high SNR and small modulation index.In this paper,we develop a new acquire algorithm.First we use the spectral energy center algorithm to shorten the original sequence,filter out some noise and make the spectral more symmetric.Then we adopt the spectral symmetry algorithm to make full use of the whole spectrum information,and utilize FFT to reduce computation complexity.Simulation results show that our algorithm can acquire main carrier successfully under large modulation index and get good performance with low Carrier to Noise Ratio(CNR).
基金Supported by Fundamental Research Funds for the Central Universities of China(Grant No.2021JBM021)National Natural Science Foundation of China(Grant Nos.52202431,52172353).
文摘The footpad structure of a deep space exploration lander is a critical system that makes the initial contact with the ground,and thereby plays a crucial role in determining the stability and energy absorption characteristics during the impact process.The conventional footpad is typically designed with an aluminum honeycomb structure that dissipates energy through plastic deformation.Nevertheless,its effectiveness in providing cushioning and energy absorption becomes significantly compromised when the structure is crushed,rendering it unusable for reusable landers in the future.This study presents a methodology for designing and evaluating structural energy absorption systems incorporating recoverable strain constraints of shape memory alloys(SMA).The topological configuration of the energy absorbing structure is derived using an equivalent static load method(ESL),and three lightweight footpad designs featuring honeycomb-like Ni-Ti shape memory alloys structures and having variable stiffness skins are proposed.To verify the accuracy of the numerical modelling,a honeycomb-like structure subjected to compression load is modeled and then compared with experimental results.Moreover,the influence of the configurations and thickness distribution of the proposed structures on their energy absorption performance is comprehensively evaluated using finite element simulations.The results demonstrate that the proposed design approach effectively regulates the strain threshold to maintain the SMA within the constraint of maximum recoverable strain,resulting in a structural energy absorption capacity of 362 J/kg with a crushing force efficiency greater than 63%.
基金Supported by the National Natural Sciences Foundation of China (No. 61032003)
文摘Digital fountain is applied into deep space communication for its rateless and non-feedback forward error correction.However,the long code length and encoding overhead are confined factors to guarantee a considerable recovery probability as power and buffer-limited equipment in deep space environment.At the same time,the typical fountain decoding is sub-optimum decoding algorithm.We propose a new approach,Dependent Sequences Compensation Algorithm(DSCA),to improve the encoding efficiency by restricting the randomness in fountain encoding.While decoding algorithm is also optimized by redundant information in stopping set.The results show that the optimized method can obtain a 10-4 decoding failure rate with overhead under 0.20 for code length 500,which indicates the usefulness of the proposed approach in deep space communication.
文摘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.
基金supported by the National Natural Science Foundation of China(61271261)the Natural Science Foundation Project of CQ CSTC(CSTC2012jjA40048)
文摘A deep space multi-file delivery protocol（DSMDP） based on LT codes is proposed to reduce the influence of long delay and a high bit error rate（BER） in deep space communication. The protocol increases sending redundancy by LT codes to improve the success rate of file delivery, and adopts different protective strategies for different situations of packet loss. At the same time, the multi-file united delivery strategy is adopted to make full use of the retransmission time to reduce the end-toend transmission delay. Furthermore, the protocol determines the quantity of encoded packets according to the feedback for controlling redundancy. The simulation results show that the proposed protocol can significantly reduce the transmission delay of files, which would be effectively suitable for deep space communication environment of high BER and long delay.
基金supported by National Natural Science Foundation of China (61471109, 61501104 and 91438110)Fundamental Research Funds for the Central Universities ( N140405005 , N150401002 and N150404002)Open Fund of IPOC (BUPT, IPOC2015B006)
文摘With the development of science, economy and society, the needs for research and exploration of deep space have entered a rapid and stable development stage. Deep Space Optical Network(DSON) is expected to become an important foundation and inevitable development trend of future deepspace communication. In this paper, we design a deep space node model which is capable of combining the space division multiplexing with frequency division multiplexing. Furthermore, we propose the directional flooding routing algorithm(DFRA) for DSON based on our node model. This scheme selectively forwards the data packets in the routing, so that the energy consumption can be reduced effectively because only a portion of nodes will participate the flooding routing. Simulation results show that, compared with traditional flooding routing algorithm(TFRA), the DFRA can avoid the non-directional and blind transmission. Therefore, the energy consumption in message routing will be reduced and the lifespan of DSON can also be prolonged effectively. Although the complexity of routing implementation is slightly increased compared with TFRA, the energy of nodes can be saved and the transmission rate is obviously improved in DFRA. Thus the overall performance of DSON can be significantly improved.
基金supported by the Strategic Leading Project of the Chinese Academy of Sciences(No.XDA15014603).
文摘A reasonable parameter configuration helps improve the data transmission performance of the Licklider Transmission Protocol(LTP).Previous research has focused mainly on parameter optimization for LTP in simplified scenarios with one to two hops or multihop scenarios with a custody mechanism of the Bundle Protocol(BP).However,the research results are not applicable to communications in Complex Deep Space Networks(CDSNs)without the custody mechanism of BP that are more suitable for deep space communications with LTP.In this paper,we propose a model of file delivery time for LTP in CDSNs.Based on the model,we propose a Parameter Optimization Design Algorithm for LTP(LTP-PODA)of configuring reasonable parameters for LTP.The results show that the accuracy of the proposed model is at least 6.47%higher than that of the previously established models based on simple scenarios,and the proposed model is more suitable for CDSNs.Moreover,the LTP parameters are optimized by the LTP-PODA algorithm to obtain an optimization plan.Configuring the optimization plan for LTP improves the protocol transmission performance by at least 18.77%compared with configuring the other parameter configuration plans.
文摘A major limitation for deep space communication is the limited bandwidths available. The downlinkrate using X-band with an L2 halo orbit is estimated to be of only 5.35 GB/d. However, the Next GenerationSpace Telescope (NGST) will produce about 600 GB/d. Clearly the volume of data to downlink must be re-duced by at least a factor of 100. One of the resolutions is to encode the data using very low bit rate image com-pression techniques. An very low bit rate image compression method based on region of interest(ROI) has beenproposed for deep space image. The conventional image compression algorithms which encode the original datawithout any data analysis can maintain very good details and haven' t high compression rate while the modernimage compressions with semantic organization can have high compression rate even to be hundred and can' tmaintain too much details. The algorithms based on region of interest inheriting from the two previews algorithmshave good semantic features and high fidelity, and is therefore suitable for applications at a low bit rate. Theproposed method extracts the region of interest by texture analysis after wavelet transform and gains optimal localquality with bit rate control. The Result shows that our method can maintain more details in ROI than generalimage compression algorithm(SPIHT) under the condition of sacrificing the quality of other uninterested areas.
基金Sponsored by the National Natural Science Foundation of China( Grant No. 61032003)the Fundamental Research Funds for the Central Universities( Grant No. HIT. NSRIF.2012021)
文摘In this paper, according to the AR4JA codes in deep space communication, two kinds of iterative decoding including partly parallel decoding and overlapped partly parallel decoding are analyzed, and the advantages and disadvantages of them are listed. A modified overlapped partly parallel decoding that not only inherits the advantages of the two algorithms, but also overcomes the shortcomings of the two algorithms is proposed. The simulation results show that the three kinds of decoding have the same decoding performance; modified overlapped partly parallel decoding improves the iterative convergence rate and the throughput of system.
基金Supported by the National Natural Science Foundation of China （No. 10832004）.
文摘In this paper, two formation controllers are developed under directed and undirected communication topology for six-degree-of-freedom （6-DOF） networked spacecraft flying in deep space. In the control algorithm, any explicit leader does not exist in the formation team and the proposed controller is required that each spacecraft communicates with its neighbors only, which avoids having to communicate each spacecraft＇s trajectory and therefore reduces the required communication loads of the whole formation. The proposed control strategy allows that each spacecraft can track its desired position and attitude and simultaneously the whole group moves to the desired formation and obtains its desired relative attitudes between spaceerafts. Simulation results demonstrate the effectiveness of the proposed controller.
基金Supported by National Science Foundation of China(41590851)
文摘The current lunar exploration has changed from a single scientific exploration to science and resource utilization. On the basis of the previous lunar exploration, Chinese scientists and technical experts have proposed an overall plan to preliminarily build a lunar research station on the lunar South Pole by several missions before 2035, exploring of the moon, as well as the use of lunar platforms and in-site utilization of resources. In addition, China will also explore Mars, asteroids and Jupiter and its moons. This paper briefly introduces the ideas of Chinese scientists and technical experts on the lunar and deep space exploration.
