More than 3 million range measurements from the Chang’E-1 Laser Altimeter have been used to produce a global topographic model of the Moon with improved accuracy. Our topographic model, a 360th degree and order spher...More than 3 million range measurements from the Chang’E-1 Laser Altimeter have been used to produce a global topographic model of the Moon with improved accuracy. Our topographic model, a 360th degree and order spherical harmonic expansion of the lunar radii, is designated as Chang’E-1 Lunar Topography Model s01 (CLTM-s01). This topographic field, referenced to a mean radius of 1738 km, has an absolute vertical accuracy of approximately 31 m and a spatial resolution of 0.25° (～7.5 km). This new lunar topographic model has greatly improved previous models in spatial coverage, accuracy and spatial resolution, and also shows the polar regions with the altimeter results for the first time. From CLTM-s01, the mean, equatorial, and polar radii of the Moon are 1737103, 1737646, and 1735843 m, respectively. In the lunar-fixed coordinate system, this model shows a COM/COF offset to be (?1.777, ?0.730, 0.237) km along the x, y, and z directions, respectively. All the basic lunar shape parameters derived from CLTM-s01 are in agreement with the results of Clementine GLTM2, but CLTM-s01 offers higher accuracy and reliability due to its better global samplings.展开更多
Previous analyses showed a clear asymmetry in the topography,geological material distribution,and crustal thickness between the nearside and farside of the Moon. Lunar detecting data,such as topography and gravity,hav...Previous analyses showed a clear asymmetry in the topography,geological material distribution,and crustal thickness between the nearside and farside of the Moon. Lunar detecting data,such as topography and gravity,have made it possible to interpret this hemisphere dichotomy. The high-resolution lunar topographic model CLTM-s01 has revealed that there still exist four unknown features,namely,quasi-impact basin Sternfeld-Lewis (20°S,232°E),confirmed impact basin Fitzgerald-Jackson (25°N,191°E),crater Wugang (13°N,189°E) and volcanic deposited highland Yutu (14°N,308°E). Furthermore,we analyzed and identified about eleven large-scale impact basins that have been proposed since 1994,and classified them according to their circular characteristics.展开更多
In the day time of the Moon surface, the strong illumination from high altitude and high albedo rate radical craters will introduce the illumination effect on observing the nearby low altitude, low albedo rate and sha...In the day time of the Moon surface, the strong illumination from high altitude and high albedo rate radical craters will introduce the illumination effect on observing the nearby low altitude, low albedo rate and shallow small slop rate area seriously, and even can 'hide' the later area from the light. Based on the lunar global topography model obtained by Chang’E-1 mission, and by comparing with the lunar gravity model, a volcano named 'YUTU Mountain' has been identified. It is a volcano with diameter of ~300 km and height of ~2 km located at (14°N, 308°E) in Oceanus Procellarum. Besides, the DEM of another volcano named 'GUISHU Mountain' in the same area has been improved. This new discovery will benefit the study of lunar magmatism and volcanism evolution in the nearside of the Moon.展开更多
A prototype based on digital radio technology with associated open-loop Doppler signal processing techniques has been developed to measure a spacecraft's line-of-sight velocity. The prototype was tested in China&#...A prototype based on digital radio technology with associated open-loop Doppler signal processing techniques has been developed to measure a spacecraft's line-of-sight velocity. The prototype was tested in China's Chang'E-1 lunar mission relying on S-band telemetry signals transmitted by the sat-ellite,with results showing that the residuals had a RMS value of ～3 mm/s (1σ ) using 1-sec integration,which is consistent with the Chinese conventional USB (Unified S-Band) tracking system. Such preci-sion is mainly limited by the short-term stability of the atomic (e.g. rubidium) clock at the uplink ground station. It can also be improved with proper calibration to remove some effects of the transmission media (such as solar plasma,troposphere and ionosphere),and a longer integration time (e.g. down to 0.56 mm/s at 34 seconds) allowed by the spacecraft dynamics. The tracking accuracy can also be in-creased with differential methods that may effectively remove most of the long-term drifts and some of the short-term uncertainties of the uplink atomic clock,thereby further reducing the residuals to the 1 mm/s level. Our experimental tracking data have been used in orbit determination for Chang'E-1,while other applications (such as the upcoming YH-1 Mars orbiter) based on open-loop Doppler tracking will be initiated in the future. Successful application of the prototype to the Chang'E-1 mission in 2008 is believed to have great significance for China's future deep space exploration.展开更多
Sliding polynomial modeling has undergone considerable development and has been widely applied to dynamic modeling. One focus of the polynomial model is to make efficient use of prior information, which can also be ca...Sliding polynomial modeling has undergone considerable development and has been widely applied to dynamic modeling. One focus of the polynomial model is to make efficient use of prior information, which can also be called additional or constrained information. Considering the fact that much additional information can be translated to equality constraints, we develop a new two-stage approach for sliding polynomial modeling with equality constraints. To maintain its compatibility with the polyno-mial model without this constraint, only a simple adjustment based on the constraint equation is involved in the algorithm. The approach is easy to implement and is superior in observability, convergence and accuracy. The results of a simulation study of spacecraft tracking are provided to confirm the theoretical development. As no special hypotheses are required, the approach presented here can be widely applied to dynamic modeling for nonlinear systems with equality constraints. Furthermore, per-formance predictions for other dynamic models can also draw lessons from this approach.展开更多
In the paper,a set of algorithms to construct synthetic aperture radar（SAR）matching suitable features are frstly proposed based on the evolutionary synthesis strategy.During the process,on the one hand,the indexes o...In the paper,a set of algorithms to construct synthetic aperture radar（SAR）matching suitable features are frstly proposed based on the evolutionary synthesis strategy.During the process,on the one hand,the indexes of primary matching suitable features（PMSFs）are designed based on the characteristics of image texture,SAR imaging and SAR matching algorithm,which is a process involving expertise;on the other hand,by designing a synthesized operation expression tree based on PMSFs,a much more flexible expression form of synthesized features is built,which greatly expands the construction space.Then,the genetic algorithm-based optimized searching process is employed to search the synthesized matching suitable feature（SMSF）with the highest effciency,largely improving the optimized searching effciency.In addition,the experimental results of the airborne synthetic aperture radar ortho-images of C-band and P-band show that the SMSFs gained via the algorithms can reflect the matching suitability of SAR images accurately and the matching probabilities of selected matching suitable areas of ortho-images could reach 99±0.5%.展开更多
基金Supported by the National Natural Science Foundation of China (Grant Nos 2008AA12A209 and 2008AA12A210)supported by Chang'E-1 monitoring and control systems, scientific applications system and the satellite systemssupported by the knowledge innovation project the "Hun-dred Excellent Project" of Chinese Academy of Sciences
文摘More than 3 million range measurements from the Chang’E-1 Laser Altimeter have been used to produce a global topographic model of the Moon with improved accuracy. Our topographic model, a 360th degree and order spherical harmonic expansion of the lunar radii, is designated as Chang’E-1 Lunar Topography Model s01 (CLTM-s01). This topographic field, referenced to a mean radius of 1738 km, has an absolute vertical accuracy of approximately 31 m and a spatial resolution of 0.25° (～7.5 km). This new lunar topographic model has greatly improved previous models in spatial coverage, accuracy and spatial resolution, and also shows the polar regions with the altimeter results for the first time. From CLTM-s01, the mean, equatorial, and polar radii of the Moon are 1737103, 1737646, and 1735843 m, respectively. In the lunar-fixed coordinate system, this model shows a COM/COF offset to be (?1.777, ?0.730, 0.237) km along the x, y, and z directions, respectively. All the basic lunar shape parameters derived from CLTM-s01 are in agreement with the results of Clementine GLTM2, but CLTM-s01 offers higher accuracy and reliability due to its better global samplings.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 10973031, 2008AA12A209 and 2008AA12A210)the CAS Key Research Program (Grant No. KJCX2-YW-T13-2) Recommended by ZHAO Ming
文摘Previous analyses showed a clear asymmetry in the topography,geological material distribution,and crustal thickness between the nearside and farside of the Moon. Lunar detecting data,such as topography and gravity,have made it possible to interpret this hemisphere dichotomy. The high-resolution lunar topographic model CLTM-s01 has revealed that there still exist four unknown features,namely,quasi-impact basin Sternfeld-Lewis (20°S,232°E),confirmed impact basin Fitzgerald-Jackson (25°N,191°E),crater Wugang (13°N,189°E) and volcanic deposited highland Yutu (14°N,308°E). Furthermore,we analyzed and identified about eleven large-scale impact basins that have been proposed since 1994,and classified them according to their circular characteristics.
基金Supported by the "Hundred Talent" Project of Chinese Academy of Sciences, Navi-gation Key Laboratory of Shanghai, Key Laboratory of Flying Dynamics of BACC, National Natural Science Foundation of China (Grant No. 10973031)National High-Tech Research and Development Program of China (Grant Nos. 2008AA12A209, 2008AA12A210)
文摘In the day time of the Moon surface, the strong illumination from high altitude and high albedo rate radical craters will introduce the illumination effect on observing the nearby low altitude, low albedo rate and shallow small slop rate area seriously, and even can 'hide' the later area from the light. Based on the lunar global topography model obtained by Chang’E-1 mission, and by comparing with the lunar gravity model, a volcano named 'YUTU Mountain' has been identified. It is a volcano with diameter of ~300 km and height of ~2 km located at (14°N, 308°E) in Oceanus Procellarum. Besides, the DEM of another volcano named 'GUISHU Mountain' in the same area has been improved. This new discovery will benefit the study of lunar magmatism and volcanism evolution in the nearside of the Moon.
基金Supported by the Innovation Research Plan of CAS,the National Natural Science Foundation of China (Grant Nos. 10973031 and 40904006)the CAS Key Research Program (Grant No. KJCX2-YW-T13-2), and Beijing Aerospace Command and Control Center
文摘A prototype based on digital radio technology with associated open-loop Doppler signal processing techniques has been developed to measure a spacecraft's line-of-sight velocity. The prototype was tested in China's Chang'E-1 lunar mission relying on S-band telemetry signals transmitted by the sat-ellite,with results showing that the residuals had a RMS value of ～3 mm/s (1σ ) using 1-sec integration,which is consistent with the Chinese conventional USB (Unified S-Band) tracking system. Such preci-sion is mainly limited by the short-term stability of the atomic (e.g. rubidium) clock at the uplink ground station. It can also be improved with proper calibration to remove some effects of the transmission media (such as solar plasma,troposphere and ionosphere),and a longer integration time (e.g. down to 0.56 mm/s at 34 seconds) allowed by the spacecraft dynamics. The tracking accuracy can also be in-creased with differential methods that may effectively remove most of the long-term drifts and some of the short-term uncertainties of the uplink atomic clock,thereby further reducing the residuals to the 1 mm/s level. Our experimental tracking data have been used in orbit determination for Chang'E-1,while other applications (such as the upcoming YH-1 Mars orbiter) based on open-loop Doppler tracking will be initiated in the future. Successful application of the prototype to the Chang'E-1 mission in 2008 is believed to have great significance for China's future deep space exploration.
基金supported by the National Natural Science Foundation of China(Grant Nos.61072115and60901071)
文摘Sliding polynomial modeling has undergone considerable development and has been widely applied to dynamic modeling. One focus of the polynomial model is to make efficient use of prior information, which can also be called additional or constrained information. Considering the fact that much additional information can be translated to equality constraints, we develop a new two-stage approach for sliding polynomial modeling with equality constraints. To maintain its compatibility with the polyno-mial model without this constraint, only a simple adjustment based on the constraint equation is involved in the algorithm. The approach is easy to implement and is superior in observability, convergence and accuracy. The results of a simulation study of spacecraft tracking are provided to confirm the theoretical development. As no special hypotheses are required, the approach presented here can be widely applied to dynamic modeling for nonlinear systems with equality constraints. Furthermore, per-formance predictions for other dynamic models can also draw lessons from this approach.
基金supported by National Natural Science Foundation of China (Grant No.41204026)Advanced Research Foundation (Grant No.9140A24060712KG13290)Open Fund of Key Laboratory of Science and Technology on Aerospace Flight Dynamics (Grant No.2012AFDL010)
文摘In the paper,a set of algorithms to construct synthetic aperture radar（SAR）matching suitable features are frstly proposed based on the evolutionary synthesis strategy.During the process,on the one hand,the indexes of primary matching suitable features（PMSFs）are designed based on the characteristics of image texture,SAR imaging and SAR matching algorithm,which is a process involving expertise;on the other hand,by designing a synthesized operation expression tree based on PMSFs,a much more flexible expression form of synthesized features is built,which greatly expands the construction space.Then,the genetic algorithm-based optimized searching process is employed to search the synthesized matching suitable feature（SMSF）with the highest effciency,largely improving the optimized searching effciency.In addition,the experimental results of the airborne synthetic aperture radar ortho-images of C-band and P-band show that the SMSFs gained via the algorithms can reflect the matching suitability of SAR images accurately and the matching probabilities of selected matching suitable areas of ortho-images could reach 99±0.5%.
