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Zhong B.,CAS Institute of Remote Sensing | Zhang Y.,CAS Institute of Remote Sensing | Du T.,Space Star Technology | Yang A.,Chongqing University of Posts and Telecommunications | And 2 more authors.
IEEE Transactions on Geoscience and Remote Sensing | Year: 2014

The charge-coupled device (CCD) is visible to near-infrared imaging sensors onboard the Chinese Huan Jing 1 satellites. Like many sensors, the CCD lack onboard calibration capabilities, so alternative methods are required, e.g., cross-calibration. The wide field of view of the CCD sensors provides challenges for cross-calibration with narrow field of view sensors. We developed a technique to take advantage of a site with a uniform surface material and a natural topographic variation. Due to the topography, near-nadir Landsat Enhanced Thematic Mapper (TM) Plus (ETM +) observations actually see the material at a wide range of illumination and viewing angles. These observations and Advanced Spaceborne Thermal Emission and Reflection Radiometer global digital elevation model data were used to develop a model of this site's bidirectional reflectance distribution function that covered most of the illumination and view angle range of the CCD data. We validated this model by comparing the simulations to actual ETM + and TM surface reflectances. The validated model was then used to calibrate the CCD instruments. The results were consistent to within 5% of field intensive vicarious calibration data. © 1980-2012 IEEE.

Yang P.,Chengdu University of Technology | Yan F.,Chengdu University of Technology | Yang F.,Chengdu University of Technology | Dong T.,Space Star Technology
IEEE Transactions on Antennas and Propagation | Year: 2016

The techniques of random antenna element distribution and rotation have been proposed to design a low sidelobe and low cross-polarization phased array or reflect array for a long time. In this communication, we demonstrate that the use of randomly rotated (RR) elements can provide random scattering phases and phase center distributions, which can lead to an in-band radar cross section (RCS) reduction for the array. To illustrate the effectiveness of the proposed method, three 8 × 8 circularly polarized (CP) microstrip arrays, 1) the uniform array without rotation; 2) sequentially rotated (SR) array; and 3) RR array, are compared and analyzed. Results indicate that the RCS of the RR array can be reduced significantly, even in the main beam region, while maintaining its high radiation performance. © 2016 IEEE.

Lu X.,Space Star Technology | Liu J.,Space Star Technology
Proceedings - 2014 9th International Conference on P2P, Parallel, Grid, Cloud and Internet Computing, 3PGCIC 2014 | Year: 2014

In this work, we consider a space network time synchronization protocol which is based on time information exchanges similar to Network Time Protocol. Further, we analyze the performance of this time protocol due to relative motion with two spacecraft through using STK and Mat lab software jointly simulation. Regard the influencing factors such as relative distance between the two spacecraft, the relative distance changes rate and time synchronization error curve relative motion of spacecraft that impact on the time synchronization accuracy. Finally, under conditions known to spacecraft orbit, this paper utilizes a error curve fitting compensating method to reduce space network time synchronization protocol synchronization in the application of the relative movement state. It is significant improvement in time synchronization errors. © 2014 IEEE.

Xiangxiang L.,Space Star Technology
ICEIEC 2015 - Proceedings of 2015 IEEE 5th International Conference on Electronics Information and Emergency Communication | Year: 2015

Based on the summarization of the demands on management services of massive remote sensing images data, the status quo at home and abroad are analyzed from the following two aspects: specification demands of data management and storage organizational structure. The advantages and defects of several typical data storage centers are compared with each other, consequently, the key technologies of the management system of massive remote sensing image data in the ground application system is discussed. © 2015 IEEE.

Liu N.,Space Star Technology
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

In this paper, we describe a flat plate array for the satellite communication receiver, with small aperture, high efficiency and low cross polarization levels. The radiating element used is circular waveguide which is probe-fed using a stripline distribution networks providing uniform excitations to the 4×4 array. The networks are placed one behind the other for dual polarized purposes. The array is composed of 2×1 subarrays. The overall array thickness is about 1λ ( λ is the wavelength of the center frequency), and the array aperture is about 3.2λ. Simulated results on a Ku-band prototype are discussed. The bandwidth (VSWR below 2.0) is about 500MHz, cross-polarized radiation from both ports is below -35dB, the isolation between the ports is below -25dB, and the gain of the 4×4 array is about 20dBi. Simulated efficiency is about 75% (including the stripline feed networks). © 2010 Copyright SPIE - The International Society for Optical Engineering.

Huang P.,Inner Mongolia University of Technology | Xu W.,CAS Institute of Electronics | Li S.,Space Star Technology
IET Radar, Sonar and Navigation | Year: 2014

This study analyses echo properties of spaceborne squinted multichannel along the track synthetic aperture radar (SAR) data. The highly squint angle and the large transmitted pulse bandwidth lead to Doppler spectrum back folding in the spaceborne squinted case. The extended Doppler bandwidth in the squinted mode increases the processing difficulty of azimuth multichannel data reconstruction. According to echo properties of the spaceborne squinted mode, a new imaging approach for spaceborne squinted multichannel SAR data focusing is proposed. The key point of this imaging approach is azimuth multichannel data preprocessing to resolve the aliased Doppler spectrum caused by both azimuth sub-sampling in each azimuth channel and the highly squint angle. Afterwards, a modified range migration algorithm is taken for consequent equivalent monostatic spaceborne squinted SAR data focusing. Simulation results on point targets and distributed target are given to validate the proposed imaging approach. © The Institution of Engineering and Technology 2014.

Huang P.,Inner Mongolia University of Technology | Li S.,Space Star Technology | Xu W.,CAS Institute of Electronics
IEEE Geoscience and Remote Sensing Letters | Year: 2014

The novel displaced phase center antenna (DPCA) azimuth multichannel technique is well suited to improve the coarser azimuth resolution of the terrain observation by progressive scans (TOPS) mode for a fixed total receive antenna length. However, both the azimuth multichannel nonuniform sampling and the aliased Doppler spectrum in TOPS raise the azimuth data processing difficulty. This letter proposes an innovative full-aperture processing approach, which adds an azimuth derotation step for each azimuth channel before azimuth multichannel data reconstruction and utilizes the prefiltering operation in the two-step focusing technique to resolve both azimuth ambiguity problems caused by the DPCA technique and azimuth beam progressive scanning. In addition to presenting the proposed azimuth preprocessing approach, the impact of the approach on the azimuth ambiguity-to-signal ratio is analyzed in detail. Simulation results validate the proposed multichannel processing approach for the TOPS mode. © 2013 IEEE.

Wang Y.,Space Star Technology
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

A novel antenna is proposed in this article, which has simple structure, high gain, wide-band, omni direction and small physical size characteristics. Through optimized design, the maximum gain in omnidirectional plane is 5.0dB, the 3dB beam width in the normal plane ≥40°, the absolute VSWR band width of this antenna is 22.2GHz, and the relative VSWR band width is about 73% (VSWR<2), so the antenna can cover the K/Ka band. Because of the merits of the high gain and wide band, this antenna is not just used in the satellite communication, but also in the other domain such as the mobile communication. © 2010 Copyright SPIE - The International Society for Optical Engineering.

Zhou J.,Beijing Institute of Technology | Dong T.,Space Star Technology
Eurasip Journal on Wireless Communications and Networking | Year: 2015

According to the loss network problems caused by limited resources and environment interference factors, we presented a survivability mechanism based on mobility prediction and based on the topological evolution of cloud computing wireless multimedia sensor network (WMSN). First, based on cooperative neural network and opportunity Markov chain model, the multimedia mobile sensor node state and state transition probability could be predicted. Then, the opportunity computational scheme was given based on mobility prediction of dynamic topology evolution mechanism. Finally, using the network topology reconfiguration and opportunities for cloud computing, an enhanced WMSN survivability and end-to-end quality of service guarantee mechanism was proposed. Experimental results show that compared with the static scheme for WMSNs, the proposed survivability mechanism has the obvious advantage in the node protection, data communication, network life cycle, and decodable frame rate and other aspects, and can effectively improve the invulnerability of WMSNs. © 2015, Zhou and Dong.

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