基于LEON2和FPGA的在轨图像小波变换模块设计

利用Leon2处理器核和具有丰富内部资源的FPGA芯片,为空间太阳望远镜（SST）图像压缩单元成功设计了高性能的基于纯硬件架构的（5,3）整数一整数二维小波变换模块。该模块对2048×1024×2B的太阳图像进行变换耗时约为0．2S,比欧空局（ESA）的DSP软件方法提高了数十倍运算速度,不仅满足SST卫星在轨图像压缩的任务指标,而且在结构上也易于与其后的多种编码处理灵活衔接,同时还具有体积小、功耗低、容错性好、通用性强等特点,可以广泛应用于多种航天图像压缩领域。     

面向星载交换的地面检测系统设计与实现

卫星互联网作为国家新型基础设施建设的重要组成部分，在国家战略、技术发展以及产业需求的多重驱动下，发展迅速。星载交换技术决定着空间网络的容量和组网能力，是实现全域覆盖卫星互联网的关键。针对大容量星载交换设备在轨维修难度大且价格昂贵的问题，设计了面向多接口、大容量星载交换设备的地面检测系统；基于现场可编程门阵列(Field Programmable Gate Array, FPGA)完成了地面检测系统的软硬件开发，实现了地面检测系统的测试和大容量星载交换设备的在地功能测试，保障了星载设备在轨的正常运行。     

Hα太阳空间望远镜热设计

Hα太阳空间望远镜具有对日光谱成像及全日面成像功能,具有多功能、高度集成化的特点。它位于卫星载荷舱内,在轨姿态多变,并且具有连续观测的工作模式,焦平面组件及电单机工作热环境苛刻,对热设计提出较高要求。通过星载一体化设计及相机结构合理布局,在卫星舱板靠近相机处预留辐射散热通道,合理设计散热面将工作热耗快速导出,保证各部组件温度满足指标要求。搭建热平衡试验平台,对高低温工况下的热分析和热平衡试验及在轨数据进行对比,同一工况下各电单机最大温差≤4℃,对热设计的正确性进行了验证。保证了Hα太阳空间望远镜在复杂空间环境下的正常工作,对此类空间太阳望远镜热控设计具有一定的借鉴意义。     

空间太阳望远镜图像积分中1 bit相关器的研究

空间太阳望远镜(SST)系统采用图像积分方法提高太阳矢量磁图的信噪比(SNR).在图像积分过程中,基于图像强度信息的相关器难以满足航天应用中系统实时性和低资源消耗要求,为此提出使用1 bit相关器实现图像快速相关运算.1 bit相关算法以异或逻辑运算代替常规算法中的乘法,提高了运算速度,同时减小硬件实现复杂度.针对太阳米粒图像,给出1 bit相关算法方案,并研制出基于FPGA DSP架构的相关器.测试结果表明,该相关器的算法精度、相关运算时间均能满足SST需求,而FPGA资源消耗仅为基于快速傅里叶变换(FFT)相关器(8 bit数据)的1/10.     

基于FPGA的星载图像压缩系统

为了解决星地间的数据通信,阐述了基于FPGA平台的JPEG图像压缩系统的设计与实现。为提高数据吞吐量和降低结构复杂性,对JPEG标准算法进行了优化,减少了硬件资源开销,采用改进的快速DCT运算,量化由乘法替代除法操作,扫描用查找表以避免使用RAM资源,由熵编码经转换输出预定义的压缩码流。实验结果表明,该系统功耗低、可靠性高,满足星载图像压缩系统的预期指标要求。     

星载环境FPGA软件在轨重加载的一种方法

FPGA在空间系统中已经广泛应用,为了满足系统可靠性和可扩展性的要求,实现FPGA软件的在轨重加载迫在眉睫。根据FPGA的加载配置原理,以Xilinx公司的Virtex-Ⅱ系列FPGA为实例,介绍了FPGA在轨重加载的硬件电路设计以及软件设计。经过实验室测试验证,该设计方法合理可行,满足星载环境下FPGA软件在轨编程及重加载的设计需求。     

空间太阳望远镜主光学望远镜热效应分析

空间太阳望远镜(SST)直接对日成像,其1m口径的主反射镜(MOT)接收到的上千瓦热量将严重影响望远镜的成像质量,因此必须进行热控设计以确保SST的性能.首先讨论了SST主镜筒内的热状况,分析了对日观测时主镜筒内的热流分布情况;然后根据SST轨道参数计算望远镜的空间轨道外热流状况;在此基础上提出了相应的热控措施,并使用...     

星载大气痕量气体差分吸收光谱仪定标机构设计

星载大气痕量气体差分吸收光谱仪(星载仪器)搭载于太阳同步轨道卫星上,应用于定量监测全球空气质量变化以及污染气体的分布输运过程。星上定标是成像光谱仪获取数据定量化应用的基础,星载仪器采用太阳光定标方式和标准灯定标方式进行在轨定标。需对星上定标方式采用的定标机构进行分析和合理的设计,以保证星载仪器在轨定标的可靠性和精度。     

一种基于DSP的视频图像压缩系统的设计

介绍了一种基于DSP技术的视频图像压缩系统的实现方法,以TI公司的TMS320VC5402DSP为处理器设计低成本视频图像压缩板.该压缩板是一个独立的视频图像压缩和传输设备,它能直接对全彩色电视信号进行数字化和压缩编码.利用DSP对单幅画面采用JPEG压缩方法,然后以尽快连续方式将各单幅画面联系起来,并通过USB总线将图像数据发送到微机.     

基于ADV212的光谱数据压缩系统研究

为了解决现有的存储介质和传输带宽与成像光谱仪(imaging spectrometer)异常庞大的光谱数据量之间的矛盾,本论文选用FPGA搭载JPEG2000压缩专用图像压缩芯片ADV212的方式;利用Xilinx的嵌入式开发套件所提供的可编程嵌入式开发平台和Xilinx MicroBlaze软核处理器设计了硬件系统来实现光谱数据压缩。系统设计使用专用图像压缩芯片,所以不必花费大量时间对JPEG2000算法进行优化,处理数据的速度较高,还原图像的质量较好而且实现起来简单,技术成熟可靠稳定。并在基于DMD的哈达玛成像光谱仪上对所设计系统进行了验证。结果表明该系统达到实时压缩光谱数据的要求。     

西北太平洋海表温度的季节变化特征

通过分析新的SODA资料,得到西北太平洋上层海表温度时空分布特征,剖析了西北太平洋海表温度的季节变化及经纬向分布特征,得出西北太平洋声速值变化规律。资料分析表明：西北太平洋海表温度存在着显著的季节变化特征。在季节变化中,春季由于太阳辐射加强,使整个海域海表温度比冬季约高2℃,整个西北太平洋东南部SST等温线分布较为平缓;夏季SST受太阳辐射的影响而整体升高,分布均匀且南北温差较小;秋季海表温度开始降低;冬季海表温度整体降低,等温线达到全年最低,南北温差较大。海表温度基本上是纬向分布,低纬海洋温度在20～30℃之间,高纬海洋降至0～1℃,等温线在中纬度（40°N附近）最密集,南北温度梯度最大。     

Hierarchical oriented predictions for resolution scalable lossless and near-lossless compression of CT and MRI biomedical images

We propose a new hierarchical approach to resolution scalable lossless and near-lossless (NLS) compression. It combines the adaptability of DPCM schemes with new hierarchical oriented predictors to provide resolution scalability with better compression performances than the usual hierarchical interpolation predictor or the wavelet transform. Because the proposed hierarchical oriented prediction (HOP) is not really efficient on smooth images, we also introduce new predictors, which are dynamically optimized using a least-square criterion. Lossless compression results, which are obtained on a large-scale medical image database, are more than 4% better on CTs and 9% better on MRIs than resolution scalable JPEG-2000 (J2K) and close to nonscalable CALIC. The HOP algorithm is also well suited for NLS compression, providing an interesting rate-distortion tradeoff compared with JPEG-LS and equivalent or a better PSNR than J2K for a high bit rate on noisy (native) medical images.     

Partial encryption of compressed images and videos

The increased popularity of multimedia applications places a great demand on efficient data storage and transmission techniques. Network communication, especially over a wireless network, can easily be intercepted and must be protected from eavesdroppers. Unfortunately, encryption and decryption are slow, and it is often difficult, if not impossible, to carry out real-time secure image and video communication and processing. Methods have been proposed to combine compression and encryption together to reduce the overall processing time, but they are either insecure or too computationally intensive. We propose a novel solution called partial encryption, in which a secure encryption algorithm is used to encrypt only part of the compressed data. Partial encryption is applied to several image and video compression algorithms in this paper. Only 13-27% of the output from quadtree compression algorithms is encrypted for typical images, and less than 2% is encrypted for 512×512 images compressed by the set partitioning in hierarchical trees (SPIHT) algorithm. The results are similar for video compression, resulting in a significant reduction in encryption and decryption time. The proposed partial encryption schemes are fast, secure, and do not reduce the compression performance of the underlying compression algorithm     

空间太阳望远镜主光学望远镜叶片结构热效应

空间太阳望远镜（Space Solar Telescope,SST）主光学望远镜（Main Optical Telescope,MOT）口径达1 m,以2.8'1.5'视场对太阳成像,将获得0.1～0.15的高空间分辨率和高信噪比图像。SST MOT对日局部视场观测时系统所接收到的超千瓦热量,成为对望远镜成像产生极强影响的热源和杂散光源。基于SST MOT的特殊工况与需求,提出了MOT主镜筒在消杂光设计过程中需要兼容考虑叶片结构的热效应,讨论了同时影响该结构的几何结构特征函数（Geometry Composing Function,GCF）与辐射角系数的关联因素,确定了叶片结构热控与消杂光兼容设计的目标与评价体系。借助热分析软件计算了SST MOT主镜筒内因叶片结构不同几何参数变化后引起的系统温度的变化趋势,从热控角度对叶片结构的几何设计提出了建议:叶片优先采用垂直型结构、有效高度尽可能小,且叶片与主镜轴向间距应大于425 mm。文中探索的叶片结构热效应与杂散光效应兼容分析的方法也可为其他太阳光学望远镜的综合优化设计提供参考。     

一种有效的合成孔径雷达原始数据高倍数压缩算法

在分析分块自适应量化(BAQ)压缩数据的分布特性、量化信噪比、动态范围及其对矢量量化数据压缩性能和运算量影响的基础上,对分块自适应矢量量化(BAVQ)压缩算法进行了改进,提出了采用高比特数BAQ压缩的方案.利用改进的BAVQ算法压缩高分辨率SAR原始数据的结果表明,在相同压缩比的条件下,该文提出的改进算法可获得更大的量化信噪比.解压缩数据生成的图像可以清晰地保留图像中的细节信息.     

Computing advective velocities from satellite images of sea surfacetemperature

A method of employing sequential satellite images of sea surface temperature (SST) patterns to estimate surface advective current velocities is described. SST images are obtained by processing data received twice daily from the Advanced Very High Resolution Radiometer. The current velocities are estimated by applying a maximum cross correlation (MCC) technique on two time-lapsed images. The MCC technique involves computing matrices of cross correlation coefficients and identifying correlation peaks. A two-stage multilevel statistical test over two-dimensional correlations is developed for determining the relative significance levels of velocity estimates. The test also identifies areas where the MCC technique cannot be effective. Aspects of implementation and limitations of the MCC technique for computing current velocity are also discussed. Advective velocity fields computed through MCC for the Chatham Rise area in New Zealand extending from (40.5°S, 173.5°E) to (49°S, 178°W) show good agreement with the known geostrophic flow patterns in this area     

Data compression on the illumination adjustable images by PCA and ICA

In the image-based relighting (IBL), tremendous reference images are needed to provide a high quality rendering. Therefore, a data compression is a must for its real applications. In this paper, two global analysis methods, the principal component analysis (PCA) and the independent component analysis (ICA), are used to compress the huge IBL data by exploiting its correlation properties. Both approaches approximate the raw data with a small number of global base images, and they follow a similar algorithm structure: base images extraction, raw data representation, and further compression on the base images and the representing coefficients. What differs is that PCA only removes the second-order data correlation, but ICA reduces nearly all order statistics data dependence, which should benefit the data compression. Simulations are given to evaluate their performance. Comparisons are also made between them and JPEG2000 and MPEG. The evaluation results show that both approaches are superior to JPEG2000 and MPEG. Although ICA tends to remove higher order dependence than PCA, it is a little inferior to PCA in terms of compression ratio/reconstruction error performance.     

空间太阳望远镜主光学望远镜内遮光罩热效应

空间太阳望远镜（Space Solar Telescope，SST）主光学望远镜（Main Optical Telescope，MOT）口径达1 m，以2.81.5有效视场对日成像，将获得0.1～0.15的图像。SST MOT对日观测时所接收到的热量超过千瓦，成为影响望远镜成像质量的主要热源和杂散光源。为此，文中首先探讨了大口径太阳望远镜热设计与消杂光设计的特殊关联。然后，针对主镜筒内消杂散光的内遮光罩结构提出了热兼容设计，确定了内遮光罩结构热-杂散光效应集成设计的目标与评价体系。借助热分析软件获取SST MOT因内遮光罩结构参数变化引起的系统温度的变化趋势，从热控角度对内遮光罩结构的设计提出了建议:内遮光罩结构的垂直高度不宜超过400 mm。探索的内遮光罩结构热-杂散光效应集成分析方法也可为其他太阳望远镜的综合优化提供参考。     

Rate allocation for spotlight SAR phase history data compression

Complex phase history data in synthetic aperture radar (SAR) systems require extensive processing before useful images can be obtained. In spotlight mode SAR systems, useful images can be obtained by applying aperture weighting and inverse Fourier transform operations to SAR phase history data. In this paper, we are concerned with the compression of the complex phase history data obtained by a spotlight SAR system. We exploit knowledge of the aperture weighting function along with Fourier transform processing to attach a "gain" factor to each complex phase history data sample. This gain factor is then used to efficiently allocate bits to the phase history data during quantization. Performance evaluations are presented for this compression system relative to other existing SAR phase history data compression systems.