HY-1 CCD宽波段水色要素反演算法

利用2003年春季黄海、东海区现场实测数据,建立了HY1卫星4波段CCD成像仪水色要素反演算法.由于HY1CCD的宽波段特性阻碍了黄色物质的反演,因此反演的水色要素仅包括水体表层的总悬浮物、悬浮泥沙(SS)以及叶绿素a的浓度.现场遥感反射率光谱由ASD地物波谱仪测量,对于叶绿素a的浓度利用现场萃取荧光法测量,总悬浮物、悬浮泥沙由实验室滤膜称重法获得.反演算法的拟合相关系数均大于0.88,平均相对误差在40%以下.对反演算法进行了误差灵敏度分析,结果表明对于总悬浮物、悬浮泥沙和低浊度水体中的叶绿素a的浓度反演算法能够满足日常的业务运行要求,但是对于高浊度水体中叶绿素a的浓度反演算法对某个波段组合比较敏感,仍需要进一步探讨.     

两种典型三维CT系统及应用

三维CT系统是CT研究最活跃的前沿课题之一,三维重建算法1984年就由Feldcamp等提出,完成了三维CT的数学基础,为把计算时间减少到可接受的程度,我们采用几何参数表法成倍地缩短了重建时间.随着面阵列CCD探测器和新型平板探测器的出现,三维CT的硬件基础也已成熟,本文介绍了基于科研级CCD相机和非晶硅平板探测器的两种典型三维CT系统,并介绍了应用以上两套三维CT在生物医学和工业无损检测中的部分应用结果.     

CCD˫�������ǵ����Ƽ�Ӧ��

?????????????????????????????????????????????????????????????????λ??????????С????н?????????????????????????????Ч?????á?     

Assessment of total suspended sediment concentrations in Poyang Lake using HJ-1A/1B CCD imagery

We explored the potential of the environment and disaster monitoring and forecasting small satellite constellations (HJ-1A/1B satellites) charge-coupled device (CCD) imagery (spatial resolution of 30 m, revisit time of 2 days) in the monitoring of total suspended sediment (TSS) concentrations in dynamic water bodies using Poyang Lake, the largest freshwater lake in China, as an example. Field surveys conducted during October 17-26, 2009 showed a wide range of TSS concentration (3-524 mg/L). Atmospheric correction was implemented using the Fast Line-of-sight Atmospheric Analysis of Spectral Hypercubes (FLAASH) module in ENVI with the aid of aerosol information retrieved from concurrent Terra/Moderate Resolution Imaging Spectroradiometer (MODIS) surveys, which worked well at the CCD bands with relatively high reflectance. A practical exponential retrieval algorithm was created between satellite remote sensing reflectance and in-situ measured TSS concentration. The retrieved results for the whole water area matched the in-situ data well at most stations. The retrieval errors may be related to the problem of scale matching and mixed pixel. In three selected subregions of Poyang Lake, the distribution trend of retrieved TSS was consistent with that of the field investigation. It was shown that HJ-1A/1B CCD imagery can be used to estimate TSS concentrations in Poyang Lake over synoptic scales after applying an appropriate atmospheric correction method and retrieval algorithm.     

Results of Optical Monitoring of Cataclysmic Variable GK Per in 2004

The preliminary results of ground-based UBV photometric and CCD observations of cataclysmic variable GK Per during the outburst in autumn of 2004 are presented.     

Gain calibration of CCD systems at VBO

The system gain of two CCD systems in regular use at the Vainu Bappu Observatory, Kavalur, is determined at a few gain settings. The procedure used for the determination of system gain and base-level noise is described in detail. The Photometrics CCD system at the 1-m reflector uses a Thomson-CSF TH 7882 CDA chip coated for increased ultraviolet sensitivity. The gain is programme-selected through the parameter ‘cgain’ varying between 0 and 4095 in steps of 1. The inverse system gain for this system varies almost linearly from 27.7 electrons DN^-1 at cgain = 0 to 1.5 electrons DN^-1 at cgain = 500. The readout noise is ≲ 11 electrons at cgain = 66. The Astromed CCD system at 2.3-m Vainu Bappu Telescope uses a GEC P8603 chip which is also coated for enhanced ultraviolet sensitivity. The amplifier gain is selected in discrete steps using switches in the controller. The inverse system gain is 4.15 electrons DN^-1 at the gain setting of 9.2, and the readout noise ∼ 8 electrons.     

CCD图像暗场拍摄与处理

重点讨论了天文ＣＣＤ器件暗场图像的拍摄与处理。从多幅暗场图的拍摄发现，除了某些象素的暗流值，有随积分时间成正比例的变化之外；另有一些象素，可能有随机性很大的偶发的高暗流值。其原因无论是器件内部的，还是外部的，都不应视作为“暗场”记录。拍摄多幅图，用“中值法”处理，可以得到我们需要的“暗场”     

视频CCD观测的星径曲率改正

视频ＣＣＤ观测与低纬子午环原来设计的光子计数狭缝测微器观测有不同之处。在观测数据的归算过程中，应加以考虑的星径曲率改正包括三种改正量；卯酉方向记录时刻的星径曲率改正；卯酉方向天顶距的星径曲率改正以及子午方向天顶距的星径曲率改正。     

CCD图像的二维修正矩定心方法

对于天体测量而言，ＣＣＤ图像的数字星像处理方法是十分重要的．本文根据ＣＣＤ器件的特性，从理论上推导了二维修正矩算法的最佳门限取值方法．通过处理模拟和实测数据，与传统的二维高斯拟合法比较，在保持矩方法简便特性的同时，在精度上亦有所提高，对于暗星效果更为明显．