Polar Visible Imaging System (VIS) Earth Camera Images, Calibrated (E0), 4 min Data

Instrument Functional Description: The VIS Instrument is a Set of three Low Light Level Cameras. Two of these Cameras share primary and some secondary Optics and are designed to provide Images of the Nighttime Auroral Oval at Visible Wavelengths. A Third Camera is used to monitor the Directions of the Fields-of-View of the Auroral Cameras with respect to the sunlit Earth and return Global Images of the Auroral Oval at Ultraviolet Wavelengths. The VIS Instrumentation produces an Auroral Image of 256 × 256 Pixels approximately every 24 s dependent on the Integration Time and Filter selected. The Fields-of-View of the two Nighttime Auroral Cameras are 5.6 × 6.3° and 2.8 × 3.3° for the Low and Medium Resolution Cameras, respectively. The Medium Resolution Camera was never activated. One or more Earth Camera Images of 256 × 256 Pixels are produced every 5 min, depending on the commanded Mode. The Field-of-View of the Earth Camera is approximately 20 × 20°. See: http://vis.physics.uiowa.edu/vis/vis_description/vis_description.htmlx Reference: Frank, L.A., J.B. Sigwarth, J.D. Craven, J.P. Cravens, J.S. Dolan, M.R. Dvorsky, J.D. Harvey, P.K. Hardebeck, and D. Muller, The Visible Imaging System (VIS) for the Polar Spacecraft, Space Science Review, Vol. 71, pp. 297-328, 1995. Data Set Description: The VIS Earth Camera Data Set comprises all Earth Camera Images for the selected Time Period. Full Coordinate Information is included for Viewer Orientation. In addition, a Rotation Matrix and a Table of Distortion-correcting Look Direction Unit Vectors are provided for the Purpose of calculating Coordinates for every Pixel. To facilitate viewing of the Images, a Mapping of Pixel Value to a recommended Color Table based on the Characteristics of the selected Filter will be included with each Image. A Relative Intensity Scale is provided through an Uncompressed Count Table. Approximate Intensity Levels in kiloRayleighs are given in an Intensity Table. For detailed Information on Intensities, see Sensitivities_and_Intensities.txt at https://cdaweb.gsfc.nasa.gov/Polar_VIS_docs/SENSITIVITIES_AND_INTENSITIES.TXT. Supporting Software is available at: http://vis.physics.uiowa.edu/vis/software/ Included is an IDL Program that displays the Images with the recommended Color Bar, provides approximate Intensities, Coordinate Data for each Pixel, and includes multiple Options for Image Manipulation.

仪器功能描述：可见光成像系统（VIS）由三台弱光相机组成。其中两台相机共享主光学系统及部分次光学系统，用于获取可见光波段下的夜间极光卵图像。第三台相机用于监测极光相机相对于受日照地球的视场方向，并获取紫外波段下的全球极光卵图像。该VIS仪器每约24秒生成一张256×256像素的极光图像，生成间隔取决于所选的积分时间与滤镜。两台夜间极光相机的视场分别为：低分辨率相机5.6°×6.3°，中分辨率相机2.8°×3.3°。中分辨率相机从未启用。地球相机每5分钟生成一张或多张256×256像素的图像，具体数量取决于受控工作模式。地球相机的视场约为20°×20°。详见：http://vis.physics.uiowa.edu/vis/vis_description/vis_description.htmlx 参考文献：Frank, L.A.、J.B. Sigwarth、J.D. Craven、J.P. Cravens、J.S. Dolan、M.R. Dvorsky、J.D. Harvey、P.K. Hardebeck和D. Muller，《极地航天器可见光成像系统（VIS）》，《空间科学评论》，第71卷，第297-328页，1995年。

数据集描述：VIS地球相机数据集包含选定时间段内的全部地球相机图像。数据集包含用于确定观测者方位的完整坐标信息。此外，还提供旋转矩阵与畸变校正视向单位向量表，用于计算每个像素的坐标。为便于图像浏览，每张图像将附带基于所选滤镜特性的像素值至推荐色表的映射关系。可通过未压缩计数表获取相对强度标尺。强度表中给出了以千瑞利（kiloRayleighs）为单位的近似强度等级。如需获取强度的详细信息，请访问https://cdaweb.gsfc.nasa.gov/Polar_VIS_docs/SENSITIVITIES_AND_INTENSITIES.TXT查看Sensitivities_and_Intensities.txt文件。配套软件可通过以下地址获取：http://vis.physics.uiowa.edu/vis/software/ 该软件包含交互式数据语言（Interactive Data Language，IDL）程序，可加载推荐色棒显示图像、提供近似强度信息与各像素的坐标数据，并支持多种图像操作选项。