MODIS/Aqua Calibrated Radiances 5-Min L1B Swath 500m - NRT

The 500 meter MODIS Level 1B Near Real Time (NRT) data set contains calibrated and geolocated at-aperture radiances for 7 discrete bands located in the 0.45 to 2.20 micron region of the electromagnetic spectrum. These data are generated from the MODIS Level 1A scans of raw radiance and in the process converted to geophysical units of W/(m^2 um sr). In addition, the Earth Bi-directional Reflectance Distribution Function (BRDF) may be determined for these solar reflective bands through knowledge of the solar irradiance (e.g., determined from MODIS solar diffuser data, and from the target illumination geometry). Additional data are provided including quality flags, error estimates and calibration data. Visible, shortwave infrared, and near infrared measurements are only made during the daytime, while radiances for the thermal infrared region (bands 20-25, 27-36) are measured continuously. Channel locations for the MODIS 500 meter data are as follows: Band Center Wavelength (um) Primary Use ---- ---------------------- ----------- 1 0.620 - 0.670 Land/Cloud Boundaries 2 0.841 - 0.876 Land/Cloud Boundaries 3 0.459 - 0.479 Land/Cloud Properties 4 0.545 - 0.565 Land/Cloud Properties 5 1.230 - 1.250 Land/Cloud Properties 6 1.628 - 1.652 Land/Cloud Properties 7 2.105 - 2.155 Land/Cloud Properties Channels 1 and 2 have 250 m resolution, channels 3 through 7 have 500 m resolution. However, for the MODIS L1B 500 m product, the 250 m band radiance data and their associated uncertainties have been aggregated to 500 m resolution. Thus the entire channel data set has been co-registered to the same spatial scale in the 500 m product. Separate L1B products are available for the 250 m resolution channels (MYD02QKM) and 1 km resolution channels (MYD021KM). For the latter product, the 250 m and 500 m channel data (bands 1 through 7) have been aggregated into equivalent 1 km pixel values. Spatial resolution for pixels at nadir is 500 km, degrading to 2.4 km in the along-scan direction at the scan extremes. However, thanks to the overlapping of consecutive swaths and respectively pixels there, the resulting resolution at the scan extremes is about 1 km. A 55 degree scanning pattern at the EOS orbit of 705 km results in a 2330 km orbital swath width and provides global coverage every one to two days. A single MODIS Level 1B 500 m granule will contain a scene built from 203 scans sampled 2708 times in the cross-track direction, corresponding to approximately 5 minutes worth of data; thus 288 granules will be produced per day. Since an individual MODIS scan will contain 20 along-track spatial elements for the 500 m channels, the scene will be composed of (2708 x 4060) pixels, resulting in a spatial coverage of (2330 km x 2040 km). Due to the MODIS scan geometry, there will be increasing scan overlap beyond about 20 degrees scan angle. To summarize, the MODIS L1B 500 m data product consists of: 1. Calibrated radiances, uncertainties and number of samples for (2) 250 m reflected solar bands aggregated to 500 m resolution 2. Calibrated radiances and uncertainties for (5) 500 m reflected solar bands 3. Geolocation for 1km pixels, that must be interpolated to get 500 m pixel locations. For the relationship of 1km pixels to 500m pixels, see the Geolocation ATBD http://modis.gsfc.nasa.gov/data/atbd/atbd_mod28_v3.pdf . 4. Calibration data for all channels (scale and offset) 5. Comprehensive set of file-level metadata summarizing the spatial, temporal and parameter attributes of the data, as well as auxiliary information pertaining to instrument status and data quality characterization The MODIS L1B 500 m data are stored in the Earth Observing System Hierarchical Data Format (HDF-EOS) which is an extension of HDF as developed by the National Center for Supercomputer Applications (NCSA) at the University of Illinois. A typical file size will be approximately 170 MB. Environmental information derived from MODIS L1B measurements will offer a comprehensive and unprecedented look at terrestrial, atmospheric, and ocean phenomenology for a wide and diverse community of users throughout the world. The Shortname for this product is MYD02HKM

该500米MODIS一级B近实时（NRT）数据集包含了电磁谱0.45至2.20微米区域内7个离散波段经过校准并地理定位的孔径辐射亮度。这些数据由MODIS一级A扫描的原始辐射亮度生成，并在过程中转换为物理单位W/(m^2 um sr)。此外，通过了解太阳辐照度（例如，从MODIS太阳漫射器数据及目标照明几何形状中确定），可以确定这些太阳反射波段的大气双向反射率分布函数（BRDF）。此外，还提供了包括质量标志、误差估计和校准数据在内的附加数据。可见光、短波红外和近红外测量仅在白天进行，而热红外区域（波段20-25，27-36）的辐射亮度则持续测量。MODIS 500米数据的通道位置如下：波段 中心波长（um） 主要用途 ---- ---------------------- ----------- 1 0.620 - 0.670 陆地/云边界 2 0.841 - 0.876 陆地/云边界 3 0.459 - 0.479 陆地/云特性 4 0.545 - 0.565 陆地/云特性 5 1.230 - 1.250 陆地/云特性 6 1.628 - 1.652 陆地/云特性 7 2.105 - 2.155 陆地/云特性 通道1和2具有250米分辨率，通道3至7具有500米分辨率。然而，对于MODIS L1B 500米产品，250米波段辐射亮度数据及其相关不确定性已汇总至500米分辨率。因此，整个通道数据集已在500米产品中进行了空间尺度的一致化。此外，还提供了针对250米分辨率通道（MYD02QKM）和1公里分辨率通道（MYD021KM）的独立L1B产品。对于后者产品，250米和500米通道数据（波段1至7）已汇总为等效的1公里像素值。赤道下像素的空间分辨率为500公里，在扫描极端方向上降低至2.4公里。然而，由于连续条带及其相应像素的重叠，扫描极端方向上的分辨率约为1公里。EOS轨道上的55度扫描模式在705公里的轨道高度上产生2330公里的轨道条带宽度，并确保全球每1至2天覆盖一次。单个MODIS一级B 500米数据块将包含由203个扫描组成的一个场景，这些扫描在横切方向上采样2708次，相当于大约5分钟的数据；因此，每天将产生288个数据块。由于单个MODIS扫描将包含500米通道的20个沿切向空间元素，场景将由（2708 x 4060）像素组成，从而实现（2330 km x 2040 km）的空间覆盖。由于MODIS扫描几何形状，扫描角度超过约20度时，扫描重叠将逐渐增加。总之，MODIS L1B 500米数据产品包括：1. 将（2）个250米反射太阳波段汇总至500米分辨率的校准辐射亮度、不确定性和样本数量2. （5）个500米反射太阳波段的校准辐射亮度和不确定性3. 1公里像素的地理定位，该定位必须插值以获取500米像素位置。有关1公里像素与500米像素的关系，请参阅地理定位ATBD http://modis.gsfc.nasa.gov/data/atbd/atbd_mod28_v3.pdf4. 所有通道的校准数据（比例尺和偏移量）5. 一套完整的文件级元数据，总结数据的空间、时间和参数属性，以及与仪器状态和数据质量表征相关的辅助信息MODIS L1B 500米数据存储在地球观测系统层次数据格式（HDF-EOS）中，这是美国伊利诺伊大学国家超级计算应用中心（NCSA）开发的HDF的扩展。典型文件大小约为170 MB。从MODIS L1B测量中提取的环境信息将为全球广大且多样化的用户群体提供一个全面且前所未有的陆地、大气和海洋现象的视角。该产品的简称是MYD02HKM