MODIS/Terra Calibrated Radiances 5-Min L1B Swath 250m - NRT

The 250 meter MODIS Level 1B Near Real Time (NRT) data set contains calibrated and geolocated at-aperture radiances for 2 discrete bands located in the 0.62 to 0.88 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). Additional data are provided including quality flags, error estimates and calibration data.
Channel locations for the MODIS 250 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

Separate L1B products are available for the five 500m resolution channels (MOD02HKM) and the twenty-nine 1km resolution channels (MOD021KM). For the 500m product, there are actually seven channels available since the data from the two 250 m channels have been aggregated to 500m resolution. Similarly, for the 1km product, all 36 MODIS channels are available since the data from the two 250m and five 500m channels have been aggregated into equivalent 1km
pixel values.

Spatial resolution for pixels at nadir is 250 m, degrading to 1.2 km in the along-scan direction and 0.5 km in the along-track direction for pixels located at the scan extremes. 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 250 m granule will contain a scene built from 203 scans sampled 5416 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 40 along-track spatial elements for the 250 m channels, the scene will be composed of (5416 x 8120) 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 17 degrees scan angle.

The Shortname for this product is MOD02QKM and is stored in the Earth Observing System Hierarchical
Data Format (HDF-EOS). A typical file size will be approximately 140 MB and the total daily volume is around 22GB.

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.

See the MODIS Characterization Support Team webpage for more C6 product information at:

http://mcst.gsfc.nasa.gov/l1b/product-information

or visit Science Team homepage at:
http://modis.gsfc.nasa.gov/data/dataprod/

该250米MODIS一级B近实时（NRT）数据集包含了电磁波谱0.62至0.88微米区域内的两个离散波段经校准和地理定位的入射辐射亮度。这些数据源自MODIS一级A扫描的原始辐射亮度，并在处理过程中转换为物理单位W / (m² μm sr)。此外，还提供了质量标志、误差估计和校准数据。MODIS 250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

对于五个500米分辨率通道（MOD02HKM）和二十九个1公里分辨率通道（MOD021KM），分别提供了独立的L1B产品。对于500米产品，实际上有七个通道可用，因为来自两个250米通道的数据已聚合到500米分辨率。同样，对于1公里产品，所有36个MODIS通道均可用，因为来自两个250米和五个500米通道的数据已聚合到等效的1公里像素值。

在正下方像素的空间分辨率为250米，沿扫描方向退化至1.2公里，沿轨道方向退化至0.5公里，对于位于扫描极端位置的像素。在地球观测系统（EOS）的705公里轨道上，55度的扫描模式导致2330公里的轨道条带宽度，并确保每1至2天实现全球覆盖。单个MODIS一级B 250米数据块将包含由203个扫描组成的一景，这些扫描在横跨轨道方向上被采样5416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250米通道的40个沿轨道空间元素，该景将由（5416 x 8120）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，扫描重叠将在大约17度扫描角度后增加。

该产品的简称是MOD02QKM，并存储在地球观测系统分层数据格式（HDF-EOS）中。典型文件大小约为140 MB，每日总量约为22GB。

从MODIS一级B测量中提取的环境信息将为全球范围内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、大气和海洋现象学研究视角。

更多信息请访问MODIS特征支持团队网页：
http://mcst.gsfc.nasa.gov/l1b/product-information

或访问科学团队主页：
http://modis.gsfc.nasa.gov/data/dataprod/