The 250 meter MODIS Level-1B data set contains calibrated and geolocated at-aperture radiances for 7 discrete bands located in the 0.45 to 2.20 µm 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/(m2 µm sr). In addition, the Bidirectional 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.
Channel locations for the MODIS 250 m MYD02QKM product are 0.62 µm - 0.67 µm and 0.841 µm - 0.876 µm, the only bands in the MYD02 product that are 250m resolution.
Separate L1B products are available for the five 500 m resolution channels (MYD02HKM) and the twenty-nine 1 km resolution channels (MYD021KM). For the 500 m product, there are actually seven channels available since the data from the two 250 m channels have been aggregated to 500 m resolution. Similarly, for the 1 km product, all 36 MODIS channels are available since the data from the two 250 m and five 500 m channels have been aggregated into equivalent 1 km 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 by 8120 pixels, resulting in a spatial coverage of 2330 km by 2040 km. Due to the MODIS scan geometry, there will be increasing scan overlap beyond about a 17 degree scan angle.