MOD021KM - Level 1B Calibrated Radiances - 1km

"The MODIS Level-1B data set contains calibrated and geolocated at-aperture radiances for 36 discrete bands located in the 0.4 µm to 14.4 µm region of the electromagentic spectrum. These data are generated from MODIS Level-1A scans of raw radiance, and in the process are converted to geophysical units of W/(m² µm sr). In addition, the Bidirectional Reflectance Distribution Function (BRDF) may be determined for the solar reflective bands (1-19, 26) 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.

The resolution of channels 1 and 2 is 250 m, channels 3 through 7 are 500m resolution, and the rest are 1 km resolution. However, for the MODIS L1B 1 km product, the 250 m and 500 m band radiance data and their associated uncertainties have been aggregated to 1 km resolution. Thus, the entire channel data set is referenced to the same spatial and geolocation scales. Separate L1B products are available for just the 250 m channels (MOD02QKM) and the 500 m channels (MOD02HKM) that preserve the original resolution of the data.

Spatial resolution for pixels at nadir is 1 km, degrading to 4.8 km in the along-scan direction at the scan extremes. However, thanks to the overlapping of consecutive swaths and the respective pixels there, the resulting resolution at the scan extremes is about 2 km. A 55 degree scanning pattern at the EOS orbit of 705 km results in a 2330 km orbital swath width with global coverage every one to two days. A single MODIS Level-1B granule will nominally contain a scene built from 203 scans (or swaths) sampled 1354 times in the cross-track direction, corresponding to approximately 5 minutes worth of data. Since an individual MODIS scan (or swath) will contain 10 along-track spatial elements, the scene will be composed of 1354 by 2030 pixels, resulting in a spatial coverage of 2330 km by 2030 km. Due to the MODIS scan geometry, there will be increasing overlap occurring beyond about a 25 degree scan angle.

Users requiring the full-resolution geolocation and solar/satellite geometry can obtain the separate MODIS Level-1 Geolocation product (MOD03) from LAADS."