The MOD09GA Version 6 product provides an estimate of the surface spectral reflectance of Terra Moderate Resolution Imaging Spectroradiometer (MODIS) Bands 1 through 7, corrected for atmospheric conditions such as gasses, aerosols, and Rayleigh scattering. Provided along with the 500 meter (m) surface reflectance, observation, and quality bands are a set of ten 1 kilometer (km) observation bands and geolocation flags. The reflectance layers from the MOD09GA are used as the source data for many of the MODIS land products.
|File Size||84 MB|
|Temporal Extent||2000-02-24 to Present|
|Geographic Dimensions||1200 km x 1200 km|
|Number of Science Dataset (SDS) Layers||22|
|Columns/Rows||2400 (500 m) and 1200 (1000 m) x 2400 (500 m) and 1200 (1000 m)|
|Pixel Size||500 m and 1000 m|
|SDS Name||Description||Units||Data Type||Fill Value||No Data Value||Valid Range||Scale Factor|
|num_observations_1km||Number of observations within a pixel||N/A||8-bit signed integer||-1||N/A||0 to 127||N/A|
|state_1km_1||1km Reflectance Data State QA||Bit Field||16-bit unsigned integer||65535||N/A||0 to 57335||N/A|
|SensorZenith_1||Zenith angle to sensor||Degree||16-bit signed integer||-32767||N/A||0 to 18000||0.01|
|SensorAzimuth_1||Azimuth angle to sensor||Degree||16-bit signed integer||-32767||N/A||-18000 to 18000||0.01|
|Range_1||Distance to sensor||Meters||16-bit unsigned integer||0||N/A||27000 to 65535||0.04|
|SolarZenith_1||Zenith angle to sun||Degree||16-bit signed integer||-32767||N/A||0 to 18000||0.01|
|SolarAzimuth_1||Azimuth angle to sun||Degree||16-bit signed integer||-32767||N/A||-18000 to 18000||0.01|
|gflags_1||Geolocation flags||Bit Field||8-bit unsigned integer||255||N/A||0 to 248||N/A|
|orbit_pnt_1||Orbit pointer||N/A||8-bit signed integer||-1||N/A||0 to 15||N/A|
|granule_pnt_1||Granule pointer||N/A||8-bit unsigned integer||255||N/A||0 to 254||N/A|
|num_observations_500m||Number of observations per 500m pixel||N/A||8-bit signed integer||-1||N/A||0 to 127||N/A|
|sur_refl_b01_1¹||Surface Reflectance for Band 1||N/A||16-bit signed integer||-28672||N/A||-100 to 16000||0.0001|
|sur_refl_b02_1¹||Surface Reflectance for Band 2||N/A||16-bit signed integer||-28672||N/A||-100 to 16000||0.0001|
|sur_refl_b03_1||Surface Reflectance for Band 3||N/A||16-bit signed integer||-28672||N/A||-100 to 16000||0.0001|
|sur_refl_b04_1||Surface Reflectance for Band 4||N/A||16-bit signed integer||-28672||N/A||-100 to 16000||0.0001|
|sur_refl_b05_1||Surface Reflectance for Band 5||N/A||16-bit signed integer||-28672||N/A||-100 to 16000||0.0001|
|sur_refl_b06_1||Surface Reflectance for Band 6||N/A||16-bit signed integer||-28672||N/A||-100 to 16000||0.0001|
|sur_refl_b07_1||Surface Reflectance for Band 7||N/A||16-bit signed integer||-28672||N/A||-100 to 16000||0.0001|
|QC_500m_1||Surface Reflectance 500m Quality Assurance||Bit Field||32-bit unsigned integer||787410671||N/A||0 to 4294966019||N/A|
|obscov_500m_1||Observation coverage||Percent||8-bit signed integer||-1||N/A||0 to 100||0.01|
|iobs_res_1||Observation number||N/A||8-bit unsigned integer||255||N/A||0 to 254||N/A|
|q_scan_1²||250m scan value information||N/A||8-bit unsigned integer||255||N/A||0 to 254||N/A|
¹Data layers sur_refl_b01_1 and sur_refl_b02_1 may not always be present.
²Description information for the q_scan_1 layer is given in Table 17 of the User Guide. Please note this layer may not be present in all products.
The state_1km_1 and QC_500m_1 layers are stored in an efficient bit-encoded manner. The unpack_sds_bits executable from the LDOPE tools is available to the user community to help parse and interpret these layers.
In addition to data access and transformation processes, AppEEARS also has the capability to unpack and interpret the quality layers.
The QA bit flags for the state_1km_1 and the QC_500m_1 layers are provided in the User Guide in Table 13 and 10 respectively.
Striping due to a dead detector is noticeable for bands 5, 6, and 7 in scenes acquired February 24 through October 31, 2000. Corrections were implemented to reduce the striping in data acquired after November 1, 2000. Users should always check the band quality for dead detectors even though reflectance values may be in the valid range.
The Collection 6 MODIS Land Surface Reflectance product (MOD09) may incorrectly flag retrievals as ‘High Aerosol’ over brighter surfaces and at higher view angles. This will impact the downstream MODIS BRDF/Albedo (MCD43) and Vegetation Index (MOD13 and MYD13) data products which use the aerosol quantity flag to screen out high aerosol values.
Corrections will be implemented in Collection 6.1 reprocessing in 2020.
For complete information about the MOD09GA known issues please refer to the MODIS Land Quality Assessment website.