MYD09A1 v006

MODIS/Aqua Surface Reflectance 8-Day L3 Global 500 m SIN Grid

PI: Eric Vermote

The MYD09A1 Version 6 data products was decommissioned on July 31, 2023. Users are encouraged to use the MYD09A1 Version 6.1 data product.


The Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua MYD09A1 Version 6 product provides an estimate of the surface spectral reflectance of Aqua MODIS Bands 1 through 7 corrected for atmospheric conditions such as gasses, aerosols, and Rayleigh scattering. Along with the seven 500 meter (m) reflectance bands are a quality layer and four observation bands. For each pixel, a value is selected from all the acquisitions within the 8-day composite period. The criteria for the pixel choice include cloud and solar zenith. When several acquisitions meet the criteria the pixel with the minimum channel 3 (blue) value is used.

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Improvements/Changes from Previous Versions

  • Improvements to the aerosol retrieval and correction algorithm along with new aerosol retrieval look-up tables.
  • Refinements to the internal snow, cloud, and cloud shadow detection algorithms. Uses Bidirectional Reflectance Distribution Function (BRDF) database to better constrain the different threshold used.
  • Processes ocean bands to create a new Surface Reflectance Ocean product and provides Quality Assurance (QA) datasets for these bands.
  • Improved discrimination of salt pans from cloud and snow, along with the inclusion of a salt pan flag in the QA band.

Product Maturity

Validation at stage 3 has been achieved for the MODIS Surface Reflectance products. Further details regarding MODIS land product validation for the MYD09 data product is available from the MODIS Land Team Validation site.

Collection and Granule


Characteristic Description
CollectionAqua MODIS
File Size59.16 MB
Temporal ResolutionMulti-Day
Temporal Extent2002-07-04 to 2023-02-26
Spatial ExtentGlobal
Coordinate SystemSinusoidal
File FormatHDF
Geographic Dimensions1200 km x 1200 km


Characteristic Description
Number of Science Dataset (SDS) Layers13
Columns/Rows2400 x 2400
Pixel Size500 m

Layers / Variables

SDS Name Description Units Data Type Fill Value No Data Value Valid Range Scale Factor
sur_refl_b01 Surface Reflectance Band 1 (620-670 nm) N/A 16-bit signed integer -28672 N/A -100 to 16000 0.0001
sur_refl_b02 Surface Reflectance Band 2 (841-876 nm) N/A 16-bit signed integer -28672 N/A -100 to 16000 0.0001
sur_refl_b03 Surface Reflectance Band 3 (459-479 nm) N/A 16-bit signed integer -28672 N/A -100 to 16000 0.0001
sur_refl_b04 Surface Reflectance Band 4 (545-565 nm) N/A 16-bit signed integer -28672 N/A -100 to 16000 0.0001
sur_refl_b05 Surface Reflectance Band 5 (1230-1250 nm) N/A 16-bit signed integer -28672 N/A -100 to 16000 0.0001
sur_refl_b06 Surface Reflectance Band 6 (1628-1652 nm) N/A 16-bit signed integer -28672 N/A -100 to 16000 0.0001
sur_refl_b07 Surface Reflectance Band 7 (2105-2155 nm) N/A 16-bit signed integer -28672 N/A -100 to 16000 0.0001
sur_refl_qc_500m Surface reflectance 500m band quality control flags Bit Field 32-bit unsigned integer 4294967295 N/A 0 to 4294966531 N/A
sur_refl_szen MODIS solar zenith angle Degree 16-bit signed integer 0 N/A 0 to 18000 0.01
sur_refl_vzen MODIS view zenith angle Degree 16-bit signed integer 0 N/A 0 to 18000 0.01
sur_refl_raz MODIS relative azimuth angle Degree 16-bit signed integer 0 N/A -18000 to 18000 0.01
sur_refl_state_500m Surface reflectance 500m state flags Bit Field 16-bit unsigned integer 65535 N/A 0 to 57343 N/A
sur_refl_day_of_year Day of the year for the pixel Julian day 16-bit unsigned integer 65535 N/A 1 to 366 N/A

Product Quality

The sur_refl_qc_500m and sur_refl_state_500m 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.

The quality bit flags for sur_refl_qc_500m and the sur_refl_state_500m are given in the User Guide in Tables 10 and 13.

Quality assurance information should be considered when determining the usability of data for a particular science application. The ArcGIS MODIS-VIIRS Python Toolbox contains tools capable of decoding quality data layers while producing thematic quality raster files for each quality attribute.

In addition to data access and transformation processes, AppEEARS also has the capability to unpack and interpret the quality layers.

Known Issues

The Collection 6 MODIS Land Surface Reflectance product (MYD09) 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 were implemented in Collection 6.1 reprocessing.

For complete information about the MYD09A1 known issues please refer to the MODIS Land Quality Assessment website.

About the image

Aqua MODIS surface reflectance band 1-4-3 data from the MYD09A1 product over western United States, July 28 - August 4, 2018.

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User Guide
Algorithm Theoretical Basis Document (ATBD)
File Specification

Using the Data

Access Data


DOI: 10.5067/MODIS/MYD09A1.006