ASTER L2 Surface Reflectance (AST_07XT)

ASTER L2 Surface Reflectance (AST_07XT V004) is the atmospherically corrected surface reflectance product derived from the ASTER instrument aboard Terra, covering nine bands across the VNIR and SWIR subsystems from 520 to 2430 nm.^[1] The current version (V004) uses MERRA-2 atmospheric modelling and is delivered as Cloud Optimized GeoTIFF; V003 in HDF-EOS2 format was decommissioned December 15, 2025.^[2] Distribution is via LP DAAC on an on-demand, per-scene ordering basis under an open NASA EOSDIS licence.^[1]

Spatial resolution differs by subsystem: VNIR bands 1 through 3N at 15 m, SWIR bands 4 through 9 at 30 m.^[1] The product row carries a 30 m native GSD, representing the SWIR subsystem that defines the mineral-mapping capability of the product.

Primary use is SWIR alteration-mineral mapping for hydrothermal systems, porphyry copper, and epithermal gold targets: clay, carbonate, sulphate, and phyllosilicate discrimination using SWIR bands 4-9.^[1] VNIR bands remain available for structural geology and vegetation-contrast mapping. ASTER SWIR data at 30-metre scale is a reference dataset for spaceborne mineral alteration mapping.^[3]

All SWIR mineral-mapping work draws on the 2000-2008 archive: anomalous saturation and striping began approximately April 2008, and the SWIR detector failed entirely January 12, 2009. Data from April 2008 through January 11, 2009 carry artefacts and should not be used for quantitative reflectance analysis.^[1] VNIR acquisition continued after the SWIR failure. Users must order the crosstalk-corrected AST_07XT product rather than AST_07 for quantitative mineral mapping, as the former applies scattering correction between SWIR bands.^[1] A 60 km swath width limits individual-target revisit density within the archive. NASA Earthdata account registration is required for ordering.