Hydrothermal alteration mapping

Mohammed Jalal Tazi

Salam Alaikum

Here are some of the best satellites for mapping hydrothermal alteration and the factors that influence the choice:

Best Satellites for Hydrothermal Alteration Mapping

Landsat 8 and Landsat 9:Spectral Resolution: Landsat 8 and 9 offer 11 spectral bands, including visible, near-infrared (NIR), shortwave infrared (SWIR), and thermal infrared (TIR) bands. The SWIR bands are particularly useful for identifying minerals associated with hydrothermal alteration. Spatial Resolution: 30 meters for most bands, 15 meters for the panchromatic band, and 100 meters for thermal bands. Temporal Resolution: 16-day revisit cycle.

Sentinel-2:Spectral Resolution: Sentinel-2 has 13 spectral bands, with bands in the visible, NIR, and SWIR regions. The SWIR bands are essential for detecting alteration minerals. Spatial Resolution: 10 meters for visible and NIR bands, 20 meters for red-edge and SWIR bands, and 60 meters for atmospheric correction bands. Temporal Resolution: 5-day revisit cycle when combining Sentinel-2A and 2B.

ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer):Spectral Resolution: ASTER provides 14 bands in visible, NIR, SWIR, and TIR regions. Its high spectral resolution in the SWIR region (6 bands) is particularly advantageous for hydrothermal alteration studies. Spatial Resolution: 15 meters for visible and NIR bands, 30 meters for SWIR bands, and 90 meters for TIR bands. Temporal Resolution: Variable, generally 16 days.

Hyperion (EO-1):Spectral Resolution: Hyperion offers 220 spectral bands covering the visible to shortwave infrared range (0.4 to 2.5 µm). This high spectral resolution allows for detailed identification of alteration minerals. Spatial Resolution: 30 meters. Temporal Resolution: Hyperion is no longer operational, but historical data can be valuable for research.

Factors Influencing the Choice of Satellite

Spectral Resolution:Importance: High spectral resolution, particularly in the SWIR region, is crucial for identifying specific minerals associated with hydrothermal alteration, such as clays, carbonates, and sulfates. Example: ASTER and Hyperion are preferred for their extensive spectral bands in the SWIR region.

Spatial Resolution:Importance: The spatial resolution determines the level of detail that can be resolved in the imagery. For detailed mapping of small-scale alteration features, higher spatial resolution is beneficial. Example: Sentinel-2 and Landsat 8/9 offer relatively high spatial resolution suitable for regional studies.

Temporal Resolution:Importance: Frequent revisit times are essential for monitoring changes over time and capturing data during optimal conditions. Example: Sentinel-2 has a short revisit time, making it ideal for time-sensitive studies.

Availability and Accessibility:Importance: The availability of data and ease of access can significantly impact the choice of satellite. Free and open-access data allow for more extensive and cost-effective research. Example: Landsat and Sentinel-2 data are freely available through platforms like the USGS Earth Explorer and Copernicus Open Access Hub.

Historical Data:Importance: Access to historical data can help in understanding long-term changes and trends in hydrothermal alteration. Example: Landsat has a long historical archive dating back to the 1970s, providing valuable temporal coverage.

Recommendations

For Regional Mapping: Sentinel-2 is a strong choice due to its good balance of spectral and spatial resolution, frequent revisit times, and free access.
For Detailed Mineral Identification: ASTER is recommended for its superior spectral resolution in the SWIR region, essential for detecting specific alteration minerals.
For Historical Analysis: Landsat's extensive historical archive makes it suitable for studies requiring long-term temporal analysis.
For High Spectral Resolution Needs: Although no longer operational, Hyperion data can be highly valuable for detailed spectral analysis of historical events.

Please recommend this reply if you find it useful . Thanks

Youssef Bammou

The choice of satellite data for mapping hydrothermal alteration depends mainly on three important factors

1- The availability of open-access data

2- The number of stock bands (spectral resolution)

3- Spatial resolution

See this link: https://www.indexdatabase.de/

Slimane Sassioui

Two important factors influence the choice of satellites.

The first is that the satellite meets our objectives, and the second is availability and accessibility.

For hydrothermal mapping, I think ASTER is the right choice

it offers us 14 spectral bands, including 6 SWIR, useful for mapping hydrothermal alteration, and it's available free of charge.

Ahmed I. Salem

ASTER can be your best choice

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