After WorldView-3: a 2–4 m SWIR path for mineral mapping
Hydrothermal alteration mapping is the foundation of mineral-exploration targeting. For a decade it effectively required tasking one satellite — WorldView-3 — for its shortwave-infrared (SWIR) bands. WV-3 reached end of life in December 2025 with no like-for-like replacement. Here is why that matters and what a practical alternative looks like.
What alteration mapping actually needs
Two wavelength regions carry the diagnostic signal. The SWIR (roughly 2.0–2.4 µm) responds to hydroxyl-bearing clays and carbonates — the alteration halos around many ore systems. The visible-to-near-infrared (VNIR) discriminates iron species. Miss either and the map loses its interpretive power.
Resolution decides what you can classify. Fault-hosted alteration corridors, small outcrops, concentric zoning and excavation scars are diagnostic of structural control and hydrothermal centres — but they are sub-pixel noise at 10–20 m. You need a few metres to resolve them.
The Sentinel-2 route at 2–4 m
Each Sentinel-2 acquisition carries ten calibrated bands from visible through red-edge to two SWIR channels. EarthToDate enhances four bands to 2 m and six — including both SWIR bands — to 4 m, preserving radiometric integrity so derived indices stay physically meaningful.
From that stack come four alteration indices (ferric iron, iron-species discrimination, hydroxyl/clay, ferrous/propylitic), an adaptive composite score, temporal confidence layers, and a seven-class alteration map — worldwide, from an archive back to 2017, with no tasking queue and no per-scene fee. Sentinel-2's narrow VNIR bands even out-discriminate WV-3 for iron species, and a B12 SWIR product at sub-5 m now exists nowhere else commercially.
Honest limits
This is multispectral, not hyperspectral: it will not speciate minerals the way an airborne imaging spectrometer (AVIRIS-class) can. And 4 m SWIR is coarser than WV-3's native SWIR. What it offers instead is consistency, global coverage, a deep free-cadence archive, and reproducible indices — the difference between a one-off tasked collection and an operational layer you can re-run anywhere.