Space Imaging Satellites: Landsat Series, Sentinel & High-Res Constellations

Explanation

The Landsat and Sentinel programs form the backbone of modern Earth observation. Sentinel-2 features three red-edge bands specifically tuned for measuring plant chlorophyll concentrations and leaf area index (LAI). When detailed site engineering demands sub-meter resolution, commercial satellite constellations utilize agile control-moment gyroscopes to point off-nadir, capturing stereoscopic image pairs used to compute highly accurate Digital Surface Models (DSMs).

Key points

• Copernicus Sentinel Program (ESA): Sentinel-1 (C-Band Synthetic Aperture Radar - all-weather SAR), Sentinel-2 (Multispectral Instrument - 13 spectral bands at 10m, 20m, 60m).
• Commercial High-Resolution Satellites: IKONOS (1999, first 1m commercial satellite), QuickBird, WorldView series (0.3m panchromatic, 1.2m multispectral), PlanetScope (flock of 200+ CubeSats providing daily 3m global imaging).
• Panchromatic Sharpening (Pan-sharpening): Merging high-resolution panchromatic band with lower-resolution multispectral bands to generate a sharp color composite.
• Open Data Revolution: Free public access to Landsat and Sentinel archives accelerating global environmental research and AI applications.

Example

Code examples

/*
Sentinel-2 vs Landsat 8/9 Comparison:
Sensor Specification | Sentinel-2 (MSI)              | Landsat 8/9 (OLI/TIRS)
Spatial Resolution   | 10m (VNIR), 20m (Red-Edge/SWIR)| 30m (VNIR/SWIR), 15m (Pan)
Number of Bands      | 13 spectral bands             | 11 spectral bands
Revisit Time         | 5 days (constellation of 2)   | 16 days (8 days with L8+L9)
Data Policy          | Free and Open (Copernicus)    | Free and Open (USGS)
*/

Exam questions

• [8 Marks] Describe the sensor payload, spectral bands, and capabilities of Landsat 8/9 (OLI/TIRS) and Sentinel-2 (MSI).
• [6 Marks] What is Pan-sharpening? Explain how combining panchromatic and multispectral bands produces high-resolution imagery.