Chapter 11

Satellite Systems Overview

Over 1,000 Earth observation satellites orbit our planet, each designed for specific missions from weather monitoring to sub-meter urban mapping.

USGS Earth ExplorerCopernicus Open HubGoogle Earth EngineSNAPPlanet Explorer

1,000+EO Satellites↗ In orbit 2024

~7,000 imagesSentinel-2/Day↗ 1.6 TB daily

Theory & Foundations

Satellites are classified by orbit type (LEO, MEO, GEO), sensor type (optical, SAR, thermal), and mission (weather, land, ocean, atmosphere).

Low Earth Orbit (LEO, 200–2000km): Most EO satellites. Landsat (705km), Sentinel (786km). Higher resolution but limited coverage per pass.

Geostationary (GEO, 35,786km): Weather satellites (GOES, Meteosat) providing continuous hemisphere coverage at ~1km resolution.

Sun-Synchronous Orbit: Special LEO crossing equator at same local time, ensuring consistent illumination. Used by most EO satellites.

Major free missions: Landsat (30m, 16-day, since 1972), Sentinel-2 (10m, 5-day), Sentinel-1 SAR (all-weather), MODIS (daily global at 250m–1km).

In-Depth Coverage

Free Satellite Missions

Government-funded programs providing freely accessible data.

Landsat (USGS/NASA): 30m, 16-day, 11 bands, since 1972
Sentinel-2 (ESA): 10m, 5-day, 13 bands — best free optical
Sentinel-1 (ESA): SAR, 12-day, all-weather radar
MODIS (NASA): 250m–1km, daily — climate and fire

Commercial Satellites

Private companies provide sub-meter imagery.

Maxar (WorldView-3): 30cm, 8 VNIR + 8 SWIR bands
Planet (SkySat): 50cm, video capability
Planet (Dove): 3m daily global "scan of Earth"

Key Techniques

Data search and downloadCloud cover filteringRadiometric calibrationAtmospheric correctionComposite creation

Data Visualization

Research Publications by Platform (thousands)

Landsat50

Sentinel-238

MODIS30

Sentinel-125

Satellite Orbits

🛰️LEO200–2000km: EO satellites
📍MEO2000–35,786km: GNSS
🌤️GEO35,786km: Weather

Practical Workflow

Define observation requirements
Search data archives with spatial/temporal filters
Evaluate cloud cover in metadata
Download and verify quality
Apply radiometric calibration
Perform atmospheric correction
Create composites for analysis
Archive with metadata documentation

Software & Tools

USGS Earth ExplorerFreeWeb Portal — Download Landsat and SRTM data

Video Tutorials

▶ Satellite Remote Sensing OverviewESA · YouTube · 20 min

Real-World Application

During Bangladesh 2020 floods, Sentinel-1 SAR provided the only viable imagery through clouds. ESA Copernicus EMS produced flood maps guiding relief for BDRCS.

Real-World Projects

Bangladesh Flood SAR Mapping📍 Bangladesh

Sentinel-1 flood mapping during 2020 monsoon.

Impact: Maps guided relief for 5M+ affected people.

Case Study

Planet Labs operates 200+ Dove satellites achieving daily 3m global coverage. Global Forest Watch partnership provides near-real-time deforestation alerts.

Problem-Based Learning

P1 Compare 20-year urban expansion

City planning needs urban sprawl quantification.

Solution: Use Landsat 5 TM (2000) and Landsat 9 (2023). Classify urban/non-urban. Calculate change.

USGS Earth ExplorerGEERandom Forest

✅ Mapped 340% urban expansion, informing new zoning regulations.

Knowledge Check

1. Best free 10m optical satellite?