1. Intro

Why do we use RS?

• We can sample large scale observations and relatively quickly
• Many environmental phenomena vary significantly in both space and time
• In-situ measurements are lacking in many areas of the globe (mountains, less developed countries, etc.)

⭐What are the key requirements of RS?

• Energy source
• Instrument (sensor) and platform (ground based, airborne or satellite)
• Media transfer
• Relationship between variable of interest and electromagnetic (EM) measurement
• Unique solution

Classification

Passive v Active

• Active: provide their own source of energy to illuminate the objects they observe
• Passive: detect natural energy that is emitted or reflected by the object being observed. Reflected sunlight is the most common source of radiation measured by passive sensors.

Orbit

• Near-Polar Orbiting: Satellite that passes over, or very close to both poles Sun-synchronous orbits 是其中一个特例 polar orbit where the satellite passes over a location everyday at the same local solar time
• Geosynchronous: Orbit around the equator in the same direction/speed as the Earth rotates Geostationary satellites 是其中一个特例 Regional views of full earth disk. Continuous coverage always over the same region. Over the equator, altitude 35000 km