Microwave Remote Sensing Overview
Introduction to Microwave Remote Sensing
- Importance of studying microwave remote sensing in hydrology
Historical Context
- Development of electricity, magnetism, and light since the 18th century
- Thomas Young's wave theory and the Young-Helmholtz theory on color
- Concept of interference of light demonstrated through the double-slit experiment
- Hans Christian Ørsted's discovery of the relation between electricity and magnetism
- Michael Faraday's work on induction relating electricity and magnetism
- Maxwell's equations unified electricity, magnetism, and light, introducing electromagnetic waves
Fundamentals of Waves
- Key parameters of waves:
- Amplitude: Maximum disturbance from the axis
- Frequency: Number of waves per unit time (unit: Hertz)
- Wavelength: Distance between successive crests or troughs
- Polarization: Direction of the electric field vector's oscillation
- Wave description: exists both as a wave and a flow of photons
Understanding Electromagnetic Radiation
- Defined as time-varying electric and magnetic fields
- Relation to the electromagnetic spectrum with a focus on microwaves (1mm to 30cm)
Microwave Remote Sensing
- Evolution during WWII for reconnaissance and development of radar technologies
- Use of various microwave bands: Ka, K, Ku, X, C, S, L, P bands
- Radars can penetrate clouds effectively
Remote Sensing Definitions
- Remote sensing involves measuring reflected or emitted electromagnetic radiation without direct contact with targets
- Categories:
- Active Remote Sensing: Sensor illuminates the target
- Passive Remote Sensing: Sensor measures naturally emitted/reflected radiation
Summary of Key Points
- Wave properties: amplitude, frequency, wavelength, polarization, and phase
- Electromagnetic spectrum and microwave characteristics
- Types of remote sensing with practical applications in hydrology
Next Steps
- Upcoming lectures will delve deeper into the fundamental properties of microwaves and their applications in hydrology.