Lecture 20

• there are many Earth Observation Satellites in orbit
• satellites allow us yo make all kinds of interesting observations
• passive sensors record electromagnetic radiation being reflected off the earth
• active sensors send electromagnetic radiation towards the earth and record what bounces back
• the sensors detect electromagnetic radiation. Visible light is only a tiny fraction of the spectrum
• optical satellites


  capture spectral bands on the visible spectrum, with some capabilities at wavelengths just shorter and longer than visible
• a 'band' is just a dataset consisting of one wavelength on the electromagnetic spectrum
• your typical 'satellite image' (say on google maps) is a combination of the red, green and blue bands
• if you do some maths with the bands you can learn all kinds of interesting things
• radar


  it can see through clouds. Depending on the wavelength it can see through trees. Used for biomass, water and interferometry
• radar interferometry


  you can measure centimetre scale changes from orbit
• lidar


  shoots a laser that bounces back
• you can make an estimate for GHG emissions from biomass estimates