Remote sensing instruments measure energy between specific parts of the electromagnetic spectrum called ‘wavelengths’. Data collected between specific wavelengths are referred to as a 'band'. A single band looks like a black
and white photograph.
Some sensors can collect a number of different bands at the same time. These are called multi-spectral: multi means 'some' and spectral means 'coming from the electromagnetic spectrum'. Data from different bands can be combined to produce images that look like colour photographs. If the wavelengths are from the visible spectrum they can look like photographs you take with your own camera.
The way different objects reflect the energy from the sun is called their 'spectral signature'. The more sensitively we measure this signature the more we can tell about the object. Some sensors are designed to measure the spectral signature in very fine detail and these are known as hyper-spectral: hyper means 'many'. You can see the different information in the spectral signatures of a black and white photograph, a colour photograph and a scientific (hyperspectral) image. The hyperspectral images can tell us about the types of plants and rocks and under the right conditions the health of plants. By using data outside the visible we can understand a lot more about the environment which includes archaeology.