The Light Detection and Ranging (LIDAR) instrument to measure the parameters needed to understand physics and chemistry in the atmosphere.
By analogy with common things, we will understand two important parts in the operation of the Lidar, measuring the distance and measuring the density of what is being measured. For ozone, for example, density is the number of molecules contained in the atmosphere at an altitude (distance from the ground) z.
The Lidar, in English Light Detection and Ranging makes it possible to measure many things in the atmosphere of the Earth but also of other planets: the ozone, the temperature, the dust, the clouds etc ... One emits towards the sky a radius Green (or blue, or red or invisible to the eye) and we look at the amount of light that is diffused through the atmosphere. In this way, several properties are deduced at each altitude, following a measurement principle that we will describe in this lesson.