Dobson spectrophotometers  can be used to measure both total column ozone and profiles of ozone in the atmosphere. Ozone is tri-atomic oxygen, O3; ozone molecules absorb harmful UV light in the atmosphere before it reaches the surface of the earth.
Dobson spectrophotometers can be used to measure both total column ozone and profiles of ozone in the atmosphere. Ozone is made up of three oxygen atoms, O3; ozone molecules absorb harmful UV light in the atmosphere before it reaches the Earth's surface.