 Two popular remote sensing methods used to estimate up-welling long-wave radiation are to estimate values using surface temperature and emissivity, and to estimate directly from satellite top-of-atmosphere radiance or brightness temperature.Measuring outgoing long-wave radiation at the top of atmosphere and down-welling long-wave radiation at the surface is important for understanding how much radiative energy is kept in our climate system, how much reaches and warms the surface, and how the energy in the atmosphere is distributed to affect developments of clouds.Calculating the long-wave radiative flux from a surface is also a useful an easy way to assess surface temperature

Outgoing long-wave radiation (OLR) has been monitored globally since 1975 by a number of successful and valuable satellite missions.