transmission spectroscopy

Transmission spectroscopy is study of a substance through its effect on the spectrum of electromagnetic radiation (EMR) passing through. Absorption spectroscopy also fits this definition, but transmission spectroscopy typically means something more, such as the use of differential spectroscopy. In astronomy, the term is used sometimes for techniques analyzing of atmospheres, the interstellar medium, and clouds. It is one of the terms used for data collection regarding an extra-solar planet atmosphere through spectroscopy of the star's EMR that has passed through it.