Welcome to the Earthdata Forum! Here, the scientific user community and subject matter experts from NASA Distributed Active Archive Centers (DAACs), and other contributors, discuss research needs, data, and data applications.
The way the gas correction is applied. If gas_opt=16, an implementation of ATREM is used. It is intended only for hyperspectral sensors with bands that can include significant gaseous absorption - particularly water vapor. Most sensors supported by l2gen do not require (or can even make use of) this option.