The international Network for the Detection of Atmospheric Composition Change (NDACC) is composed of more than 70 globally distributed, ground-based, remote-sensing research stations with more than 160 currently active instruments. The repository is intended to, among other objectives, detect changes and trends in atmospheric composition and to understand their impacts on the mesosphere, stratosphere, and troposphere; to provide critical data sets to help fill gaps in satellite observations; and to provide validation and development support for atmospheric models.