ATCOR is not an Exelis VIS product, and does not plug in to IDL or ENVI. You may want to contact Geosystems for information about ATCOR. ENVI does have a similar atmospheric correction module, which includes the FLAASH and QUACC atmospheric correction tools. You can find more information about that here: https://www.exelisvis.com/ProductsServices/ENVI/ACM.aspx - Peg Exelis VIS