A lithographic apparatus comprising a projection system comprising at least one optical component and configured to project a pattern onto a substrate. The lithographic apparatus further comprises a control system arranged to reduce the effects of heating and/or cooling of an optical component in a lithographic process. The control system is configured at least: to select at least one of a plurality of mode shapes to represent a relationship between at least one input in the lithographic process and an aberration resulting from the input and to generate and apply a correction to the lithographic apparatus based on the mode shape.