Method for calibrating a manipulator

The invention relates to an iterative method for calibrating a manipulator (600) of a projection objective (700) for microlithography, wherein The manipulator causes a change in an aberration error of the projection lens by changing at least one surface and / or a refractive index distribution of an optical element, - This change is effected by means of a spatially resolved temperature control of the optical element (601), - At least one iteration step is performed, wherein this iteration step - The collection of a manipulator state vector, which describes the optical effect of the manipulator (600), and - The calculation of a travel command using a Stellwegsgenerierenden method based on the manipulator state vector and predetermined specification values, and The control of the manipulator (600) according to the calculated travel command.