Active support scheme may decide the deformation of the optical surface figure of

the primary mirror. Two main active axial support schemes are often adopted to the thin meniscus primary mirror, one scheme is that the axial supports normal to the mirror bottom surface, and the other is that the active forces parallel to the optical axis. In order to compare the performance of the two support schemes, 1-m thin meniscus primary mirror is conducted. Finite element analysis (FEA) is employed to analyze the optical surface figures of the primary mirror, and optimizations are carried out by using ANSYS for each support scheme to obtain the locations and active forces.

The axial support force sensitivities are calculated for the two support schemes in a case that a single axial support has a force error of 0.5 N. The correction ability of the active support system for both of the support schemes are analyzed when an arbitrary axial support is failure. Several low order Zernike modes are modeled with MATLAB procedure, and active optics corrections are applied to these modes for the two active supports. The extra mirror surface error due to thermal deformation is also corrected with the two support schemes.