Millimeter-level surface flatness is critical for spaceborne synthetic aperture radar deployable planar antennas to ensure high-resolution imaging performance. This study addresses the core challenge of maintaining flatness accuracy under multisource disturbances–including manufacturing/assembly errors and joint clearance–in a [Formula: see text] carbon-fiber-reinforced antenna with honeycomb panels. To overcome the progressive distortion of traditional finite element models (FEMs) in long error