Calibration of MEMS DM actuator gains using a Zernike wavefront sensor on the HiCAT testbed and implications for Habitable Worlds Observatory operations

Deformable mirrors (DMs) are critical for coronagraph operations on ground-based telescopes and future missions like HWO and Roman CGI. They enable wavefront control to create a high-contrast “dark zone” (DZ) for detecting faint companions. Achieving contrasts <1e-8 requires precise DM actuator-gain calibration, as picometer-level errors degrade DZ digging efficiency, increase overheads, and tighten stability requirements. Because DM gain varies with stroke, rapid in situ recalibration is needed. Zernike wavefront sensors (ZWFS) offer picometer sensitivity and will likely be onboard HWO, but their use for DM calibration remains unproven and has major operational implications. We present HiCAT testbed results calibrating gain maps for two 952-actuator BMC MEMS DMs with both a Fizeau interferometer and a ZWFS. We show that the ZWFS achieves sub-nm sensitivity and supports gain maps using local linear or quadratic models with implications for final DZ contrast and digging efficiency.