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We present the development status of our multi-conjugate adaptive optics (MCAO) system for monitoring observations of the solar system planets. This MCAO system is intended to improve the spatial resolution (several tenths of an arcsecond) of the planetary image over about 50-arcsec field of view in the visible wavelength (0.5 to 1μm) for 1.5-m class telescopes (1.6-m Pirka telescope of Hokkaido University and 1.5-m Kanata telescope of Hiroshima University) at the moderate seeing (1 to 2 arcsec) sites in Japan. The system has two 140-element MEMS deformable mirrors, which conjugate the telescope pupil and 2.6km altitude. The wavefronts are measured by the correlation tracking of the surface patterns on the planet such as the clouds of Jupiter, as similar in the solar adaptive optics systems but much lower surface brightness. Currently, the system has four 11×11- element Shack-Hartmann wavefront sensors (WFSs) with a field of view of about 16 x 16 arcsec, which can patrol a field of view of 60 × 60 arcsec entirety. However, the current performance of AO correction of this MCAO system is limited mainly due to the low frame rate and the somewhat large readout noise of the WFS cameras. In addition, the allowable field positions for wavefront measurements in the entire field of view are limited by vignetting due to the pyramid mirror (field splitter) at the front of WFSs. In order to improve the performance of AO correction, we will replace these four WFSs and the field splitter with a single wide-field 11×11-element Shack-Hartmann WFS with a field of view of 54 × 54 arcsec, a faster frame rate (≳ 500 fps), and a lower readout noise (∼ 2 e− rms). We describe the upgrade plan, design, expected performance, and current status of upgrade of our MCAO system.
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