Information for S24A applicants

Before preparing the proposal, please read Planning Observations very carefully .

LGS mode will be operated with TBAD (Shared-risk)

The new laser guide star (LGS) system for AO188 will be operated with TBAD (Transponder Based Aircraft Detector). Please note that the LGS mode with TBAD will be opened as a shared-risk policy. LGS mode can be used with IRCS and IRD. Note that all proposals requesting LGS mode observation should prepare a backup plan with NGS mode.

Near-Infrared wavefront sensor for AO188 (Shared-risk)

The near-infrared wavefront sensor (NIR WFS) of AO188 is open in shared risk mode, only for limited modes with IRCS and SCExAO/CHARIS. Please refer to the NIR WFS website and the IRCS webpage for more information. Users planning to submit a proposal MUST contact Dr. Julien Lozi (; the PI of the NIR WFS) and include him in the proposal as a Co-I.

If the following conditions apply to you, please contact the primary support astronomer in advance:

  • Those who intend to use the LGS mode for the first time
  • Those who want to observe with non-sidereal objects using the atmosperic dispersion corrector


AO188 is a curvature wavefront sensor based adaptive optics (AO) system. The curvature wavefront sensor is made of 188 photon counting APD modules that feed to a 188 element bimorph mirror. AO188 is installed at the IR Nasmyth platform of Subaru telescope and offers natural guide star (NGS) and laser guide star (LGS) modes.

The open-use instrument behind AO188 is IRCS. SCExAO, SCExAO+CHARIS, SCExAO+VAMPIRES, SCExAO+FPDI, SCExAO+MEC, IRD, and SCExAO+REACH are also available with AO188 as PI type instruments.

AO188 in the NGS mode has been offered for open use observations since S08B. The NGS mode requires a bright star within 30 arcsec from the science target. If your target itself is bright enough and not very extended, you can use it as a NGS. To obtain reasonable performance improvement, the NGS should be brighter than R magnitude of 16.5. Diffraction-limited spatial resolution can be achieved at KLM-band with a sufficiently bright guide star at good observing conditions. At shorter wavelength (zJH band), high spatial resolution comparable to or even higher than the K-band diffraction-limit resolution can be achieved. The maximum Strehl ratio so far achieved at K-band is 0.55 at a 0.5'' seeing condition.

LGS mode uses an artificial sodium laser guide star for high-order wavefront correction. Because an artificial guide star can be created close to or on top of the science target, better AO correction is expected using the LGS than a far away NGS.
Our LGS mode was first opened to public at the latter half of S11A semester. However, the brightness of the LGS degraded from R=10.5 (in 2011) to R=14 at EL=80 degree in January 2019. Due to this degradation, it was decided to upgrade the laser system.
The new laser system is based on the TOPTICA laser and the optics are composed of mirrors, which provides the LGS with the brightness of 8.5 -- 10.0 mag in R-band (see figure below). The bright LGS will increase the stability of the LGS-mode observations. The performance of the AO will be comparable to the old system since it depends on the ability of AO188. Please see the Performance page for the details.

Basic Instrument Parameters

System Overview


Planning Observations


Fits header

Instrument citation

Please cite the following paper when you refer AO188 in your publication.

"Commisioning status of Subaru laser guide sta adaptive optics system"
Hayano et al. 2010, Proc. SPIE, vol. 7736, 21
"Current status of the laser guide star adaptive optics system for Subaru Telescope"
Hayano et al. 2008, Proc. SPIE, vol. 7015, 25


Questions regarding this page should be directed to the primary support astronomer (Yuhei Takagi,

Please note that all numbers on these pages are subject to change as the performance of AO188 is better determined.

Note: Previous AO36 system has been decommissioned since S08B semester and no longer available. If you need the information of AO36, please see old AO page.

Jul 28 2023

© 2000 Subaru Telescope, NAOJ.