AO188

Information for applicants

Only NGS mode available with AO188 in S21A:

The laser is still under the upgrading process. Therefore only NGS mode is available in S21A. Please make sure your science does not require the use of LGS. If the laser upgrade is completed in the middle of S21A, we will notify the observers whose proposals have been accepted for S21A, and they can choose to use the new laser under the risk share condition. However, again, only NGS science in your proposal will be reviewed.

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

  • Those who want to observe with non-sidereal objects using the atmosperic dispersion corrector

Introduction

Note: Please read Planning Observations carefully before submitting proposals.

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, and IRD 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 has been open to public since the latter half of S11A semester with the brightness of the LGS around 10.5 mag in R-band in 2011; however, it became R=14 at El=80 degree with a natural seeing of 0.5 arcsec as of January 2019. Figures below show the on-sky brightness of the LGS measured in 2011 and 2019. Because such faint LGS is not sufficient for AO correction, we decomissioned the laser in July 2019 and are currently working on a new LGS facility. Please check LGS upgrade status page for the most updated information.

Laser brightness as a function of elevation. The laser brightness is presented as a detector count on the left figure and R magnitude on the right figure.

AO fits header information can be found here.

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.

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

Contacts

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

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

29 July 2020



© 2020 Subaru Telescope, NAOJ.