Subaru Ground Layer AO Science Workshop, Jun. 2013

Baseline Specifications and Questions to Speakers


Baseline Specifications of GLAO

GLAO (Ground-Layer Adaptive Optics) will achieve seeing improvement over the entire φ > 10 arcmin field of view (FoV) by correcting only for the disruption of wavefront caused by the ground layer of the Earth’s atmosphere. Although the Strehl ratio achievable with GLAO should be less than those by some AO systems (such as classical single-conjugate AO (like Subaru / AO188)) which provide diffraction limited images in some specific area of the sky, GLAO can correct images over much wider FoV compared to the existing AO systems.

The following baseline specifications of GLAO are based on numerical simulations by S. Oya (Subaru telescope) et al. in 2011.

The simulations have been updated and there's a summary:

Please refer this PDF to see the dependency on observation conditions (such as elevation, seasonal variations etc.).


Baseline Specifications of Instrument(s)

With GLAO we expect almost uniform seeing improvement for FoV over φ > 10 arcmin. MOIRCS, the current NIR imaging and multi-object spectrograph for Subaru Telescope, has FoV of 4' x 7'. In order to fully utilize the capability of GLAO, we definitely need to develop new wide-field instruments. We started optical design studies of the new wide-field NIR instrument for the Cassegrain focus of Subaru Telescope to assess its feasibility.

We found that there is a possible design with a 13' diameter FoV for the case with the same optical design parameters of the secondary mirror as those of the current infrared secondary mirror. It was also found that if we change the optical parameters of the primary and secondary mirrors, we will be able to achieve a ∼ 16' diameter FoV. The FoV can be even bigger if we split the FoV. We also studied restrictions to achieve wider FoV using the Cassegrain focus from the Subaru telescope structure which was originally designed to achieve FoV ∼ 6' diameter. We have identified there are structures which cause significant vignetting if the beam is > 14 arcmin diameter even if we remove some components in the Cassegrain focus such as ADC and AG/SH.

On the other hand, it is very challenging to build wide-field NIR instruments. For instance, optical components with high throughput in NIR are very fragile and have size limitations. We need to cool components to suppress thermal emission. The NIR detectors are much more expensive than optical CCDs.

In order to construct a feasible development plan, we need to define what are the minimum requirements for the instrument from the scientific point of view. We would like to ask speakers and participants what kind of capabilities are really essential for your science cases.

Below is the baseline specifications of the instruments.


Questions to Speakers

To all workshop speakers: please include your responses to the questions below (especially to the five primary questions).

Questions on instrument specifications

Primary questions

Auxiliary questions

Questions on legacy science


References


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