Adaptive Optics (AO) implementation is underway at the CHARA Array. Beginning in the 2020A semester, all science operations will be conducted using the AO systems. The CHARA adaptive optics program involves two separate AO systems: (1) a deformable mirror and wavefront sensor located at each telescope to provide tiptilt control and fast AO correction to compensate for atmospheric distortions, (2) a deformable mirror and wavefront sensor on each of the beam-reducing tables inside the lab to provide a slow AO correction for non-common path errors in beam transport from the telescope to the delay lines inside the lab.
All wavefront sensors are currently installed in the lab and the telescopes. Small deformable mirrors are installed in the lab for all beams. Deformable mirrors are installed on all telescopes except for E2 and W2. Currently, the telescope tiptilt and labAO loops are locked for all telescopes during observations. The telescope AO loops are locked for S1, S2, E1, and W1. We expect the deformable mirrors for E2 and W2 to be repaired and installed at the telescopes in the near future.
There are three beam splitters that can be used. Each splitter sends a different percentage of visible light to the telescope AO system and into the lab. The choice of AO beam splitter usually depends on the operating wavelength of the beam combiner:
- IR AO beam splitter: sends more of the visible light to the telescope AO system. The IR splitter is the standard for infrared combiners (CLASSIC, CLIMB, MIRC-X).
- VIS AO beam splitter: sends more of the visible light to the lab. The VIS splitter is the standard for visible light combiners (PAVO, VEGA).
- BARE uncoated AO beam splitter: used for engineering purposes or for special target considerations.
The AO Beam Splitters Technical Report describes the splitters in more detail. Please consult with the CHARA staff if you have any questions on whether a non-standard AO beam splitter could be useful for your target priorities.
The CHARA Array Adaptive Optics Program
ten Brummelaar et al., 2019 SPIE 107034
The AO Beam Splitters at the Telescopes
J. Sturmann, 2020, CHARA Technical Report 101