|Target acquisition and Image quality|
|Strehl Ratio, FWHM||See AO188 performance|| SCExAO phase I provides no significant
improvement in image quality over AO188
| Target Acquisition and
|AO188 target acquisition time + 10 mn||Does not include fine tuning of speckle control loop|
|Seeing limit||~1.2"||See AO188 performance|
|Faint limit||R=8, H=5||Performance improves steeply with brighter targets|
|Bright limit||N/A|| Neutral Density filters can be placed in front of wavefront
sensor and HiCIAO when observing bright targets
|Detector||Hawaii 2RG||See HiCIAO instrument description|
|Wavelength coverage||See HiCIAO instrument description||SCExAO feeds HiCIAO with wavelengths longer than 950nm|
|Field-of-view, plate scale||nominal HiCIAO values||SCExAO preserves HiCIAO's plate scale and FOV|
|SCExAO throughput to HiCIAO||35 %|| Assumes 50%/50% beam splitter between HiCIAO and
SCExAO science camera, does not include PIAA lenses
|Coronagraph modes|| PIAA, Vortex, 4QPM,
|Angular Differential Imaging||YES||SCExAO operates in fixed pupil mode|
|Active Speckle control||YES|| Speckle control performed using SCExAO
internal science camera
|Tip-Tilt control||YES|| Tip-Tilt control performed using SCExAO
Low Order Wavefront Sensor
|Spectral Differential Imaging||NO||Will be offered at a later time|
|Polarimetric imaging||NO||Will be offered at a later time|
|Cameras: Internal SCExAO science camera|
|Detector||InGaAs, 320x256||Axiom Optics OWL SW1.7HS|
|Wavelength coverage||J, H band||0.9-1.7 μm|
|Field-of-View||3.4"x 2.7"||10.76 mas/pixel|
|Frame rate||346 Hz max||adjustable|
|Readout Noise||115 e-|
|Phase I High Contrast Imaging Performance|
|Inner Working Angle||1 to 3 l/D||Function of coronagraph configuration|
|PIAA Coronagraph optics throughput||52%|
| Detection contrast threshold:
1-4 λ/D (40-160 mas)
|1e-4|| H band, Approximate value, assumes bright star
and PSF post-calibration
| Detection contrast threshold:
4-20 λ/D (160-800 mas)
|1e-5|| H band, Approximate value, assumes bright star
and PSF post-calibration
|Phase II High Order Wavefront Correction|
|Extreme AO|| HOWFS development is progressing well and we should
be able to offer additional wavefront correction on top of
AO188 in S14B. However, at this point we can not commit to a Strehl ratio.
|Coronagraph type||PIAA||Vortex||4QPM||Shaped pupil|
|Inner working angle (λ/D)||1.5||1||1||3|
Speckle nulling is performed with the camera used for high frame rate imaging. This camera is the same as the one used for the LOWFS. They are both Axiom Optics OWL SW1.7HS units, which have an InGaAs CMOS array with 320x256 pixels that are 30x30 μm in size. These cameras can run full frame at 346 Hz and have a read noise of 115 and 140 e- respectively. The dark current is such that the maximum exposure is ~5-10 s. Please note that the speckle nulling routine operates on the speckles which are ~1000 x fainter than the central PSF and hence this must be taken into consideration when selecting your target, in light of the noise characteristics. The high frame rate/speckle nulling camera has a plate scale of 10.76 mas/pixel and a maximum field-of-view of 3.4"x 2.7". Please refer to the HiCIAO page for information on that camera. The plate scale of HiCIAO when used in conjunction with SCExAO is preserved. The high frame rate/speckle nulling camera can be used with a series of bandpass filters which include: y-band, J-band, H-band and 50 nm bandwidth centered at 1650 nm.
(Left) High frame rate science camera/speckle nulling camera. Mounted on a long translation stage to move between
the focal and pupil planes. (Middle) LOWFS camera. (Right) HiCIAO camera.
The internal calibration source consists of a Fianium super continuum source and 2 laser diodes centered at 650 and 1550 nm. The light from the source is delivered via an endlessely single-mode fiber to the bench ensuring a diffraction-limited calibration PSF from the visible to K-band. The brightness and spectral bands of the injected light can be easily controlled. In addition there is a turbulence simulator that can be used for realistic simulations of on-sky performance in the laboratory.
(Left) Internal calibration source unit (a.k.a rainbow maker). (Middle) Super continuum laser source attached to source box. (Right) Internals of
calibration source box. There is a shutter to turn the light on/off, and three wheels to control the ND in the vis/IR and spectral content.
The April observing run was a great success. We revalidated speckle nulling and the LOWFS on-sky with convincing results and VAMPIRES collected a ton of data following its upgrades as well. The icing on the cake was the demonstration of closed loop operation of the high order wavefront sensor (non-modulated pyramid wavefront sensor). With the implementation of 5 GPU's since the December run, we managed to drive the PyWFS at 800 Hz on 200 modes on-sky. We tested the loops performance to cancel aberrations by adding varying static wavefront errors via our deformable mirror on top of the pre-existing aberrations and then watched the restoration of the PSF and the applied volt map post correction. Next steps include adding regularization to prevent actuators in and around the pupil edges from saturating, eliminating existing delays in the loop and applying off-sky response matrices to attempt to get extreme AO correction on the coming June run. Stay tuned! In addition we observed significant improvements in PSF stability as a result of the HiCIAO vibration isolation upgrades. Great success!
The HiCIAO camera was overhauled to include a dual bellows vibration isolation unit. More information can be found on the vibrations page.
(Left) The new dual bellows vibration isolation system installed on HiCIAO.
We received funding to purchase two state-of-the-art cameras, namely OCAM 2K and MKIDS. OCAM 2K (FirstLight) is one of the most advanced visible cameras (frame rate of 3.7 kHz with binning, 0.3e- read noise, <0.01e- dark current and very high quantum efficiency between 500 and 900 nm). This camera will be used to replace the Andor Zyla currently used for the non-modulated pyramid wavefront sensor and boost performance significantly. This camera is expected to be delivered in late May 2014 and installed and running a few months after this date. MKIDS stands for Microwave Kinetic Inductance Detector and is a photon counting, energy discriminating superconducting based technology. It is being developed by Prof. Ben Mazin's group at UC Santa Barabara and we are fortunate enough to work with them developing a specific unit for SCExAO. This camera will replace the current high frame rate/speckle nulling camera. With the boost in sensitivity and speed, we will be able to do fast wavefront control and calibration and push speckle nulling and even focal plane wavefront sensing to the limit. MKIDS will take several years to build and test.
(Left) OCAM 2k (Image taken by FirstLight Advanced Imaging). (Middle) MKIDS detector.
(Right) Prof. Ben Mazin with the entire MKIDS camera assembly (Images taken by Mazin's group at UCSB).