59 research outputs found
The Subaru Coronagraphic Extreme AO project
High contrast coronagraphic imaging is a challenging task for telescopes with
central obscurations and thick spider vanes, such as the Subaru Telescope. Our
group is currently assembling an extreme AO bench designed as an upgrade for
the newly commissionned coronagraphic imager instrument HiCIAO, that addresses
these difficulties. The so-called SCExAO system combines a high performance
PIAA coronagraph to a MEMS-based wavefront control system that will be used in
complement of the Subaru AO188 system. We present and demonstrate good
performance of two key optical components that suppress the spider vanes, the
central obscuration and apodize the beam for high contrast coronagraphy, while
preserving the throughput and the angular resolution.Comment: 4 pages, 2nd Subaru International Conference on Exoplanets and Disks:
Their Formation and Diversity, Keauhou - Hawaii, 9-12 March 200
Coronagraphic Low Order Wave Front Sensor : post-processing sensitivity enhancer for high performance coronagraphs
Detection and characterization of exoplanets by direct imaging requires a
coronagraph designed to deliver high contrast at small angular separation. To
achieve this, an accurate control of low order aberrations, such as pointing
and focus errors, is essential to optimize coronagraphic rejection and avoid
the possible confusion between exoplanet light and coronagraphic leaks in the
science image. Simulations and laboratory prototyping have shown that a
Coronagraphic Low Order Wave-Front Sensor (CLOWFS), using a single defocused
image of a reflective focal plane ring, can be used to control tip-tilt to an
accuracy of 10^{-3} lambda/D. This paper demonstrates that the data acquired by
CLOWFS can also be used in post-processing to calibrate residual coronagraphic
leaks from the science image. Using both the CLOWFS camera and the science
camera in the system, we quantify the accuracy of the method and its ability to
successfully remove light due to low order errors from the science image. We
also report the implementation and performance of the CLOWFS on the Subaru
Coronagraphic Extreme AO (SCExAO) system and its expected on-sky performance.
In the laboratory, with a level of disturbance similar to what is encountered
in a post Adaptive Optics beam, CLOWFS post-processing has achieved speckle
calibration to 1/300 of the raw speckle level. This is about 40 times better
than could be done with an idealized PSF subtraction that does not rely on
CLOWFS.Comment: 10 pages, 7 figures, accepted for publication in PAS
First performance of the gems + gmos system. Part1. Imaging
During the commissioning of the Gemini MCAO System (GeMS), we had the
opportunity to obtain data with the Gemini Multi-Object Spectrograph (GMOS),
the most utilised instrument at Gemini South Observatory, in March and May
2012. Several globular clusters were observed in imaging mode that allowed us
to study the performance of this new and untested combination. GMOS is a
visible instrument, hence pushing MCAO toward the visible.We report here on the
results with the GMOS instruments, derive photometric performance in term of
Full Width Half Maximum (FWHM) and throughput. In most of the cases, we
obtained an improvement factor of at least 2 against the natural seeing. This
result also depends on the Natural Guide Star constellation selected for the
observations and we then study the impact of the guide star selection on the
FWHM performance.We also derive a first astrometric analysis showing that the
GeMS+GMOS system provide an absolute astrometric precision better than 8mas and
a relative astrometric precision lower than 50 mas.Comment: 13 pages, 11 figures, accepted for publication in MNRAS on March 23rd
201
SCExAO as a precursor to an ELT exoplanet direct imaging instrument
The Subaru Coronagraphic Extreme AO (SCExAO) instrument consists of a high
performance Phase Induced Amplitude Apodisation (PIAA) coronagraph combined
with an extreme Adaptive Optics (AO) system operating in the near-infrared (H
band). The extreme AO system driven by the 2000 element deformable mirror will
allow for Strehl ratios >90% to be achieved in the H-band when it goes closed
loop. This makes the SCExAO instrument a powerful platform for high contrast
imaging down to angular separations of the order of 1lambda/D and an ideal
testbed for exploring coronagraphic techniques for ELTs. In this paper we
report on the recent progress in regards to the development of the instrument,
which includes the addition of a visible bench that makes use of the light at
shorter wavelengths not currently utilized by SCExAO and closing the loop on
the tip/tilt wavefront sensor. We will also discuss several exciting guest
instruments which will expand the capabilities of SCExAO over the next few
years; namely CHARIS which is a integral field spectrograph as well as
VAMPIRES, a visible aperture masking experiment based on polarimetric analysis
of circumstellar disks. In addition we will elucidate the unique role extreme
AO systems will play in enabling high precision radial velocity spectroscopy
for the detection of small companions.Comment: 7 pages, 2 figures Proceedings of AO4ELTs3 conference, paper 13396,
Florence, Italy, May 201
The subaru coronagraphic extreme AO (SCExAO) system: Wavefront control and detection of exoplanets with coherent light modulation in the focal plane
The Subaru Coronagraphic Extreme-AO (SCExAO) system is designed for high contrast coronagraphic imaging at small angular separations, and is scheduled to see first light on the Subam Telescope in early 2011. The wavefront control architecture for SCExAO is optimized for scattered light control and calibration at small angular separations, and is described in this paper. Key subsystems for the SCExAO wavefront control architecture have been successfully demonstrated, and we report results from these tests and discuss their role in the SCExAO system. Among these subsystems, a technique which can calibrate and remove static and slow speckles which traditionally limit high contrast detections is discussed. A visible light lab prototype system at Subam Telescope recently demonstrated speckle halo reduction to 2e-7 contrast within 2 2λ/D, and removal of static coherent speckles to 3e-9 contrast
The Subaru Coronographic Extreme AO (SCExAO) system: Implementation and performances of the Coronographic Low Order WaveFront Sensor
The Subaru Coronagraphic Extreme AO project (SCExAO) is a high performance coronagraph designed to deliver high contrast at small angular separation. For the detection of structures near the diffraction limit, an accurate control of low order wavefront aberrations - tip-tilt and focus - is essential as these aberrations create light leaks that are the source of confusion in the final science image. To address this major difficulty, we have equipped SCExAO with a specially designed Coronagraphic Low Order WaveFront Sensor (CLOWFS) using defocused images of a reflective ring located in the focal plane, that can track tip-tilt errors as small as 10-3?/D. CLOWFS was originally designed to drive actuators in a closed-loop. Here, we show that it can also be used in post-processing to efficiently subtract the tip-tilt induced coronagraphic leaks in the final science image
Gemini multi-conjugate adaptive optics system review II: Commissioning, operation and overall performance
The Gemini Multi-conjugate Adaptive Optics System - GeMS, a facility
instrument mounted on the Gemini South telescope, delivers a uniform, near
diffraction limited images at near infrared wavelengths (0.95 microns- 2.5
microns) over a field of view of 120 arc seconds. GeMS is the first sodium
layer based multi laser guide star adaptive optics system used in astronomy. It
uses five laser guide stars distributed on a 60 arc seconds square
constellation to measure for atmospheric distortions and two deformable mirrors
to compensate for it. In this paper, the second devoted to describe the GeMS
project, we present the commissioning, overall performance and operational
scheme of GeMS. Performance of each sub-system is derived from the
commissioning results. The typical image quality, expressed in full with half
maximum, Strehl ratios and variations over the field delivered by the system
are then described. A discussion of the main contributor to performance
limitation is carried-out. Finally, overheads and future system upgrades are
described.Comment: 20 pages, 11 figures, accepted for publication in MNRA
The Subaru coronagraphic extreme AO (SCExAO) system: Visible imaging mode
The Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system is an instrument designed to be inserted between the Subaru AO188 system and the infrared HiCIAO camera in order to greatly improve the contrast in the very close (less than 0.5") neighbourhood of stars. Next to the infrared coronagraphic path, a visible scientific path, based on a EMCCD camera, has been implemented. Benefiting from both Adaptive Optics (AO) correction and new data processing techniques, it is a powerful tool for high angular resolution imaging and opens numerous new science opportunities. We propose here a new image processing algorithm, based on the selection of the best signal for each spatial frequency. A factor 2 to 3 in Strehl ratio is obtained compared to the AO long exposure time depending on the image processing algorithm used and the seeing conditions. The system is able to deliver diffraction limited images at 650 nm (17 mas FWHM).We also demonstrate that this approach offers significantly better results than the classical select, shift and add approach (lucky imaging)
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