General relativity can be tested in the strong gravity regime by monitoring stars orbiting the supermassive black hole at the Galactic Center with adaptive optics. However, the limiting source of uncertainty is the spatial PSF variability due to atmospheric anisoplanatism and instrumental aberrations. The Galactic Center Group at UCLA has completed a project developing algorithms to predict PSF variability for Keck AO images. We have created a new software package (AIROPA), based on modified versions of StarFinder and Arroyo, that takes atmospheric turbulence profiles, instrumental aberration maps, and images as inputs and delivers improved photometry and astrometry on crowded fields. This software package will be made publicly available soon.
The LSST is an integrated, ground based survey system designed to conduct a decade-long time domain survey of the
optical sky. It consists of an 8-meter class wide-field telescope, a 3.2 Gpixel camera, and an automated data processing
system. In order to realize the scientific potential of the LSST, its optical system has to provide excellent and consistent
image quality across the entire 3.5 degree Field of View. The purpose of the Active Optics System (AOS) is to optimize
the image quality by controlling the surface figures of the telescope mirrors and maintaining the relative positions of the
optical elements. The basic challenge of the wavefront sensor feedback loop for an LSST type 3-mirror telescope is the
near degeneracy of the influence function linking optical degrees of freedom to the measured wavefront errors. Our
approach to mitigate this problem is modal control, where a limited number of modes (combinations of optical degrees
of freedom) are operated at the sampling rate of the wavefront sensing, while the control bandwidth for the barely
observable modes is significantly lower. The paper presents a control strategy based on linear approximations to the
system, and the verification of this strategy against system requirements by simulations using more complete, non-linear
models for LSST optics and the curvature wavefront sensors.
Anisoplanatism is a primary source of photometric and astrometric error in single-conjugate adaptive optics. We present initial results of a project to model the off-axis optical transfer function in the adaptive optics system at the Keck II telescope. The model currently accounts for the effects of atmospheric anisoplanatism in natural guide star observations. The model for the atmospheric contribution to the anisoplanatic transfer function uses contemporaneous MASS/ DIMM measurements. Here we present the results of a validation campaign using observations of naturally guided visual binary stars under varying conditions, parameterized by the <i>r</i><sub>0</sub> and θ<sub>0</sub> parameters of the C<sup>2</sup><sub>n</sub> atmospheric turbulence profile. We are working to construct a model of the instrumental field-dependent aberrations in the NIRC2 camera using an artificial source in the Nasmyth focal plane. We also discuss our plans to extend the work to laser guide star operation.
W. M. Keck Observatory (WMKO) is currently engaged in the design of a powerful new Adaptive Optics (AO) science
capability providing precision correction in the near-IR, good correction in the visible, and faint object multiplexed
integral field spectroscopy. Improved sensitivity will result from significantly higher Strehl ratios over narrow fields (<
30" diameter) and from lower backgrounds. Quantitative astronomy will benefit from improved PSF stability and
knowledge. Strehl ratios of 15 to 25% are expected at wavelengths as short as 750 nm. A multi-object AO approach
will be taken for the correction of multiple science targets over modest fields of regard (< 2' diameter) and to achieve
high sky coverage using AO compensated near-IR tip/tilt sensing. In this paper we present the conceptual design for this
system including discussion of the requirements, system architecture, key design features, performance predictions and
We have recently demonstrated diffraction-limited resolution imaging in the visible on the 5m Palomar Hale telescope.
The new LAMP instrument is a Lucky Imaging backend camera for the Palomar AO system. Typical resolutions of
35-40 mas with Strehls of 10-20% were achieved at 700nm, and at 500nm the FWHM resolution was as small as 42
milliarcseconds. In this paper we discuss the capabilities and design challenges of such a system used with current and
near future AO systems on a variety of telescopes. In particular, we describe the designs of two planned Lucky Imaging
+ AO instruments: a facility instrument for the Palomar 200" AO system and its PALM3K upgrade, and a visible-light
imager for the CAMERA low-cost LGS AO system planned for the Palomar 60" telescope. We introduce a Monte Carlo
simulation setup that reproduces the observed PSF variability behind an adaptive optics system, and apply it to predict the
performance of 888Cam and CAMERA. CAMERA is predicted to achieve diffraction-limited resolution at wavelengths as
short as 350 nm. In addition to on-axis resolution improvements we discuss the results of frame selection with the aim of
improving other image parameters such as isoplanatic patch sizes, showing that useful improvements in image quality can
be made by Lucky+AO even with very temporally and spatially undersampled data.
Deployed as a multi-user shared facility on the 5.1 meter Hale Telescope at Palomar Observatory, the PALM-3000 highorder
upgrade to the successful Palomar Adaptive Optics System will deliver extreme AO correction in the near-infrared,
and diffraction-limited images down to visible wavelengths, using both natural and sodium laser guide stars. Wavefront
control will be provided by two deformable mirrors, a 3368 active actuator woofer and 349 active actuator tweeter,
controlled at up to 3 kHz using an innovative wavefront processor based on a cluster of 17 graphics processing units. A
Shack-Hartmann wavefront sensor with selectable pupil sampling will provide high-order wavefront sensing, while an
infrared tip/tilt sensor and visible truth wavefront sensor will provide low-order LGS control. Four back-end instruments
are planned at first light: the PHARO near-infrared camera/spectrograph, the SWIFT visible light integral field
spectrograph, Project 1640, a near-infrared coronagraphic integral field spectrograph, and 888Cam, a high-resolution
visible light imager.
CAMERA is an autonomous laser guide star adaptive optics system designed for small aperture telescopes.
This system is intended to be mounted permanently on such a telescope to provide large
amounts of flexibly scheduled observing time, delivering high angular resolution imagery in the visible
and near infrared. The design employs a Shack Hartmann wavefront sensor, a 12x12 actuator MEMS
device for high order wavefront compensation, and a solid state 355nm ND:YAG laser to generate a
guide star. Commercial CCD and InGaAs detectors provide coverage in the visible and near infrared.
CAMERA operates by selecting targets from a queue populated by users and executing these observations
autonomously. This robotic system is targeted towards applications that are diffcult to address
using classical observing strategies: surveys of very large target lists, recurrently scheduled observations,
and rapid response followup of transient objects. This system has been designed and costed, and
a lab testbed has been developed to evaluate key components and validate autonomous operations.
We discuss the limits of ground-based astrometry with adaptive optics based on experiments using the core of
the Galactic globular cluster M5. We have recently achieved ⪅ 100microarcsecond astrometric precision and
accuracy at the Hale 200-inch telescope. Here we apply the same experimental design considerations and optimal
estimation technique to explore the astrometric precision of the Keck II telescope. We find that high-precision
astrometry at ≈ 50 microarcsecond level is possible at Keck in 20 seconds. We discuss the potential of differential
astrometry for current and next generation large aperture telescopes based on these results.
A point source deconvolution technique is described that models the effects of anisoplanatism on the adaptive optics point spread function. This technique is used in the analysis of a quadruple system observed using the Palomar Adaptive Optics system on the Hale 5 meter telescope. Two members of this system reside in a .1 asec double. Deconvolution of this close double was performed using the PSF of a third member of the system, which was offset from the double by 12 asec. Incorporation of anisoplanatism into the deconvolution procedure requires knowledge of the turbulence profile, which was measured at the time of these observations using a DIMM/MASS unit at Palomar Observatory.
PALM-3000 is proposed to be the first visible-light sodium laser guide star astronomical adaptive optics system. Deployed as a multi-user shared facility on the 5.1 meter Hale Telescope at Palomar Mountain, this state-of-the-art upgrade to the successful Palomar Adaptive Optics System will have the unique capability to open the visible light spectrum to diffraction-limited scientific access from the ground, providing angular imaging resolution as fine as 16 milliarcsec with modest sky coverage fraction.
We arrive at a Ground Layer Adaptive Optics (GLAO) design that offers true seeing-improved performance and
operation for the red and infrared wavelengths. The design requires an adaptive secondary (AM2) and that the
sodium Laser Guide Star (LGS) launch telescope be able to steer four of the beams to 8.5 arcminutes off-axis.
When provided with this, the proposed design is potentially the simplest, lowest cost design that can take the
form of an upgrade. This is seen as a significant advantage over designs that would build an adaptive mirror
into each of the four arms of WFOS. We show that the performance penalty for using one mirror instead of four
to correct the entire 81 square arcminute WFOS field is minor.
In this paper, we provide an overview of the adaptive optics (AO) program for the Thirty Meter Telescope (TMT) project, including an update on requirements; the philosophical approach to developing an overall AO system architecture; the recently completed conceptual designs for facility and instrument AO systems; anticipated first light capabilities and upgrade options; and the hardware, software, and controls interfaces with the remainder of the observatory. Supporting work in AO component development, lab and field tests, and simulation and analysis is also discussed. Further detail on all of these subjects may be found in additional papers in this conference.
We have built and field tested a multiple guide star tomograph with four Shack-Hartmann wavefront sensors. We predict the wavefront on the fourth sensor channel estimated using wavefront information from the other three channels using synchronously recorded data. This system helps in the design of wavefront sensors for future extremely large telescopes that will use multi conjugate adaptive optics and multi object adaptive optics. Different wavefront prediction algorithms are being tested with the data obtained. We describe the system, its current capabilities and some preliminary results.
The Thirty Meter Telescope (TMT), the next generation giant segmented mirror telescope, will have unprecedented
astronomical science capability. Since science productivity is greatly enhanced through the use of adaptive optics, the
TMT science team has decided that adaptive optics should be implanted on all the IR instruments. We present the
results of a feasibility study for the adaptive optics systems on the infrared multi-object spectrograph, IRMOS and
report on the design concepts and architectural options. The IRMOS instrument is intended to produce integral field
spectra of up to 20 objects distributed over a 5 arcminute field of regard. The IRMOS adaptive optics design is unique
in that it will use multiple laser guidestars to reconstruct the atmospheric volume tomographically, then apply AO
correction for each science direction independently. Such a scheme is made technically feasible and cost effective
through the use of micro-electromechanical system (MEMS) deformable mirrors.
Adaptive Optics (AO) will be essential for at least seven of the eight science instruments currently planned for the Thirty Meter Telescope (TMT). These instruments include three near infra-red (NIR) imagers and spectrometers with fields of view from 2 to 30 arc seconds, a mid-IR echelle spectrometer, a planet formation imager/spectrometer, a wide field optical spectrograph, and a NIR multi-object spectrometer with multiple integral field units deployable over a 5 arc minute field of regard. In this paper we describe the overall AO reference design that supports these instruments, which consists of a facility AO system feeding the first three instruments and dedicated AO systems for the remaining four. Key design challenges for these systems include very high-order, large-stroke wavefront correction, tip-tilt sensing with faint natural guide stars to maximize sky coverage, laser guidestar wavefront sensing on a very large aperture, and achieving extremely high contrast ratios for the detection of extra-solar planets and other faint companions of bright stars. We describe design concepts for meeting these challenges and summarize our supporting plans for AO component development.
This paper presents a series of studies of single conjugate adaptive
optics systems that use numerical simulation to investigate aspects of
system performance not addressed by traditional statistical metrics.
These studies include investigations of temporal control loop dynamics
and quantitative comparisons of system performance using different
types of reconstructors.
The scientific return on adaptive optics on large telescopes has generated a new vocabulary of different adaptive optics (AO) modalities. Multiobject AO (MOAO), multiconjugate AO (MCAO), ground-layer AO (GLAO), and extreme contrast AO (ExAO) each require complex new extensions in functional requirements beyond the experience gained with systems operational on large telescopes today. Because of this potential for increased complexity, a more formal requirements development process is recommended. We describe a methodology for requirements definition under consideration and summarize the current scientific prioritization of TMT AO capabilities.
Arroyo is an open source, cross-platform C++ class library project
designed for modeling of electromagnetic wave propagation through
atmospheric turbulence and adaptive optics systems. This paper
describes the functionality available in the library and discusses
future plans for this project.
The California Extremely Large Telescope (CELT) project has recently completed a 12-month conceptual design phase that has investigated major technology challenges in a number of Observatory subsystems, including adaptive optics (AO). The goal of this effort was not to adopt one or more specific AO architectures. Rather, it was to investigate the feasibility of adaptive optics correction of a 30-meter diameter telescope and to suggest realistic cost ceilings for various adaptive optics capabilities. We present here the key design issues uncovered during conceptual design and present two non-exclusive "baseline" adaptive optics concepts that are expected to be further developed during the following preliminary design phase. Further analysis, detailed engineering trade studies, and certain laboratory and telescope experiments must be performed, and key component technology prototypes demonstrated, prior to adopting one or more adaptive optics systems architectures for realization.
In this paper we describe the development of a C++ class library for the simulation of adaptive optics systems. This library includes functionality to simulate the propagation of electromagnetic waves through a randomly generated turbulent atmosphere and through an adaptive optical system. It includes support for extended emitters and laser guide stars, and for different types of wavefront sensors and reconstructors. The library also aims to support parallelization of simulations across symmetric multiprocessor and cluster supercomputers.