CfAO Theme 2 - Adaptive Optics for the Extremely Large Telescopes - Projects for CfAO Year 8 (FY2007)

The highest recommendation of the National Academy of Sciences’ Astronomy and Astrophysics Survey Report for ground-based astronomy was the design and construction of a 30-m telescope equipped with adaptive optics. Developing an adaptive optics system for such a telescope is extremely challenging and requires an extension of almost every aspect of AO system design and component technology. The CfAO objective in this Theme for the second five years of the Center is to make a major contribution towards achieving this national priority, especially in areas where cross-institutional and multidisciplinary collaboration is required.

Link to the Year 7 Annual Report to NSF

Goals of Theme 2: Prior to CfAO year 7, the main technical emphasis of Theme 2 was to develop feasible point designs for AO systems for the extremely large telescopes and to develop the modeling and analysis tools for multi-guidestar tomography and multi-conjugate adaptive optics. Having largely accomplished this (with the kickoff of system designs for the TMT, GSMT, and Keck Next Generation AO projects benefiting from this work), beginning in CfAO year 7, we changed the emphasis of the technical part of Theme 2 to focus on CfAO "legacy projects." There are two AO technology areas in which CfAO is making a major impact: MEMS deformable mirrors and pulsed sodium lasers. By focusing on these promising technical areas we hope establish the legacy of the CfAO as a developer of new AO component technologies. Theme 2 also continues to support work in research astronomy using existing AO systems and the development of quantitative methods of analyzing AO data.

Here is a summary of this year's funded research projects:

Astronomy with AO

• CfAO Treasury Survey (CATS) - Claire Max, UCSC, David Koo, UCSC, James Larkin, UCLA, Matthew Britton, Caltech
• Galactic Center Science with AO - Andrea Ghez, UCLA
• Imaging of Solar System Bodies - Imke de Pater, UC Berkeley

MEMS

• MEMS Consortium - Donald Gavel, UCSC
• 3-Dimensional MEMS for Adaptive Optics - Joel Kubby, UCSC
• Through Wafer Interconnects for MEMS DMs - Steven Cornelison, Boston Micromachines Corporation

Guide Star Laser Development

• Advanced Guide Star Laser Technology Development - Deanna Pennington, LLNL
• Development Laser for Palomar AO System - Ed Kibblewhite, U. Chicago (at Palomar Observatory)

Quantitative Astronomy and other Analysis Projects

• Predictive Control Algorithms - Donald Wiberg, UCSC
• System Level Modeling and Optimization of the Polar Coordinate Detector Combined with Modeling and Simulation of algorithms for Wavefront Sensing with Elongated Sodium Laser Guide Stars - Donald Gavel, UCSC, Sean Adkins, Keck Observatory, Luc Gilles, TMT

Abstracts

CfAO Treasury Survey (CATS) - Claire Max, UCSC, David Koo, UCSC, James Larkin, UCLA, Matthew Britton, Caltech

Abstract: We are developing the CfAO Treasury Survey (called CATS). CATS is using adaptive optics to observe a large, deep sample of galaxies in the early Universe. The goal of this legacy scientific program is to track the assembly of galaxies like our own Milky Way, to characterize its history of star formation, to study black holes in the cores of active galaxies, and to characterize mergers between galaxies in the early universe. The near-infrared adaptive optics (AO) observations are up to 4 times sharper than those obtained by the Hubble Space Telescope. The adaptive optics data will achieve high visibility in the broad astronomical community because the chosen sky fields all have complementary observations at other wavelengths, using space-based images from far infrared, optical to x-ray wavelengths, and ground-based images at radio and sub-mm wavelengths. We will make our AO data available to the public in an on-line archive.

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Galactic Center Science with AO - Andrea Ghez, UCLA

Abstract: This program focuses on the use of Adaptive Optics to study the center of our Galaxy from a technical, educational, and astronomical point of view.

• Technically, the Galactic Center presents many challenges which range from observational, due to the lack of a bright natural guide star at optical wavelengths, to analytical, due to the crowded stellar field at near-infrared wavelengths. We therefore propose to study the Adap- tive Optics performance on this field with a variety of different systems (Keck vs. Gemini; NGS vs. LGS) from the point of view of PSF qualiity (overall Strehl), stability and anisoplanitism. In addition we will investigate the astrometric and spectroscopic accuracies that can be achieved in such a crowded stellar field. These results will be applicable to a number of di®erent studies and are thus of large interest to the general CfAO community.
• Educationally, this program offers tremendous opportunities to both display the power of AO and to educate the general community. The benefits of AO are very visually demonstrable and the subject of supermassive black holes is of great interest to the public. Since much of the astronomical investigation rests on very basic principles of physics, it also has served as a great vehicle for more generally educating the public through public lectures, documentaries, and text books. We propose to continue these outreach activities.
• Astronomically, we propose to study the environment of the Galaxy's central supermassive black hole to measure the dynamics, distribution, and properties of the stars in the central stellar cluster. The proposed spectroscopy and imaging will allow us to obtain the most accurate and precise estimate of the distance to the Galactic Center, constrain the dark mass distribution at smaller radii than ever before (with special focus now on what might surround the central black hole), improve studies of counterparts to Sgr A* at near-infrared wavelengths, and resolve the paradox of apparently young stars in an environment that is currently quite hostile to star formation, given the strong tidal forces presented by the black hole and the low gas densities. This program serves as an excellent example to the astronomical community of the power of LGS-AO.

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Imaging of Solar System Bodies - Imke de Pater, UC Berkeley

Abstract: AO systems provide a fantastic tool to image planetary objects at a spatial resolution comparable to data obtained by spacecraft, and a spectral resolution superior to infrared spectrometers flown on any spacecraft (e.g., Cassini). In contrast to spacecraft measurements, groundbased observations allow a long term survey on targets which are known for their variability, either through changes in viewing geometry (e.g., planetary rings, binary asteroids and transneptunian objects) or intrinsic to the object itself (e.g. planetary atmospheres, comet activity, volcanoes). Over the past years, we acquired data with several of the currently available AO systems on Keck, the VLT, Gemini, and Lick, using different observing modes (imaging, spectroscopy, LGS imaging, and integral-field spectroscopy) on Titan, Neptune, Uranus, Io, comets, binary asteroids and transneptunian objects (TNO), accomplishing part of our Year 5-7 Milestones. We propose to continue our study of Solar System bodies, while pushing AO techniques to the limits of their capability. Our main emphasis will be on using the integral-field spectrometer OSIRIS at Keck and SINFONI on the VLT, both with and without LGS. We will, for example, observe binary asteroids, TNOs, Io both in and out of eclipse, Titan, and the recently announced Red Spot Jr on Jupiter. We will continue to develop analysis tools (such as radiative transfer codes) with which to analyze spatially resolved spectroscopic data. These tools will be made available to the community at large. Finally, to improve the quality of the data and to extract science (photometry) from our observations, the data need to be deconvolved: this requires extensive testing, and presumably updating, of the recently developed deconvolution package, AIDA, together with PSF characterization.

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MEMS Consortium - Donald Gavel, UCSC

Abstract: We propose that CfAO join a consortium of users to fabricate a MEMS deformable mirror that can be used on 30-meter class telescopes and on extreme adaptive optics systems on 8-10 meter class telescopes. The consortium consists of the Thirty Meter Telescope project (UC, Caltech, AURA, and CNRC partnership), the UCO/Lick Observatory Laboratory for Adaptive Optics, and the Gemini Observatory. (Note: the CfAO contributed to the consortium in Year 7. Consortium efforts continue during year 8.)

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3-Dimensional MEMS for Adaptive Optics - Joel Kubby, UCSC

Abstract: (needed)

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Through Wafer Interconnects for MEMS DMs - Steven Cornelison, Boston Micromachines Corporation

Abstract: High resolution MEMS deformable mirrors are currently limited by the electrical interconnection scheme which requires individual wirebonds for each element in the array. In order to meet the future needs for adaptive optics application for extremely large telescopes, a scaleable electrical interconnect architecture is required to extend the number of actuators from 4000 to more than 10,000. The fabrication of MEMS actuator arrays with through-wafer electrical interconnects is the goal of the proposed project.

The proposed work will use commercially available fabrication processes from two different foundries to achieve the stated goal. Silicon wafers, pre-processed to contain through-wafer interconnections at specified locations, will be used as the substrates for the actuator arrays. These will be fabricated atop the electrical interconnects to demonstrate their functionality and compatibility with the proven deformable mirror production processes. Successful completion of the proposed work will lead the way to economical high actuator count deformable mirrors with a minimal optical footprint which will enable new instruments for astronomical adaptive optics.

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Advanced Guide Star Laser Technology Development - Deanna Pennington, LLNL

Abstract: Laser guide stars (LGS) are crucial to the broad use of adaptive optics (AO), because they facilitate access to a large fraction of possible locations on the sky. Lasers can be tuned to the 589 nm resonance line of atomic sodium to create an artificial beacon at altitudes of 95-105 km, thus coming as close as possible to reproducing the light path of starlight. To realize the full potential of adaptive optics on extremely large telescopes (ELTs), however, new laser and beam projection concepts must be developed with performance characteristics well beyond the current generation of systems. These innovations are needed to defeat the guide star elongation problem induced by the depth of the sodium layer, and to mitigate fratricide of multiple laser signals. Approaches proposed to date include significantly higher-power laser systems, innovative pulse formats, and/or a multiplicity of launch telescopes for each guide star location, none of which have been fully demonstrated at the required performance levels.

We are developing a versatile laser technology based on laser diode-pumped fiber lasers which are sum-frequency mixed in periodically poled materials to provide 589 nm light for LGSAO. This technology will provide a compact, efficient, robust, turnkey laser source required for the multiple beacon AO systems proposed for ELTs. Our goal is to produce a 5-10 W fiber laser system at 589 nm. To date we have demonstrated our prototype fiber laser functions at 2.7 W in continuous wave (CW) mode, suitable for a single LGS on a 3 - 10 m telescope, and at 3.5 W in a pulsed format for mitigation of spot elongation with support from the Adaptive Optics Development Program (AODP). In Y7 we dovetailed the CfAO and AODP programs, focusing on a 10 W pulsed laser as this best supports both our technical goals and the new priorities for Theme 2 established in Y6.

Next generation laser systems must also be sufficiently reliable to enable routine operation in remote, somewhat hostile, observatory environments. Prototyping and experience are needed for low-cost, reliable, properly qualified laser systems, laser beam handling and launch. As our technologies mature, we will field-harden and engineer the components, enabling a field-hardened, automated prototype for deployment on a suitable telescope. We are partnering with UCO Lick staff to develop a proposal for deployment of our laser at Lick Observatory in a visible LGSAO demonstration in Years 8/9. Our technology is also key for all upgrade paths proposed for the 30-m telescope project, which may provide a source of follow-on funding.

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Development of Laser for Palomar AO System - Ed Kibblewhite, U. Chicago (at Palomar Observatory)

Abstract: (needs input) This project funds continued integration and testing of the laser guide star system at Palomar Observatory.

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Predictive Control Algorithms - Donald Wiberg, UCSC

Abstract: The feedback control system of adaptive optics presently does not account for wind blowing the turbulent air in the path of light collected by a telescope. This motion can be seen by the human eye and therefore detected by the control computer. Improving the AO control algorithm to incorporate known wind motion has been shown in simulation to improve seeing (Strehl) by 25% on average. We plan to formulate, simulate, and test several method of estimating bulk wind velocity and incorporate this knowledge into the AO control computer. In years 9 and 10, this idea will be applied to spatially discretized volumes of air turbulence in the light path.

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System Level Modeling and Optimization of the Polar Coordinate Detector Combined with Modeling and Simulation of algorithms for Wavefront Sensing with Elongated Sodium Laser Guide Stars - Donald Gavel, UCSC, Sean Adkins, Keck Observatory, Luc Gilles, TMT

Abstract: This is a collaborative project designed to produce a wavefront sensor that is optimized for laser guide stars. There are two components: 1) specifying the parameters of a new wavefront sensor CCD specifically designed for extended laser guide stars, and 2) developing and analyzing optimal algorithms for laser guide wavefront sensing, with predictions anchored against experimental results at the W.M Keck Observatory and at the UCSC Laboratory for Adaptive Optics.