Papers by Matthew Britton
TMT M1/M2 Alignment
This report presents an analysis of the effects of M2 misalignment on the field dependent point s... more This report presents an analysis of the effects of M2 misalignment on the field dependent point spread function of the Thirty Meter Telescope. This analysis describes simulations of physical optics wave propagation through the M1/M2 relay and on to a reimaged pupil plane. A simulated Shack Hartmann wavefront sensor is employed in this plane to measure the field dependent wavefront aberrations through the relay. The simulations demonstrate that by driving the M2 out of alignment and observing the character of the resulting field dependent wavefront aberrations, the nature of the M2 misalignment may be identified. In particular, simultaneous tilt and lateral displacement of M2 can result in cancellation of the wavefront aberrations for a point source on the optical axis. Measurement of the wavefront phase aberrations for off axis point sources will eliminate this degeneracy.
Mass-Dimm Setup at Palomar
ABSTRACT We describe the implementation at Palomar Observatory of an automatic, robotic atmospher... more ABSTRACT We describe the implementation at Palomar Observatory of an automatic, robotic atmospheric turbulence monitoring system. The system is based on a 12 inch Meade RCX-400 telescope, coupled with a combined MASS-DIMM unit built at Tololo. The system operates every clear night and stores measurements of the vertical turbulence profile, along with derived turbulence parameters such as seeing, in a database. These values are available in real time to observers. The MASS information has been tested to accurately predict the field dependent point spread function from the Palomar Adaptive Optics System. These predictions have enabled enhanced photometry and astrometry with imaging detectors on the Hale 200-inch telescope. The information has also been used by observers to optimize observing strategies in response to seeing conditions, particularly during Adaptive Optics (AO) and Laser Guide Star (LGS-AO) observing runs.
SLGLAO: An all-sky, wide field adaptive optics system for large aperture telescopes
TMT M1/M2 Alignment
1 Summary This report presents an analysis of the eects of M2 misalignment on the field dependent... more 1 Summary This report presents an analysis of the eects of M2 misalignment on the field dependent point spread function of the Thirty Meter Telescope. This analysis describes simulations of physical optics wave propagation through the M1/M2 relay and on to a reimaged pupil plane. A simulated Shack Hartmann wavefront sensor is employed in this plane to measure the field dependent wavefront aberrations through the relay. The simulations demonstrate that by driving the M2 out of alignment and observing the character of the resulting field dependent wavefront aberrations, the nature of the M2 misalignment may be identified. In particular, simultaneous tilt and lateral displacement of M2 can result in cancellation of the wavefront aberrations for a point source on the optical axis. Measurement of the wavefront phase aberrations for o axis point sources will eliminate this degeneracy. 2 Deliverables • This report This report describes the methodology used in these simulations. The report ...
Mass-Dimm Setup at Palomar
We describe the implementation at Palomar Observatory of an automatic, robotic atmospheric turbul... more We describe the implementation at Palomar Observatory of an automatic, robotic atmospheric turbulence monitoring system. The system is based on a 12 inch Meade RCX-400 telescope, coupled with a combined MASS-DIMM unit built at Tololo. The system operates every clear night and stores measurements of the vertical turbulence profile, along with derived turbulence parameters such as seeing, in a database. These values are available in real time to observers. The MASS information has been tested to accurately predict the field dependent point spread function from the Palomar Adaptive Optics System. These predictions have enabled enhanced photometry and astrometry with imaging detectors on the Hale 200-inch telescope. The information has also been used by observers to optimize observing strategies in response to seeing conditions, particularly during Adaptive Optics (AO) and Laser Guide Star (LGS-AO) observing runs.
MILES: A new concept for wide-field UV/optical spectroscopy for the TMT project
MILES is a 4-shooter multi-slit UV/optical spectrograph concept designed for the Thirty Meter Tel... more MILES is a 4-shooter multi-slit UV/optical spectrograph concept designed for the Thirty Meter Telescope (TMT) project which uses a focal reducer as a fore-optics relay to increase field of view, reduce the size of the multi-slit units and to simplify the spectrograph optics. The system delivers a 75 square arcminute total field of view which is divided into 4 sub-fields
AO Photometry for NGAO
In the remainder of this section we will briefly review astronomical applications that require ph... more In the remainder of this section we will briefly review astronomical applications that require photometric precision or high dynamic range.
Caltech Optical Observatories and its partners are pursuing a vigorous program of laser guide sta... more Caltech Optical Observatories and its partners are pursuing a vigorous program of laser guide star (LGS) adaptive optics on the 5-meter diameter and other telescopes at Palomar Mountain. A full year of commissioning photoreturn results from the University of Chicago sum-frequency sodium laser system is now available. In addition to LGS progress, we have demonstrated diffraction-limited on-sky NGS imaging resolution of 31 milliarcsec (152 nanoradians) using a Cambridge University fast framing, photon counting CCD camera. Leveraging our development of cutting-edge anisoplanatic PSF estimation techniques, based on C n 2 (h,t) monitoring now in routine use at Palomar, we have achieved differential photometric precision well better than 1% and astrometric accuracy better than 1 milliarcsec. These accomplishments hint at the visible light science capabilities we expect to realize via a major facility upgrade planned for Summer 2010. This upgrade, known as PALM-3000, will also incorporate an AMNH-developed speckle-suppression integral field spectrocoronagraph and a JPL-developed nanometerprecision calibration unit to achieve contrast levels of ~10-6 , down to apparent companion magnitude of m V ~ 25 in a 300 second exposure at an angular target offset of 1.0 arcsec in median seeing conditions. For 1-2.5 meter telescopes, we have successfully closed the MEMS DM-based AO loop in the laboratory, demonstrating the basic affordability of compact Rayleigh LGS systems based on our architecture.
International Astronomical Union Colloquium, 2000
Systematic effects currently dominate the timing residuals of the pulsar PSR J0437–4715. These sy... more Systematic effects currently dominate the timing residuals of the pulsar PSR J0437–4715. These systematics arise from transformations that occur during the propagation and detection of radio waves. The transformation properties of polarized radiation are related to the Lorentz group, and such effects may be represented using Lorentz transformations. These effects may be removed using the techniques of polarimetric self-calibration. Alternatively, an invariant profile may be formed from the polarimetric analogue of the Lorentz invariantI2–Q2–U2–V2and used for pulsar timing. Observations of PSR J0437–4715 are presented that show the consistency between these two techniques.
International Astronomical Union Colloquium, 1996
We use radio-wave scattering in the Vela supernova remnant, surrounding the Vela pulsar, as an AU... more We use radio-wave scattering in the Vela supernova remnant, surrounding the Vela pulsar, as an AU-scale lens to study the Vela pulsar’s emission region.
Pulsar Applications of the Caltech Parkes Swinburne Baseband Processing System
International Astronomical Union Colloquium, 2000
The Caltech-Parkes-Swinburne Recorder (CPSR) was installed at the Parkes Radio-telescope in Augus... more The Caltech-Parkes-Swinburne Recorder (CPSR) was installed at the Parkes Radio-telescope in August of 1998. It is capable of continuously two-bit quadrature-sampling a 20 MHz bandpass in two polarizations, though other configurations are possible. Since its successful installation, over 17 Terabytes of observational data have been recorded. These data were processed using the Swinburne Baseband Processing System (SBPS), a suite of data management and reduction software executed using a Beowulf-style cluster of high-performance workstations. A description of CPSR and SBPS is presented herein, followed by a brief presentation of some results from the past year of observations, and an outline of possible future uses of the system.
SPIE Proceedings, 2014
The LSST is an integrated, ground based survey system designed to conduct a decade-long time doma... more 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.
<title>Numerical simulations of single conjugate adaptive optics systems</title>
Advancements in Adaptive Optics, 2004
Arroyo is an open source, cross-platform C++ class library project designed for modeling of elect... more 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 Anisoplanatic Point‐Spread Function in Adaptive Optics
Publications of the Astronomical Society of the Pacific, 2006
Adaptive Optics Systems V, 2016
General relativity can be tested in the strong gravity regime by monitoring stars orbiting the su... more 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.
Nature Communications, 2016
We show here that computer game players can build high-quality crystal structures. Introduction o... more We show here that computer game players can build high-quality crystal structures. Introduction of a new feature into the computer game Foldit allows players to build and real-space refine structures into electron density maps. To assess the usefulness of this feature, we held a crystallographic model-building competition between trained crystallographers, undergraduate students, Foldit players and automatic model-building algorithms. After removal of disordered residues, a team of Foldit players achieved the most accurate structure. Analysing the target protein of the competition, YPL067C, uncovered a new family of histidine triad proteins apparently involved in the prevention of amyloid toxicity. From this study, we conclude that crystallographers can utilize crowdsourcing to interpret electron density information and to produce structure solutions of the highest quality.
Advances in Adaptive Optics II, 2006
We arrive at a Ground Layer Adaptive Optics (GLAO) design that offers true seeing-improved perfor... more 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.
Advancements in Adaptive Optics, 2004
The scientific return on adaptive optics on large telescopes has generated a new vocabulary of di... more 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.
Advances in Adaptive Optics II, 2006
We have built and field tested a multiple guide star tomograph with four Shack-Hartmann wavefront... more 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.
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Papers by Matthew Britton