Kalman Filter Estimation for Focal Plane Wavefront Correction

Space-based coronagraphs for future earth-like planet detection will require focal plane wavefront control techniques to achieve the necessary contrast levels. These correction algorithms are iterative and the control methods require an estimate of the electric field at the science camera, which requires nearly all of the images taken for the correction. We demonstrate a Kalman filter estimator that uses prior knowledge to create the estimate of the electric field, dramatically reducing the number of exposures required to estimate the image plane electric field. In addition to a significant reduction in exposures, we discuss the relative merit of this algorithm to other estimation schemes, particularly in regard to estimate error and covariance. As part of the reduction in exposures we also discuss a novel approach to generating the diversity required for estimating the field in the image plane. This uses the stroke minimization control algorithm to choose the probe shapes on the deformable mirrors, adding a degree of optimality to the problem and once again reducing the total number of exposures required for correction. Choosing probe shapes has been largely unexplored up to this point and is critical to producing a well posed set of measurements for the estimate. Ultimately the filter will lead to an adaptive algorithm which can estimate physical parameters in the laboratory and optimize estimation.Comment: 14 pages, 9 figures, SPIE Astronomical Telescopes and Instrumentation 2012 conference proceedings. Journal version at arXiv:1301.382

Cueing animations: Dynamic signaling aids information extraction and comprehension

The effectiveness of animations containing two novel forms of animation cueing that target relations between event units rather than individual entities was compared with that of animations containing conventional entity-based cueing or no cues. These relational event unit cues (progressive path and local coordinated cues) were specifically designed to support key learning processes posited by the Animation Processing Model (Lowe & Boucheix, 2008). Four groups of undergraduates (N = 84) studied a user-controllable animation of a piano mechanism and then were assessed for mental model quality (via a written comprehension test) and knowledge of the mechanism's dynamics (via a novel non-verbal manipulation test). Time-locked eye tracking was used to characterize participants' obedience to cues (initial engagement versus ongoing loyalty) across the learning period. For both output measures, participants in the two relational event unit cueing conditions were superior to those in the entity-based and uncued conditions. Time-locked eye tracking analysis of cue obedience revealed that initial cue engagement did not guarantee ongoing cue loyalty. The findings suggest that the Animation Processing Model provides a principled basis for designing more effective animation support

A Framework for the Coordination of Legged Robot Gaits

This paper introduces a framework for representing, generating, and then tuning gaits of legged robots. We introduce a convenient parametrization of gait generators as dynamical systems possessing designer specified stable limit cycles over an appropriate torus. This parametrization affords a continuous selection of operation within a coordination design plane, inspired by biology, spanned by axes that determine the mix of feedforward/feedback and centralized/decentralized control. Tuning the gait generator parameters through repeated physical experiments with our robot hexapod, RHex, determines the appropriate operating point - the mix of feedback and degree of control decentralization - to achieve significantly increased performance relative to the centralized feedforward operating point that has governed its previous behavior. The present preliminary experiments with these new gaits suggest that they may permit for the first time locomotion over extremely rough terrain that is almost as reliable, rapid, and energy efficient as the very fastest or most efficient outcomes centralized feedforward gaits can achieve on level ground

Gait Generation and Optimization for Legged Robots

This paper presents a general framework for representing and generating gaitsfor legged robots. We introduce a convenient parametrization of gait generators as dynamical systems possessing specified stable limit cycles over an appropriate torus. Inspired by biology, this parametrization affords a continuous selection of operation within a coordination design plane spanned by axes that determine the mix of ”feedforward/feedback” and centralized/decentralized” control. Applying optimization to the parameterized gait generation system allowed RHex, our robotic hexapod, to learn new gaits demonstrating significant performance increases. For example, RHex can now run at 2.4m/s (up from 0.8m/s), run with a specific resistance of 0.6 (down from 2.0), climb 45◦ inclines (up from 25◦), and traverse 35◦ inclines (up from 15◦)

Synergies of Subaru and CGI

Given the limited observing time and demanding scenarios of the WFIRST coronagraph instrument (CGI), it is critical to consider how Subaru observations can benefit its observing program. Subaru telescope has a suite of instruments with their adaptive optics (AO) and extreme adaptive optics modules (SCExAO). With SCExAO, the Subaru telescope is capable of detection and spectral characterization of binaries and bright (greater than 5(exp -6) contrast) companions in the near-infrared. This will enable the vetting of targets, disk detection and characterization, and potentially some additional science should CGI identify interesting targets during its technology demonstration and potential guest observer program. Additionally, large companions that are within the inner working angle of the coronagraph can be identified using the VAMPIRES aperture masking interferometer. With highly complementary target brightness and significantly overlapping fields of view, there is a great deal of potential for combined observations with Subaru and CGI. This will represent the first time single observations spanning the visible to near-infrared will be possible for high contrast imaging. We will discuss the overlap of instrumentation over time, the implication of instrument evolution as TMT comes online, and how this can be used to improve both science and technology demonstrations for CGI

Commissioning and performance results of the WFIRST/PISCES integral field spectrograph

The Prototype Imaging Spectrograph for Coronagraphic Exoplanet Studies (PISCES) is a high contrast integral field spectrograph (IFS) whose design was driven by WFIRST coronagraph instrument requirements. We present commissioning and operational results using PISCES as a camera on the High Contrast Imaging Testbed at JPL. PISCES has demonstrated ability to achieve high contrast spectral retrieval with flight-like data reduction and analysis techniques.Comment: Author's copy - Proceedings of SPIE Volume 10400. Citation to SPIE proceedings volume will be added when availabl

Automated Gait Adaptation for Legged Robots

Gait parameter adaptation on a physical robot is an error-prone, tedious and time-consuming process. In this paper we present a system for gait adaptation in our RHex series of hexapedal robots that renders this arduous process nearly autonomous. The robot adapts its gait parameters by recourse to a modified version of Nelder-Mead descent while managing its self-experiments and measuring the outcome by visual servoing within a partially engineered environment. The resulting performance gains extend considerably beyond what we have managed with hand tuning. For example, the hest hand tuned alternating tripod gaits never exceeded 0.8 m/s nor achieved specific resistance helow 2.0. In contrast, Nelder-Mead based tuning has yielded alternating tripod gaits at 2.7 m/s (well over 5 body lengths per second) and reduced specific resistance to 0.6 while requiring little human intervention at low and moderate speeds. Comparable gains have been achieved on the much larger ruggedized version of this machine

Ursinus College Alumni Journal, Spring 1948

Give the steward a break! • President\u27s page • College has full extra-curricular program: Dr. Miller forum speaker; Religious Emphasis Week; Ray Eberle for junior prom • Mrs. Smith resigns alumni secretaryship • College is recipient of paintings and furniture • Congratulations, alumni basketeers! • Women\u27s Club entertains Ursinus senior girls • New associate professor joins college faculty • Nineteen alumni attain doctorates • Still room for students in certain categories • College librarian resigns • A successful season was had by all: Men\u27s basketball; Girls\u27 basketball; Wrestling; Swimming • News about ourselves • Cost of living increase voted faculty members • News around town • Ursinus curriculum undergoes revision • Women\u27s rules liberalizedhttps://digitalcommons.ursinus.edu/alumnijournal/1032/thumbnail.jp

High-contrast imager for Complex Aperture Telescopes (HiCAT): 1. Testbed design

Searching for nearby habitable worlds with direct imaging and spectroscopy will require a telescope large enough to provide angular resolution and sensitivity to planets around a significant sample of stars. Segmented telescopes are a compelling option to obtain such large apertures. However, these telescope designs have a complex geometry (central obstruction, support structures, segmentation) that makes high-contrast imaging more challenging. We are developing a new high-contrast imaging testbed at STScI to provide an integrated solution for wavefront control and starlight suppression on complex aperture geometries. We present our approach for the testbed optical design, which defines the surface requirements for each mirror to minimize the amplitude-induced errors from the propagation of out-of-pupil surfaces. Our approach guarantees that the testbed will not be limited by these Fresnel propagation effects, but only by the aperture geometry. This approach involves iterations between classical ray-tracing optical design optimization, and end-to-end Fresnel propagation with wavefront control (e.g. Electric Field Conjugation / Stroke Minimization). The construction of the testbed is planned to start in late Fall 2013.Comment: Proc. of the SPIE 8864, 10 pages, 3 figures, Techniques and Instrumentation for Detection of Exoplanets V