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Caltech Authors (138.832 recursos)

Repository of works by Caltech published authors.

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Mostrando recursos 1 - 20 de 6.819

  1. The Herschel Point Source Catalogue

    Marton, G.; Schulz, B.; Altieri, B.; Calzoletti, L.; Kiss, Cs.; Lim, T.; Lu, N.; Paladini, R.; Papageorgiou, A.; Pearson, C.; Rector, J.; Shupe, D.; Valtchanov, I.; Verebélyi, E.; Xu, K.
    The Herschel Space Observatory was the fourth cornerstone mission in the European Space Agency (ESA) science programme with excellent broad band imaging capabilities in the sub-mm and far-infrared part of the spectrum. Although the spacecraft finished its observations in 2013, it left a large legacy dataset that is far from having been fully scrutinised and still has a large potential for new scientific discoveries. This is specifically true for the photometric observations of the PACS and SPIRE instruments. Some source catalogues have already been produced by individual observing programs, but there are many observations that risk to remain unexplored. To...

  2. LSST Active Optics System Software Architecture

    Thomas, Sandrine J.; Lotz, P.; Chandrasekharan, Srinivasan; Xin, Bo; Claver, Charles; Angeli, George; Sebag, Jacques; Dubois-Felsmann, Gregory P.
    The Large Synoptic Survey Telescope (LSST) is an 8-meter class wide-field telescope now under construction on Cerro Pachon, near La Serena, Chile. This ground-based telescope is designed to conduct a decade-long time domain survey of the optical sky. In order to achieve the LSST scientific goals, the telescope requires delivering seeing limited image quality over the 3.5 degree field-of-view. Like many telescopes, LSST will use an Active Optics System (AOS) to correct in near real-time the system aberrations primarily introduced by gravity and temperature gradients. The LSST AOS uses a combination of 4 curvature wavefront sensors (CWS) located on the...

  3. Pre-Construction Progress of Giant Steerable Science Mirror for TMT

    Fei, Yang; Hongchao, Zhao; Qichang, An; Peng, Guo; Haibo, Jiang; Linchu, Han; Ford, Virginia; Cole, Glen; Smith, Byron; Campbell, Marvin
    The Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP) team is developing the Giant Steerable Science Mirror (GSSM) for Thirty Meter Telescope (TMT) which will enter the preliminary design phase in 2016. The GSSM is the tertiary mirror of TMT and consists of the world’s largest flat telescope mirror (approximately 3.4m X 2.4 m X 100mm thick) having an elliptical perimeter positioned with an extremely smooth tracking and pointing mechanism in a gravity-varying environment. In order to prepare for developing this unique mirror system, CIOMP has been developing a 1/4 scale, functionally accurate version of the GSSM prototype during...

  4. Unveiling the dynamic infrared sky with Gattini-IR

    Moore, Anna M.; Kasliwal, Mansi K.; Gelino, Christopher R.; Jencson, Jacob E.; Jones, Mike I.; Kirkpatrick, J. Davy; Lau, Ryan M.; Ofek, Eran; Petrunin, Yuri; Smith, Roger; Terebizh, Valery; Steinbring, Eric; Yan, Lin
    While optical and radio transient surveys have enjoyed a renaissance over the past decade, the dynamic infrared sky remains virtually unexplored. The infrared is a powerful tool for probing transient events in dusty regions that have high optical extinction, and for detecting the coolest of stars that are bright only at these wavelengths. The fundamental roadblocks in studying the infrared time-domain have been the overwhelmingly bright sky background (250 times brighter than optical) and the narrow field-of-view of infrared cameras (largest is 0.6 sq deg). To begin to address these challenges and open a new observational window in the infrared,...

  5. Capturing Complete Spatial Context in Satellite Observations of Greenhouse Gases

    Miller, Charles E.; Frankenberg, Christian; Kuhnert, Andreas C.; Spiers, Gary D.; Eldering, Annmarie; Rud, Mayer; Pagano, Thomas S.; Wilson, Daniel W.; Brooks, Cynthia; Jaffe, Daniel T.
    Scientific consensus from a 2015 pre-Decadal Survey workshop highlighted the essential need for a wide-swath (mapping) low earth orbit (LEO) instrument delivering carbon dioxide (CO_2), methane (CH_4), and carbon monoxide (CO) measurements with global coverage. OCO-2 pioneered space-based CO_2 remote sensing, but lacks the CH_4, CO and mapping capabilities required for an improved understanding of the global carbon cycle. The Carbon Balance Observatory (CARBO) advances key technologies to enable high-performance, cost-effective solutions for a space-based carbon-climate observing system. CARBO is a compact, modular, 15-30° field of view spectrometer that delivers high-precision CO_2, CH_4, CO and solar induced chlorophyll fluorescence (SIF)...

  6. TMT Approach to Observatory Software Development Process

    Buur, Hanne; Subramaniam, Annapurni; Gillies, Kim; Dumas, Christophe; Bhatia, Ravinder
    The purpose of the Observatory Software System (OSW) is to integrate all software and hardware components of the Thirty Meter Telescope (TMT) to enable observations and data capture; thus it is a complex software system that is defined by four principal software subsystems: Common Software (CSW), Executive Software (ESW), Data Management System (DMS) and Science Operations Support System (SOSS), all of which have interdependencies with the observatory control systems and data acquisition systems. Therefore, the software development process and plan must consider dependencies to other subsystems, manage architecture, interfaces and design, manage software scope and complexity, and standardize and optimize...

  7. LSST control software component design

    Lotz, Paul J.; Dubois-Felsmann, Gregory; Lim, Kian-Tat; Johnson, Tony; Chandrasekharan, Srinivasan; Mills, David; Daly, Philip; Schumacher, Germán; Delgado, Francisco; Pietrowicz, Steve; Selvy, Brian; Sebag, Jacques; Marshall, Stuart; Sundararaman, Harini; Contaxis, Christopher; Bovill, Robert; Jenness, Tim
    Construction of the Large Synoptic Survey Telescope system involves several different organizations, a situation that poses many challenges at the time of the software integration of the components. To ensure commonality for the purposes of usability, maintainability, and robustness, the LSST software teams have agreed to the following for system software components: a summary state machine, a manner of managing settings, a flexible solution to specify controller/controllee relationships reliably as needed, and a paradigm for responding to and communicating alarms. This paper describes these agreed solutions and the factors that motivated these.

  8. Using Predictions in Online Optimization: Looking Forward with an Eye on the Past

    Chen, Niangjun; Comden, Joshua; Liu, Zhenhua; Gandhi, Anshul; Wierman, Adam
    We consider online convex optimization (OCO) problems with switching costs and noisy predictions. While the design of online algorithms for OCO problems has received considerable attention, the design of algorithms in the context of noisy predictions is largely open. To this point, two promising algorithms have been proposed: Receding Horizon Control (RHC) and Averaging Fixed Horizon Control (AFHC). The comparison of these policies is largely open. AFHC has been shown to provide better worst-case performance, while RHC outperforms AFHC in many realistic settings. In this paper, we introduce a new class of policies, Committed Horizon Control (CHC), that generalizes both...

  9. Joint Data Purchasing and Data Placement in a Geo-Distributed Data Market

    Ren, Xiaoqi; London, Palma; Ziani, Juba; Wierman, Adam
    This paper studies design challenges faced by a geo-distributed cloud data market: which data to purchase (data purchasing) and where to place/replicate the data (data placement). We show that the joint problem of data purchasing and data placement within a cloud data market is NP-hard in general. However, we give a provably optimal algorithm for the case of a data market made up of a single data center, and then generalize the structure from the single data center setting and propose Datum, a near-optimal, polynomial-time algorithm for a geo-distributed data market.

  10. Theory and implementation of a distributed event based platform

    Chandy, K. Mani
    This paper presents theory and an implementation of a Distributed Event Based System (DEBS) platform. The theory is based on a simple model that forms the basis of the implementation. Though this paper is about a DEBS platform, a description of the theory and model provides the motivation for the design. Many software libraries operate on "data at rest', i.e. fixed data structures such as arrays and graphs. By contrast, DEBS systems operate on "data in motion," i.e., data structures that change, in increments, over time. Many software libraries are designed for sequential execution or synchronous parallel execution. By contrast, DEBS...

  11. Vector field processing on triangle meshes

    de Goes, Fernando; Desbrun, Mathieu; Tong, Yiying
    While scalar fields on surfaces have been staples of geometry processing, the use of tangent vector fields has steadily grown in geometry processing over the last two decades: they are crucial to encode both directions and sizing on surfaces as commonly required in tasks such as texture synthesis, non-photorealistic rendering, digital grooming, and meshing. There are, however, a variety of discrete representations of tangent vector fields on triangle meshes, and each approach offers different trade-offs among simplicity, efficiency, and accuracy depending on the targeted application. This course reviews the three main families of discretizations used to design computational tools for vector...

  12. Understanding jokes: a neural approach to content-based information retrieval

    Zrehen, Stephane; Arbib, Michael A.
    This paper addresses the problem of accessing the content of documents. Drawing from similarities between vision and language, we devise a neural adaptive architecture that can detect and use context information for the ‘understanding” of content, The functioning of this architecture is illustrated by the problem of understanding jokes.

  13. Interactive multiresolution mesh editing

    Zorin, Denis; Schröder, Peter; Sweldens, Wim
    We describe a multiresolution representation for meshes based on subdivision, which is a natural extension of the existing patch-based surface representations. Combining subdivision and the smoothing algorithms of Taubin [26] allows us to construct a set of algorithms for interactive multiresolution editing of complex hierarchical meshes of arbitrary topology. The simplicity of the underlying algorithms for refinement and coarsification enables us to make them local and adaptive, thereby considerably improving their efficiency. We have built a scalable interactive multiresolution editing system based on such algorithms.

  14. Interpolating Subdivision for meshes with arbitrary topology

    Zorin, Denis; Schröder, Peter; Sweldens, Wim
    Subdivision is a powerful paradigm for the generation of surfaces of arbitrary topology. Given an initial triangular mesh the goal is to produce a smooth and visually pleasing surface whose shape is controlled by the initial mesh. Of particular interest are interpolating schemes since they match the original data exactly, and play an important role in fast multiresolution and wavelet techniques. Dyn, Gregory, and Levin introduced the Butterfly scheme, which yields C^1 surfaces in the topologically regular setting. Unfortunately it exhibits undesirable artifacts in the case of an irregular topology. We examine these failures and derive an improved scheme, which retains the...

  15. Correction of geometric perceptual distortions in pictures

    Zorin, Denis; Barr, Alan H.
    We suggest an approach for correcting several types of perceived geometric distortions in computer-generated and photographic images. The approach is based on a mathematical formalization of desirable properties of pictures. From a small set of simple assumptions we obtain perceptually preferable viewing transformations and show that these transformations can be decomposed into a perspective or parallel projection followed by a planar transformation. The decomposition is easily implemented and provides a convenient framework for further analysis of the image mapping. We prove that two perceptually important properties are incompatible and cannot be satisfied simultaneously. It is impossible to construct a viewing transformation such that...

  16. Semi-regular mesh extraction from volumes

    Wood, Zoë J.; Desbrun, Mathieu; Schröder, Peter; Breen, David
    We present a novel method to extract iso-surfaces from distance volumes. It generates high quality semi-regular multiresolution meshes of arbitrary topology. Our technique proceeds in two stages. First, a very coarse mesh with guaranteed topology is extracted. Subsequently an iterative multi-scale force-based solver refines the initial mesh into a semi-regular mesh with geometrically adaptive sampling rate and good aspect ratio triangles. The coarse mesh extraction is performed using a new approach we call surface wavefront propagation. A set of discrete iso-distance ribbons are rapidly built and connected while respecting the topology of the iso-surface implied by the data. Subsequent multi-scale...

  17. Black hole electromagnetic duality

    Deser, S.
    After defining the concept of duality in the context of general n-form abelian gauge fields in 2n dimensions, we show by explicit example the difference between apparent but unrealizable duality transformations, namely those in D = 4k + 2, and those, in D = 4k, that can be implemented by explicit dynamical generators. We then consider duality transformations in Maxwell theory in the presence of gravitation, particularly electrically and magnetically charged black hole geometrics. By comparing actions in which both the dynamical variables and the charge parameters are “rotated,” we show their equality for equally charged electric and magnetic black...

  18. The NOAO Data Lab virtual storage system

    Graham, Matthew J.; Fitzpatrick, Michael J.; Norris, Patrick; Mighell, Kenneth J.; Olsen, Knut; Stobie, Elizabeth B.; Ridgway, Stephen T.; Bolton, Adam S.; Saha, Abhijit; Huang, Lijuan
    Collaborative research/computing environments are essential for working with the next generations of large astronomical data sets. A key component of them is a distributed storage system to enable data hosting, sharing, and publication. VOSpace is a lightweight interface providing network access to arbitrary backend storage solutions and endorsed by the International Virtual Observatory Alliance (IVOA). Although similar APIs exist, such as Amazon S3, WebDav, and Dropbox, VOSpace is designed to be protocol agnostic, focusing on data control operations, and supports asynchronous and third-party data transfers, thereby minimizing unnecessary data transfers. It also allows arbitrary computations to be triggered as a...

  19. Firefly: Embracing Future Web Technologies

    Roby, W.; Wu, X.; Goldina, T.; Joliet, E.; Ly, L.; Mi, W.; Wang, C.; Zhang, Lijun; Ciardi, D.; Dubois-Felsmann , G.
    At IPAC/Caltech, we have developed the Firefly web archive and visualization system. Used in production for the last eight years in many missions, Firefly gives the scientist significant capabilities to study data. Firefly provided the first completely web based FITS viewer as well as a growing set of tabular and plotting visualizers. Further, it will be used for the science user interface of the LSST telescope which goes online in 2021. Firefly must meet the needs of archive access and visualization for the 2021 LSST telescope and must serve astronomers beyond the year 2030. Recently, our team has faced the...

  20. The Infrared Imaging Spectrograph (IRIS) for TMT: motion planning with collision avoidance for the on-instrument wavefront sensors

    Chapin, Edward L.; Dunn, Jennifer; Weiss, Jason; Gillies, Kim; Hayano, Yutaka; Johnson, Chris; Larkin, James; Moore, Anna; Riddle, Reed L.; Sohn, Ji Man; Smith, Roger; Suzuki, Ryuji; Walth, Gregory; Wright, Shelley
    The InfraRed Imaging Spectrograph (IRIS) will be a first-light client instrument for the Narrow Field Infrared Adaptive Optics System (NFIRAOS) on the Thirty Meter Telescope. IRIS includes three configurable tip/tilt (TT) or tip/tilt/focus (TTF) On-Instrument Wavefront Sensors (OIWFS). These sensors are positioned over natural guide star (NGS) asterisms using movable polar-coordinate pick-ofi arms (POA) that patrol an approximately 2-arcminute circular field-of-view (FOV). The POAs are capable of colliding with one another, so an algorithm for coordinated motion that avoids contact is required. We have adopted an approach in which arm motion is evaluated using the gradient descent of a scalar...

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