498 research outputs found

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    Identification and Removal of Noise Modes in Kepler Photometry

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    We present the Transiting Exoearth Robust Reduction Algorithm (TERRA) --- a novel framework for identifying and removing instrumental noise in Kepler photometry. We identify instrumental noise modes by finding common trends in a large ensemble of light curves drawn from the entire Kepler field of view. Strategically, these noise modes can be optimized to reveal transits having a specified range of timescales. For Kepler target stars of low photometric noise, TERRA produces ensemble-calibrated photometry having 33 ppm RMS scatter in 12-hour bins, rendering individual transits of earth-size planets around sun-like stars detectable as ~3 sigma signals.Comment: 18 pages, 7 figures, submitted to PAS

    Global Erratum for Kepler Q0-Q17 and K2 C0-C5 Short Cadence Data

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    An accounting error has scrambled much of the short-cadence collateral smear data used to correct for the effects of Keplers shutterless readout. This error has been present since launch and affects approximately half of all short-cadence targets observed by Kepler and K2 to date. The resulting calibration errors are present in both the short-cadence target pixel files and the short-cadence light curves for Kepler Data Releases 1-24 and K2 Data Releases 1-7. This error does not affect long-cadence data. Since it will take some time to correct this error and reprocess all Kepler and K2 data, a list of affected targets is provided. Even though the affected targets are readily identified, the science impact for any particular target may be difficult to assess. Since the smear signal is often small compared to the target signal, the effect is negligible for many targets. However, the smear signal is scene-dependent, so time varying signals can be introduced into any target by the other stars falling on the same CCD column. Some tips on how to assess the severity of the calibration error are provided in this document

    Not Just a Theory—The Utility of Mathematical Models in Evolutionary Biology

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    Models have made numerous contributions to evolutionary biology, but misunderstandings persist regarding their purpose. By formally testing the logic of verbal hypotheses, proof-of-concept models clarify thinking, uncover hidden assumptions, and spur new directions of study. thumbnail image credit: modified from the Biodiversity Heritage Librar

    Kepler Archive Manual

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    A description of Kepler, its design, performance and operational constraints may be found in the Kepler Instrument Handbook (KIH, Van Cleve Caldwell 2016). A description of Kepler calibration and data processing is described in the Kepler Data Processing Handbook (KDPH, Jenkins et al. 2016; Fanelli et al. 2011). Science users should also consult the special ApJ Letters devoted to early Kepler results and mission design (April 2010, ApJL, Vol. 713 L79-L207). Additional technical details regarding the data processing and data qualities can be found in the Kepler Data Characteristics Handbook (KDCH, Christiansen et al. 2013) and the Data Release Notes (DRN). This archive manual specifically documents the file formats, as they exist for the last data release of Kepler, Data Release 25(KSCI-19065-002). The earlier versions of the archive manual and data release notes act as documentation for the earlier versions of the data files

    Offshore Wind Energy Permitting: A Survey of U.S. Project Developers

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    The U.S. Department of Energy (DOE) has adopted a goal to generate 20% of the nation’s electricity from wind power by 2030. Achieving this “20% Wind Scenario” in 2030 requires acceleration of the current rate of wind project development. Offshore wind resources contribute substantially to the nation’s wind resource, yet to date no offshore wind turbines have been installed in the U.S. Progress developing offshore wind projects has been slowed by technological challenges, uncertainties about impacts to the marine environment, siting and permitting challenges, and viewshed concerns. To address challenges associated with siting and permitting, Pacific Northwest National Laboratory (PNNL) surveyed offshore wind project developers about siting and project development processes, their experience with the environmental permitting process, and the role of coastal and marine spatial planning (CMSP) in development of the offshore wind industry. Based on the responses to survey questions, we identify several priority recommendations to support offshore wind development. Recommendations also include considerations for developing supporting industries in the U.S. and how to use Coastal and Marine Spatial Planning (CMSP) to appropriately consider ocean energy among existing ocean uses. In this report, we summarize findings, discuss the implications, and suggest actions to improve the permitting and siting process

    Information-theoretic interpretation of quantum error-correcting codes

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    Quantum error-correcting codes are analyzed from an information-theoretic perspective centered on quantum conditional and mutual entropies. This approach parallels the description of classical error correction in Shannon theory, while clarifying the differences between classical and quantum codes. More specifically, it is shown how quantum information theory accounts for the fact that "redundant" information can be distributed over quantum bits even though this does not violate the quantum "no-cloning" theorem. Such a remarkable feature, which has no counterpart for classical codes, is related to the property that the ternary mutual entropy vanishes for a tripartite system in a pure state. This information-theoretic description of quantum coding is used to derive the quantum analogue of the Singleton bound on the number of logical bits that can be preserved by a code of fixed length which can recover a given number of errors.Comment: 14 pages RevTeX, 8 Postscript figures. Added appendix. To appear in Phys. Rev.

    Environmental Risk Evaluation System (ERES) for Offshore Wind - Mock-Up of ERES, Fiscal Year 2010 Progress Report

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    The Environmental Risk Evaluation System (ERES) has been created to set priorities among the environmental risks from offshore wind development. This report follows the conceptual design for ERES and shows what the system would look like, using a web interface created as part of a Knowledge Management System (KMS) for offshore wind. The KMS, called Zephyrus, and ERES for offshore wind, will be populated and made operational in a later phase of the project

    Initial Characteristics of Kepler Short Cadence Data

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    The Kepler Mission offers two options for observations -- either Long Cadence (LC) used for the bulk of core mission science, or Short Cadence (SC) which is used for applications such as asteroseismology of solar-like stars and transit timing measurements of exoplanets where the 1-minute sampling is critical. We discuss the characteristics of SC data obtained in the 33.5-day long Quarter 1 (Q1) observations with Kepler which completed on 15 June 2009. The truly excellent time series precisions are nearly Poisson limited at 11th magnitude providing per-point measurement errors of 200 parts-per-million per minute. For extremely saturated stars near 7th magnitude precisions of 40 ppm are reached, while for background limited measurements at 17th magnitude precisions of 7 mmag are maintained. We note the presence of two additive artifacts, one that generates regularly spaced peaks in frequency, and one that involves additive offsets in the time domain inversely proportional to stellar brightness. The difference between LC and SC sampling is illustrated for transit observations of TrES-2.Comment: 5 pages, 4 figures, ApJ Letters in pres
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