278,092 research outputs found

    New Completeness Methods for Estimating Exoplanet Discoveries by Direct Detection

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    We report new methods for evaluating realistic observing programs that search stars for planets by direct imaging, where observations are selected from an optimized star list, and where stars can be observed multiple times. We show how these methods bring critical insight into the design of the mission & its instruments. These methods provide an estimate of the outcome of the observing program: the probability distribution of discoveries (detection and/or characterization), & an estimate of the occurrence rate of planets (eta). We show that these parameters can be accurately estimated from a single mission simulation, without the need for a complete Monte Carlo mission simulation, & we prove the accuracy of this new approach. Our methods provide the tools to define a mission for a particular science goal, for example defined by the expected number of discoveries and its confidence level. We detail how an optimized star list can be built & how successive observations can be selected. Our approach also provides other critical mission attributes, such as the number of stars expected to be searched, & the probability of zero discoveries. Because these attributes depend strongly on the mission scale, our methods are directly applicable to the design of such future missions & provide guidance to the mission & instrument design based on scientific performance. We illustrate our new methods with practical calculations & exploratory design reference missions for JWST operating with a distant starshade to reduce scattered and diffracted starlight on the focal plane. We estimate that 5 habitable Earth-mass planets would be discovered & characterized with spectroscopy, with a probability of 0 discoveries of 0.004, assuming a small fraction of JWST observing time (7%), eta=0.3, and 70 observing visits, limited by starshade fuel.Comment: 27 pages, 4 figures, 6 tables, accepted for publication by Ap

    Asking questions

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    Intimacy with strangers

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    Nottingham rules: Andrew Brown reports from this year's nottdance festival

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    Moving in mysterious ways

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    1973 Evaluations of Some Pesticide Residues in Food: The Monographs. Food and Agriculture Organization of the United Nations, Rome, 1975. 491 p. Available from Unipub, Box 433, Murray Hill Station, New York, NY 10016. $15.00.

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    (excerpt) The evaluations of residues on foodstuffs contained in these monographs were prepared by a joint meeting of an FA0 expert committee and a WHO expert committee on pesticide residues that met in Geneva and produced its report Pesticide Residues in Food published as WHO Technical Report Series No. 545 and FA0 Agricultural Studies No. 92 in 1974. Th
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