A. J. E. Smith

The Dark Energy Survey and operations: Year 1

The Dark Energy Survey (DES) is a next generation optical survey aimed at understanding the accelerating expansion of the universe using four complementary methods: weak gravitational lensing, galaxy cluster counts, baryon acoustic oscillations, and Type Ia supernovae. To perform the 5000 sq-degree wide field and 30 sq-degree supernova surveys, the DES Collaboration built the Dark Energy Camera (DECam), a 3 square-degree, 570-Megapixel CCD camera that was installed at the prime focus of the Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory (CTIO). DES started its first observing season on August 31, 2013 and observed for 105 nights through mid-February 2014. This paper describes DES “Year 1” (Y1), the strategy and goals for the first years data, provides an outline of the operations procedures, lists the efficiency of survey operations and the causes of lost observing time, provides details about the quality of the first years data, and hints at the “Year 2” plan and outlook.

PRECISION DETERMINATION OF ATMOSPHERIC EXTINCTION AT OPTICAL AND NEAR-INFRARED WAVELENGTHS

The science goals for future ground-based all-sky surveys, such as the Dark Energy Survey, PanSTARRS, and the Large Synoptic Survey Telescope, require calibration of broadband photometry that is stable in time and uniform over the sky to precisions of 1% or better, and absolute calibration of color measurements that are similarly accurate. This performance will need to be achieved with measurements made from multiple images taken over the course of many years, and these surveys will observe in less than ideal conditions. This paper describes a technique to implement a new strategy to directly measure variations of atmospheric transmittance at optical wavelengths and application of these measurements to calibration of ground-based observations. This strategy makes use of measurements of the spectra of a small catalog of bright probe stars as they progress across the sky and back-light the atmosphere. The signatures of optical absorption by different atmospheric constituents are recognized in these spectra by their characteristic dependences on wavelength and airmass. State-of-the-art models of atmospheric radiation transport and modern codes are used to accurately compute atmospheric extinction over a wide range of observing conditions. We present results of an observing campaign that demonstrate that correction for extinction due to molecular constituents and aerosols can be done with precisions of a few millimagnitudes with this technique.

Calibration of the LSST instrumental and atmospheric photometric passbands

The Large Synoptic Survey Telescope (LSST) will continuously image the entire sky visible from Cerro Pachon in northern Chile every 3-4 nights throughout the year. The LSST will provide data for a broad range of science investigations that require better than 1% photometric precision across the sky (repeatability and uniformity) and a similar accuracy of measured broadband color. The fast and persistent cadence of the LSST survey will significantly improve the temporal sampling rate with which celestial events and motions are tracked. To achieve these goals, and to optimally utilize the observing calendar, it will be necessary to obtain excellent photometric calibration of data taken over a wide range of observing conditions - even those not normally considered photometric. To achieve this it will be necessary to routinely and accurately measure the full optical passband that includes the atmosphere as well as the instrumental telescope and camera system. The LSST mountain facility will include a new monochromatic dome illumination projector system to measure the detailed wavelength dependence of the instrumental passband for each channel in the system. The facility will also include an auxiliary spectroscopic telescope dedicated to measurement of atmospheric transparency at all locations in the sky during LSST observing. In this paper, we describe these systems and present laboratory and observational data that illustrate their performance.

The Moss Flora of Britain and Ireland: Abbreviations

This book describes and illustrates in detail the 763 species of mosses currently known to occur in the British Isles and incorporates the most up-to-date information available on classification and nomenclature, together with recent synonyms. The species descriptions provide information on frequency, ecology, geographical relationships and distribution, including information on protected species and those species at risk. For many species there are footnotes to aid identification. In addition to the species descriptions there are descriptions of families and genera and also introductory information on conservation, collection, preservation and examination of material, together with advice on using the keys. An artificial key to genera provides the only workable comprehensive key published in the English language. As a further aid to the user a list of English names for all British mosses is included, plus a comprehensive glossary and bibliography. This second edition incorporates the very considerable advances in knowledge of mosses made in the last quarter of the twentieth century. In this time eight species new to science have been described in Britain, 25 species not previously known in the British Isles have been discovered and taxonomic revisions have led to the addition of a further 51 species. Fourteen species have been removed, bringing the total number of species described to 763. Additionally, modern taxonomic methods have led to an increase in the number of genera from 175 to 214. This thoroughly updated and comprehensive Flora represents a unique resource for all those interested in this fascinating group of organisms

The Moss Flora of Britain and Ireland: Index

This book describes and illustrates in detail the 763 species of mosses currently known to occur in the British Isles and incorporates the most up-to-date information available on classification and nomenclature, together with recent synonyms. The species descriptions provide information on frequency, ecology, geographical relationships and distribution, including information on protected species and those species at risk. For many species there are footnotes to aid identification. In addition to the species descriptions there are descriptions of families and genera and also introductory information on conservation, collection, preservation and examination of material, together with advice on using the keys. An artificial key to genera provides the only workable comprehensive key published in the English language. As a further aid to the user a list of English names for all British mosses is included, plus a comprehensive glossary and bibliography. This second edition incorporates the very considerable advances in knowledge of mosses made in the last quarter of the twentieth century. In this time eight species new to science have been described in Britain, 25 species not previously known in the British Isles have been discovered and taxonomic revisions have led to the addition of a further 51 species. Fourteen species have been removed, bringing the total number of species described to 763. Additionally, modern taxonomic methods have led to an increase in the number of genera from 175 to 214. This thoroughly updated and comprehensive Flora represents a unique resource for all those interested in this fascinating group of organisms

The Moss Flora of Britain and Ireland: Frontmatter

This book describes and illustrates in detail the 763 species of mosses currently known to occur in the British Isles and incorporates the most up-to-date information available on classification and nomenclature, together with recent synonyms. The species descriptions provide information on frequency, ecology, geographical relationships and distribution, including information on protected species and those species at risk. For many species there are footnotes to aid identification. In addition to the species descriptions there are descriptions of families and genera and also introductory information on conservation, collection, preservation and examination of material, together with advice on using the keys. An artificial key to genera provides the only workable comprehensive key published in the English language. As a further aid to the user a list of English names for all British mosses is included, plus a comprehensive glossary and bibliography. This second edition incorporates the very considerable advances in knowledge of mosses made in the last quarter of the twentieth century. In this time eight species new to science have been described in Britain, 25 species not previously known in the British Isles have been discovered and taxonomic revisions have led to the addition of a further 51 species. Fourteen species have been removed, bringing the total number of species described to 763. Additionally, modern taxonomic methods have led to an increase in the number of genera from 175 to 214. This thoroughly updated and comprehensive Flora represents a unique resource for all those interested in this fascinating group of organisms