Showing papers in "Astronomical Telescopes and Instrumentation in 2002"
TL;DR: In this article, the authors describe the motivation for a distributed aperture approach for the LSST, the current concept for Pan-STARRS, and its performance goals and science reach.
Abstract: The IFA and collaborators are embarking on a project to develop a 4-telescope synoptic survey instrument. While somewhat smaller than the 6.5m class telescope envisaged by the decadal review in their proposal for a LSST, this facility will nonetheless be able to accomplish many of the LSST science goals. In this paper we will describe the motivation for a 'distributed aperture' approach for the LSST, the current concept for Pan-STARRS -- a pilot project for the LSST proper -- and its performance goals and science reach. We will also discuss how the facility may be expanded.
720 citations
TL;DR: The Nearby Supernova Factory (SNfactory) as mentioned in this paper is an international experiment designed to lay the foundation for the next generation of cosmology experiments (such as CFHTLS, wP, SNAP and LSST) which will measure the expansion history of the Universe using Type Ia supernovae.
Abstract: Overview of the Nearby Supernova Factory G. Aldering a , G. Adam b , P. Antilogus c , P. Astier d , R. Bacon b , S. Bongard c , C. Bonnaud b , Y. Copin c , D. Hardin d , F. Henault b , D. A. Howell a , J.-P. Lemonnier b , J.-M. Levy d , S. Loken a , P. Nugent a , R. Pain d , A. Pecontal b , E. Pecontal b , S. Perlmutter a , R. Quimby a , K. Schahmaneche d , G. Smadja c , and W.M. Wood-Vasey a , the Nearby Supernova Factory collaboration Berkeley National Laboratory, Berkeley CA, USA de Recherche Astronomique, Universite Lyon I and Ecole Normale Superieure, Lyon, France c Institut de Physique Nucleaire, Universite Lyon I, Lyon, France d Laboratoire de Physique Nucleaire et de Hautes Energies, Universites Paris VI and VII, Paris, France b Centre a Lawrence ABSTRACT The Nearby Supernova Factory (SNfactory) is an international experiment designed to lay the foundation for the next generation of cosmology experiments (such as CFHTLS, wP, SNAP and LSST) which will measure the expansion history of the Universe using Type Ia supernovae. The SNfactory will discover and obtain frequent lightcurve spectrophotome- try covering 3200-10000 A for roughly 300 Type Ia supernovae at the low-redshift end of the smooth Hubble flow. The quantity, quality, breadth of galactic environments, and homogeneous nature of the SNfactory dataset will make it the premier source of calibration for the Type Ia supernova width-brightness relation and the intrinsic supernova colors used for K-correction and correction for extinction by host-galaxy dust. This dataset will also allow an extensive investiga- tion of additional parameters which possibly influence the quality of Type Ia supernovae as cosmological probes. The SNfactory search capabilities and follow-up instrumentation include wide-field CCD imagers on two 1.2-m telescopes (via collaboration with the Near Earth Asteroid Tracking team at JPL and the QUEST team at Yale), and a two-channel integral-field-unit optical spectrograph/imager being fabricated for the University of Hawaii 2.2-m telescope. In addition to ground-based follow-up, UV spectra for a subsample of these supernovae will be obtained with HST. The pipeline to obtain, transfer via wireless and standard internet, and automatically process the search images is in operation. Software and hardware development is now underway to enable the execution of follow-up spectroscopy of supernova candidates at the Hawaii 2.2-m telescope via automated remote control of the telescope and the IFU spectrograph/imager. Keywords: supernova, survey, cosmology, integral-field-unit, spectrograph 1. PROBING DARK ENERGY WITH SUPERNOVAE A coherent view of the universe is emerging in which a mysterious form of “dark energy” accounts for about 2/3 of the total energy density in the Universe. Direct evidence for this radical conclusion comes from distance measurements of Type Ia supernovae (SNe Ia; see Fig. 1) which indicate the expansion of the Universe is not slowing down as would be expected in a Universe filled with only matter and radiation. 1, 2 Further support for this result has come from recent measurements of the CMB indicating a flat universe, 3 combined with determinations of Ω M ∼ 0.3 from structure formation. SNe Ia remain the most mature cosmological distance indicator, and therefore, offer the best current means of exper- imentally probing the properties of the dark energy. Their cosmological use was developed in the early 1990’s, paving the way for the discovery of dark energy. 1, 4–10 Now similar developmental efforts are needed so that the next order of magnitude improvement of the experimental constraints on the properties of dark energy can be made. Progress must be made on two fronts, at a level which cannot be pursued with existing programs alone. First a large number of nearby SNe must be observed in an appropriate fashion since they provide the fulcrum of the lever-arm needed to make cosmological inferences from high-redshift SNe observations. Furthermore, these SNe provide the critical Correspondence: e-mail galdering@lbl.gov; telephone 510-495-2203
309 citations
TL;DR: The LSST as discussed by the authors is a 8.4 m telescope with a 3 degree field of view and an optical throughput of 260 m2 deg2 with a dedicated all-sky monitoring mode.
Abstract: A large wide-field telescope and camera with optical throughput over 200 m2 deg2 -- a factor of 50 beyond what we currently have -- would enable the detection of faint moving or bursting optical objects: from Earth threatening asteroids to energetic events at the edge of the optical universe. An optimized design for LSST is a 8.4 m telescope with a 3 degree field of view and an optical throughput of 260 m2 deg2. With its large throughput and dedicated all-sky monitoring mode, the LSST will reach 24th magnitude in a single 10 second exposure, opening unexplored regions of astronomical parameter space. The heart of the 2.3 Gpixel camera will be an array of imager modules with 10 μm pixels. Once each month LSST will survey up to 14,000 deg2 of the sky with many ~10 second exposures. Over time LSST will survey 30,000 deg2 deeply in multiple bandpasses, enabling innovative investigations ranging from galactic structure to cosmology. This is a shift in paradigm for optical astronomy: from "survey follow-up" to "survey direct science." The resulting real-time data products and fifteen petabyte time-tagged imaging database and photometric catalog will provide a unique resource. A collaboration of ~80 engineers and scientists are gearing up to confront this exciting challenge.
303 citations
TL;DR: The SDSS project has taken 5-band data covering approximately 3000 deg2, or 4Tby of data, and the resulting catalogues of about 100 million objects have been used for a number of scientific projects.
Abstract: The SDSS project has taken 5-band data covering approximately 3000 deg 2 , or 4Tby of data. This has been processed through a set of image-processing pipelines, and the resulting catalogues of about 100 million objects have been used for a number of scientific projects.
We discuss our software infrastructure, and outline the architecture of the SDSS image processing pipelines. In order to process this volume of data the pipelines have to be robust and reasonably fast; because we have been interested in looking for rare objects, the number of outliers due to deficiencies in the data and bugs in the software must be small. We have found that writing the codes has been one of the harder and more expensive aspects of the entire survey.
123 citations
TL;DR: Improvements allow the application of blind deconvolution to very large images that are now routinely provided by telescope facilities and it is possible to explicitly cancel the normalization ambiguity and therefore improve the condition number of the problem.
Abstract: Modern blind deconvolution algorithms combine agreement with the data and regularization constraints into a single criteria (a so-called penalizing function) that must be minimized in a restricted parameter space (at least to insure positivity). Numerically speaking, blind deconvolution is a constrained optimization problem which must be solved by iterative algorithms owning to the very large number of parameters that must be estimated. Additional strong difficulties arise because blind deconvolution is intrinsically ambiguous and highly non-quadratic. This prevent the problem to be quickly solved. Various optimizations are proposed to considerably speed up blind deconvolution. These improvements allow the application of blind deconvolution to very large images that are now routinely provided by telescope facilities. First, it is possible to explicitly cancel the normalization ambiguity and therefore improve the condition number of the problem. Second, positivity can be enforced by gradient projection techniques without the need of a non-linear re-parameterization. Finally, superior convergence rates can be obtained by using a small sub-space of ad-hoc search directions derived from the effective behavior of the penalizing function.
117 citations
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Alcatel-Lucent1, Brown University2, California Institute of Technology3, University of New Mexico4, University of Washington5, Princeton University6, Drew University7, Carnegie Foundation for the Advancement of Teaching8, University of Pennsylvania9, University of Florida10, University of California, Santa Cruz11, University of Chicago12, University of Arizona13
TL;DR: The Deep Lens Survey (DLS) as mentioned in this paper is a survey of seven 2°×2° degree fields with all data to be made public, with the primary scientific driver being weak gravitational lensing.
Abstract: The Deep Lens Survey (DLS) is a deep BV Rz' imaging survey of seven 2°×2° degree fields, with all data to be made public. The primary scientific driver is weak gravitational lensing, but the survey is also designed to enable a wide array of other astrophysical investigations. A unique feature of this survey is the search for transient phenomena. We subtract multiple exposures of a field, detect differences, classify, and release transients on the Web within about an hour of observation. Here we summarize the scientific goals of the DLS, field and filter selection, observing techniques and current status, data reduction, data products and release, and transient detections. Finally, we discuss some lessons which might apply to future large surveys such as LSST.
110 citations
TL;DR: The Sloan Digital Sky Survey strategies for data publication, data access, curation, and preservation are described, observing that published scientific data needs to be available forever and gives rise to the data pyramid of versions and to data inflation where the derived data volumes explode.
Abstract: Science projects are data publishers. The scale and complexity of current and future science data changes the nature of the publication process. Publication is becoming a major project component. At a minimum, a project must preserve the ephemeral data it gathers. Derived data can be reconstructed from metadata, but metadata is ephemeral. Longer term, a project should expect some archive to preserve the data. We observe that published scientific data needs to be available forever -- this gives rise to the data pyramid of versions and to data inflation where the derived data volumes explode. As an example, this article describes the Sloan Digital Sky Survey (SDSS) strategies for data publication, data access, curation, and preservation.
93 citations
Lawrence Berkeley National Laboratory1, University of Michigan2, Stockholm University3, Centre national de la recherche scientifique4, University of Pennsylvania5, University of California, Berkeley6, Indiana University7, American Astronomical Society8, California Institute of Technology9, Space Telescope Science Institute10, Case Western Reserve University11, University of Cambridge12, Goddard Space Flight Center13
TL;DR: The SuperNova / Acceleration Probe (SNAP) as mentioned in this paper is a space-based experiment to measure the expansion history of the universe and study both its dark energy and the dark matter.
Abstract: G. Aldering a , C. Akerlof b , R. Amanullah c , P. Astier d , E. Barrelet d , C. Bebek a , L. Bergstr¨ m c , o J. Bercovitz a , G. Bernstein e , M. Bester f , A. Bonissent g , C. Bower h , W. Carithers a , E. Commins f , C. Day a , S. Deustua i , R. DiGennaro a , A. Ealet g , R. Ellis j , M. Eriksson c , A. Fruchter k , J-F. Genat d , G. Goldhaber f , A. Goobar c , D. Groom a , S. Harris f , P. Harvey f , H. Heetderks f , S. Holland a , D. Huterer l , A. Karcher a , A. Kim a , W. Kolbe a , B. Krieger a , R. Lafever a , J. Lamoureux a , M. Lampton f , M. Levi a , D. Levin b , E. Linder a , S. Loken a , o R. Malina m , R. Massey n , T. McKay b , S. McKee b , R. Miquel a , E. M¨ rtsell c , N. Mostek h , h , J. Musser h , P. Nugent a , H. Oluseyi a , R. Pain d , N. Palaio a , D. Pankow f , S. Mufson S. Perlmutter a , R. Pratt f , E. Prieto m , A. Refregier n , J. Rhodes o , K. Robinson a , N. Roe a , M. Sholl f , M. Schubnell b , G. Smadja p , G. Smoot f , A. Spadafora a , G. Tarle b , A. Tomasch b , H. von der Lippe a , D. Vincent, d J. Walder a , and G. Wang a a Lawrence Berkeley National Laboratory, Berkeley CA, USA of Michigan, Ann Arbor MI, USA c University of Stockholm, Stockholm, Sweden d CNRS/IN2P3/LPNHE, Paris, France e University of Pennsylvania, Philadelphia PA, USA f University of California, Berkeley CA, USA g CNRS/IN2P3/CPPM, Marseille, France h Indiana University, Bloomington IN, USA i American Astronomical Society, Washington DC, USA j California Institute of Technology, Pasedena CA, USA k Space Telescope Science Institute, Baltimore MD, USA l Case Western Reserve University, Cleveland OH, USA m CNRS/INSU/LAM, Marseille, France n Cambridge University, Cambridge, UK o Goddard Space Flight Center, Greenbelt MD, USA p CNRS/IN2P3/IPNL, Lyon, France b University ABSTRACT The SuperNova / Acceleration Probe (SNAP) is a space-based experiment to measure the expansion history of the Uni- verse and study both its dark energy and the dark matter. The experiment is motivated by the startling discovery that the expansion of the Universe is accelerating. A 0.7 square-degree imager comprised of 36 large format fully-depleted O -type CCD’s sharing a focal plane with 36 HgCdTe detectors forms the heart of SNAP, allowing discovery and lightcurve measurements simultaneously for many supernovae. The imager and a high-efficiency low-resolution integral field spec- trograph are coupled to a 2-m three mirror anastigmat wide-field telescope, which will be placed in a high-earth orbit. The SNAP mission can obtain high-signal-to-noise calibrated light-curves and spectra for over 2000 Type Ia supernovae ¼ ½ and 1.7. The resulting data set can not only determine the amount of dark energy with at redshifts between Þ high precision, but test the nature of the dark energy by examining its equation of state. In particular, dark energy due to a cosmological constant can be differentiated from alternatives such as “quintessence”, by measuring the dark energy’s equation of state to an accuracy of ¦¼ ¼ , and by studying its time dependence. Keywords: Early universe—instrumentation: detectors—space vehicles: instruments—supernovae:general—telescopes Correspondence: e-mail galdering@lbl.gov; telephone 510-495-2203
75 citations
TL;DR: In this article, a 5 meter aperture foldable lens was constructed from 6 panels of 1 mm thick silica; it achieved diffraction-limited performance both before and after folding.
Abstract: Eyeglass is a very large aperture (25 - 100 meter) space telescope consisting of two distinct spacecraft, separated in space by several kilometers. A diffractive lens provides the telescope's large aperture, and a separate, much smaller, space telescope serves as its mobile eyepiece. Use of a transmissive diffractive lens solves two basic problems associated with very large aperture space telescopes; it is inherently fieldable (lightweight and flat, hence packagable and deployable) and virtually eliminates the traditional, very tight, surface shape tolerances faced by reflecting apertures. The potential drawback to use of a diffractive primary (very narrow spectral bandwidth) is eliminated by corrective optics in the telescope's eyepiece. The Eyeglass can provide diffraction-limited imaging with either single-band, multiband, or continuous spectral coverage.
Broadband diffractive telescopes have been built at LLNL and have demonstrated diffraction-limited performance over a 40% spectral bandwidth (0.48 - 0.72 μm). As one approach to package a large aperture for launch, a foldable lens has been built and demonstrated. A 75 cm aperture diffractive lens was constructed from 6 panels of 1 mm thick silica; it achieved diffraction-limited performance both before and after folding. This multiple panel, folding lens, approach is currently being scaled-up at LLNL. We are building a 5 meter aperture foldable lens, involving 72 panels of 700 μm thick glass sheets, diffractively patterned to operate as coherent f/50 lens.
54 citations
TL;DR: In this article, a design for a new space surveillance telescope utilizing these curved FPA arrays is presented, which is an approach that was once taken with film, but it has not been feasible with electronic focal plane arrays (FPA).
Abstract: Ground-based surveillance of deep space has traditionally been the purview of optical telescope systems. Unlike their imaging counterparts, space surveillance telescopes emphasize wide field of view (FOV) over resolution, permitted the most rapid survey of the entire sky. At the same time there is a constant push to detect ever fainter objects, such as small pieces of space debris or small, distant asteroids. Unfortunately increased sensitivity requires very large aperture diameters, which when combined with the requirement for wide FOV results in very fast f/# telescopes. How far this set of requirements can be expanded is typically limited by large, complex, and costly corrector optics to flatten the wavefront. An alternative approach is to design the telescope to a curved focal plane. This is an approach that was once taken with film, but it has not been feasible with electronic focal plane arrays (FPA). A major break-through in FPA design may open up a new range of telescope design options. A new array fabrication technique now provides the ability to produce FPAs with a specified degree of curvature while preserving required electro-optical characteristics. This paper presents a design for a new space surveillance telescope utilizing these curved FPAs.
53 citations
TL;DR: In this article, a novel superconducting detector and readout method that could lead to photon counting, energy resolving focal plane arrays, and high spectral resolution in the optical/UV/X-ray bands is investigated.
Abstract: We are investigating a novel superconducting detector and readout method that could lead to photon counting, energy resolving focal plane arrays. This concept is intrinsically different from STJ and TES detectors, and in principle could deliver large pixel counts, high sensitivity, and Fano-limited spectral resolution in the optical/UV/X-ray bands. The readout uses the monotonic relation between the kinetic surface inductance L s of a superconductor and the density of quasiparticles n , which holds even at temperatures far below T c . This allows a sensitive readout of the number of excess quasiparticles in the detector by monitoring the transmission phase of a resonant circuit. The most intriguing aspect of this concept is that passive frequency multiplexing could be used to read out ~10 4 detectors with a single HEMT amplifier. Single x-ray events have been observed in prototype detectors.
TL;DR: Use of the Karhunen-Loeve transform allows for a particularly compact orthogonal expansion of the PSF in the deconvolution of Gemini/Hokupa'a adaptive optics images of the galactic center.
Abstract: Application of deconvolution algorithms to astronomical images is often limited by variations in PSF structure over the domain of the images. One major difficulty is that Fourier methods can no longer be used for fast convolutions over the enitre images. However, if the PSF is modeled as a sum of orthogonal functions that are individually constant in form over the images, but whose relative amplitudes encode the PSF spatial variability, then separation of variables again allows global image operations to be used. This approach is readily adapted to the Lucy-Richardson deconvolution algorithm. Use of the Karhunen-Loeve transform allows for a particularly compact orthogonal expansion of the PSF. These techniques are demonstrated on the deconvolution of Gemini/Hokupa'a adaptive optics images of the galactic center.
TL;DR: The Rapid Telescopes for Optical Response (RAPTOR) experiment as discussed by the authors is a spatially distributed system of autonomous robotic telescopes that is designed to monitor the sky for optical transients.
Abstract: The Rapid Telescopes for Optical Response (RAPTOR) experiment is a spatially distributed system of autonomous robotic telescopes that is designed to monitor the sky for optical transients. The core of the ystem is composed of two telescope arrays, separated by 38 kilometers, that stereoscopically view the same 1500 square-degree field with a wide-field imaging array and a central 4 square-degree field with a more sensitive narrow-field ``fovea" imager. Coupled to each telescope array is a real-time data analysis pipeline that is designed to identify interesting transients on timescales of seconds and, when a celestial transient is identified, to command the rapidly slewing robotic mounts to point the narrow-field ``fovea'' imagers at the transient. The two narrow-field telescopes then image the transient with higher spatial resolution and at a faster cadence to gather light curve information. Each ``fovea" camera also images the transient through a different filter to provide color information. This stereoscopic monitoring array is supplemented by a rapidly slewing telescope with a low resolution spectrograph for follow-up observations of transients and a sky patrol telescope that nightly monitors about 10,000 square-degrees for variations, with timescales of a day or longer, to a depth about 100 times fainter. In addition to searching for fast transients, we will use the data stream from RAPTOR as a real-time sentinel for recognizing important variations in known sources. All of the data will be publically released through a virtual observatory called SkyDOT (Sky Database for Objects in the Time Domain) that we are developing for studying variability of the optical sky. Altogether, the RAPTOR project aims to construct a new type of system for discovery in optical astronomy---one that explores the time domain by "mining the sky in real time".© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: In this paper, an efficient control of a membrane reflector shape can be achieved using embedded actuators distributed over the membrane surface, using only local information about errors and actuation for collocated and neighboring positions in each of the distributed computational elements.
Abstract: Large, lightweight telescopes in space will enable future earth science, space science, and reconnaissance. The state of the art in space telescope is the Hubble Space Telescope launched in 1990 with its 2.4 m primary mirror. Missions within the decade such as the Next Generation Space Telescope will push this aperture diameter to over 6.5 m. But truly revolutionary observation in many wavelengths will require increasingly large and lightweight apertures. Although these telescopes of the future will have low areal mass density, the deployed aperture structures must capture and hold a surface figure to a fraction of a wavelength in the presence of thermal, slew, and vibration disturbances. Active control of surface figure is a key technology for the success of gossamer space structures. For structures with thousands of actuators distributed in the surface, the control hardware and computations should be distributed as well. This paper discusses how an efficient control of a membrane reflector shape can be achieved using embedded actuators distributed over the membrane surface. Advanced algorithms using only local information about errors and actuation for collocated and neighboring positions in each of the distributed computational elements allow achieving required control performance. Electrostatic actuators implemented on compliant plastic substrates, represent a highly attractive proposition thanks to their very low areal density. Control, sensing, and communication is distributed and integrated in the adaptive membrane to provide the imaging surface quality of a thick stiff mirror at an infinitesimal fraction of the mass. An adaptive membrane with built-in distributed actuators, sensors, and computational elements can be made scalable to a very large size.
TL;DR: In this article, a vector/matrix algorithm for generating pointing predictions on an imperfect telescope, with support for autoguiding, field stabilization and world coordinate systems even in difficult cases such as Nasmyth and coude, was proposed.
Abstract: A typical modern telescope control system points by first calculating the direction of the target in nominal mount coordinates and then applying small corrections to the demanded mount angles. The pointing refers to the rotation axis of the instrument mount, and rotator demands are calculated via parallactic angle. This simple approach works well enough when the corrections are small and the accuracy objectives are modest. However, a more rigorous approach can pay off, in the form of improved pointing, more accurate guide probe predictions, reduced residual field rotation and reliable world coordinate system information even when the detector is off-axis. In this paper I propose a rigorous vector/matrix algorithm for generating pointing predictions on an imperfect telescope, with support for autoguiding, field stabilization and world coordinate systems even in difficult cases such as Nasmyth and coude.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: In this article, the development of thin-shell, nano-laminate mirror substrates that are capable of being electroactively figured is discussed, which has the potential to substantially reduce the cost of space-based optics by allowing replication of ultra-lightweight primary mirrors from a master precision tool.
Abstract: The space science community has identified a need for ultra-light weight, large aperture optical systems that are capable of producing high-resolution images of low contrast. Current mirror technologies are limited due either to not being scalable to larger sizes at reasonable masses, or to lack of surface finish, dimensional stability in a space environment or long fabrication times.
This paper will discuss the development of thin-shell, nano-laminate mirror substrates that are capable of being electro-actively figured. This technology has the potential to substantially reduce the cost of space based optics by allowing replication of ultra-lightweight primary mirrors from a master precision tool. Precision master tools have been shown to be used multiple times with repeatable surface quality results with less than one week fabrication times for the primary optical mirror substrate. Current development has developed a series of 0.25 and 0.5 meter spherical nanolaminate mirrors that are less than 0.5 kg/m 2 areal density before electroactive components are mounted, and a target of less than 2.0 kg/m with control elements. This paper will provide an overview of nanolaminate materials for optical mirrors, modeling of their behavior under figure control and experiments conducted to validate precision control.
TL;DR: The first public release of the SDSS Moving Object Catalog (SOC) was made by as discussed by the authors, with observations for 58,117 asteroids, including 10,592 previously known objects.
Abstract: We announce the first public release of the SDSS Moving Object Catalog, with SDSS observations for 58,117 asteroids. The catalog lists astrometric and photometric data for moving objects observed prior to Dec 15, 2001, and also includes orbital elements for 10,592 previously known objects, and confirm that asteroid dynamical families, defined as clusters in orbital parameter space, also strongly segregate in color space. Their distinctive optical colors indicate that the variations in chemical composition within a family are much smaller than the compositional differences between families, and strongly support earlier suggestions that asteroids belonging to a particular family have a common origin.
TL;DR: The WIYN One Degree Imager (ODI) as mentioned in this paper is a well-sampled (0.11" per pixel) imager that provides a full one degree square field of view (32K×32K pixels).
Abstract: The WIYN One Degree Imager (ODI) will be a well-sampled (0.11” per pixel) imager that provides a full one degree square field of view (32K×32K pixels). ODI will utilize high resistivity, red sensitive, orthogonal transfer (OT) CCDs to provide rapid correction for image motion arising from telescope shake, guider errors, and atmospheric effects. ODI will correct the full field of view by deploying 64 array packages having a total of 4096 independently controllable OTCCDs that can correct individually for local (2 arcmin) image motion. Each array package is an orthogonal transfer array (OTA) of 64 CCDs arranged in an 8×8 grid. Each CCD has 512×512 pixels. We expect the median image quality at the WIYN 3.5m telescope in RIZ to be 0.52”, 0.43”, and 0.35” FWHM. ODI makes optimal use of the WIYN telescope, which has superb optics, excellent seeing characteristics, a natural 1.4 degree field of view (with a new corrector), and can serve as a pathfinder for LSST in terms of detectors, data pipelines, operations strategies, and scientific motivation.
TL;DR: In this paper, the authors describe progress in removing image motion over large fields of view using a camera using a new type of CCD and report first results which are very promising for wide field imaging.
Abstract: We describe progress in removing image motion over large fields of view. A camera using a new type of CCD has been commissioned and we report first results which are very promising for wide field imaging. We are embarking on a project to build a new type of astronomical CCD which should provide image motion compensation over arbitrarily large fields of view, very fast readout, autoguiding capability, good red sensitivity, and should be significantly less expensive than the present generation of CCDs.
TL;DR: The spectral reduction pipeline for the Sloan Digital Sky Survey (SDSS) is described in this paper, where the authors give an overview of the workings of the pipeline and its outputs and give some guidance in using those outputs.
Abstract: The Sloan Digital Sky Survey(SDSS) is a redshift factory producing more than 5000 spectra a night when conditions allow. In order not to fall behind the data acquisition, highly automated and accurate spectral reduction pipelines are needed to process the data. Also the varied nature of SDSS target selection: the main galaxy sample, the large red galaxy sample, the QSO sample, stellar targets, and serendipitous objects; requires the pipeline to be adept at handling the full range of astronomical spectra, from a redshift of 0 out to a redshift of 6. The SDSS spectra are of exceptionally high quality, allowing the pipeline not only to determine redshifts and broadly classify the spectra, but also measure line parameters, calculate spectral indices, velocity dispersions etc. The purpose of this summary is to give an overview of the workings of the pipeline and its outputs, and give some guidance in using those outputs.
TL;DR: A preliminary assess-ment shows that the beam combining problem is the most challenging aspect of sparse optical arrays, and the wavefront sensing/control requirements appear to be a major technology and cost driver.
Abstract: In order to better understand the technological difficulties involved in designing and building a sparse aperture array, the challenge of building a white light Golay-3 telescope was undertaken. The MIT Adaptive Reconnaissance Golay-3 Optical Satellite (ARGOS) project exploits wide-angle Fizeau interferometer technology with an emphasis on modularity in the optics and spacecraft subsystems. Unique design procedures encompassing the nature of coherent wavefront sensing, control and combining as well as various system engineering aspects to achieve cost effectiveness, are developed. To demonstrate a complete spacecraft in a 1-g environment, the ARGOS system is mounted on a frictionless air-bearing, and has the ability to track fast orbiting satellites like the ISS or the planets. Wavefront sensing techniques are explored to mitigate initial misalignment and to feed back real-time aberrations into the optical control loop. This paper presents the results and the lessons learned from the conceive, design and implementation phases of ARGOS. A preliminary assess-ment shows that the beam combining problem is the most challenging aspect of sparse optical arrays. The need for optical control is paramount due to tight beam combining tolerances. The wavefront sensing/control requirements appear to be a major technology and cost driver.
TL;DR: In this article, a 6-inch stretched membrane mirror prototype was developed and tested using electrostatic pressure to pull the nominally flat mirror to a 32 m radius of curvature and adjust for aberrations.
Abstract: Exploration of faint distant objects in space has been limited by the power of telescopes. Currently our only option for studying these remote objects is to build larger and better telescopes. These giant telescopes are often constrained by system mass, which is dominated by the primary mirror. It appears that the evolutionary path of using conventional technology to build giant mirrors will not be sufficient to meet the small areal density of approximately 1.5 kg/m 2 . Therefore the development of large primary mirrors for space is dependent on innovative approaches and new technology. One approach to building a large primary reflector is to use smaller individual segments and place them along a curve approximating a paraboloid. These smaller segments could be comprised of either flat or curved thin membrane mirrors. These thin membrane mirrors have the potential of meeting the small areal density requirement.
We have started development on a thin membrane mirror. We have built and are testing a 6 inch stretched membrane mirror prototype that uses electrostatic pressure to pull the nominally flat mirror to a 32 m radius of curvature and adaptively correct for aberrations. Preliminary test results of the flat membrane are promising. The surface error for the flat membrane was measured to better than λ/10 rms for the center four inches and λ/20 rms over the central three inches. The interferograms for the curved membrane show a residual figure-eight pattern of high order astigmatism, most likely due to tension anisotropy in the mirror. Analysis on the fully curved mirror is still on-going. This paper discusses the SMEC design, development, test results, and current on-going activities.
TL;DR: This paper presents some of the main aspects of the software library that has been developed for the reduction of optical and infrared images, an integral part of the end-to-end survey system being built to support public imaging surveys at ESO.
Abstract: Newalgorithmsandtechnologiesfortheun-sup ervisedreductionofOptical/IRimagesBenoit VandameEurop ean Southern Observatory, Karl-Schwarzchild-Str. 2, D-85748 Garching b ei Munchen, Germany.ABSTRACTThis pap er presents some of the main asp ects of the software library that has b een develop ed for the reductionof optical and infrared images, an integral part of the end-to-end survey system b eing built to supp ort publicimaging surveys at ESO. Some of the highlights of the new library are:unbiased estimates of the background,critical for deep IR observations; e cient and accurate astrometric solutions, using multi-resolution techniques;automatic identi cation and masking of satellite tracks; weighted co-addition of images; creation of optical/IRmosaics, and appropriate managementof multi-chip instruments.These various elements have b een integratedintoasystemusingXMLtechnologyforsettinginputparameters,drivingthevariouspro cesses,pro ducingcomprehensive history logs and storing the results, binding them to the supp orting database and to the web.Thesystemhas b eenextensivelytestedusing deepimagesas wellas images ofcrowded elds(e.g.,globularclusters, LMC), pro cessing at a rate of 0.5 Mega-pixels p er second using a DS20E ALPHA computer with twopro cessors.Thegoalofthis presentation is to review some of the main features of this package.Keywords:Image Pro cessing, Astrometry Registration, Fringes, XML.1. INTRODUCTIONTheESOImaging Survey (EIS)3pro ject atis an ongoing eort to conductpublic imaging surveys andto develop the required infrastructure and software to ols to supp ort the large volume of optical/infrared dataexp ected from suchsurveys, using dedicated imaging telescop es such as VST and VISTA.Since 1997 EIS10has conducted a variety of medium-size optical/infrared surveys.The challenge has b eento cop e with the variety of imagers and observing strategies and, more recently, with the large volume of datacomingfromthewide- eldimager(WFI)mountedon2.2mtelescop eatLaSilla.Inearlyphasesof thispro ject the main eortwas to adapt existing softare to the pro ject's particular needsleading to theuseofdierentpackages(e.g.,IRAF,ECLIPSE).Thismadeitdi culttodevelopacommonenvironmenfor op erations.Therefore, forthe pasttwoyears aneort has b eenmadetodevelop a common,end-to-end,integratedsystemcapableofsupp ortingun-sup ervisedreduction.FromtheEISsurvey systemitisp ossibletoprepareobservations,retrieverawdataandconvertthesesciencegradepro ductsintheformoffullycalibrated pixel maps,catalogs and other derived pro ducts6.Thiseort has progressed in several fronts andincludesthedevelopmentofanadministrativewrapp erusingPython,graphicuserinterfaces(Tcl/Tk),integration of a supp orting database (Sybase), a suite of survey to ols and an image pro cessing package.Coping with the large volume of data exp ected in the future, and the multi-wavelength nature of the publicimagingsurveys currentlybeingconductedrequirestheimagereductionsoftware tohaveahigh-throughputand to b e instrument-indep endent.This has b een accomplished using a new, C-based library whichintegratesXML technology and a host of new algorithms to deal with a variety of situations encountered in observationscovering the optical and infrared domains, while using single- and multi-chip instruments.Here a brief reviewof the main concepts and algorithms is presented.
TL;DR: A new camera controller system called ArcVIEW is developed to meet the needs of the SOAR 4.2-m telescope first-generation instrument suite, as well as new instruments for the Blanco 4- m telescope, using National Instrument's LabVIEW environment.
Abstract: To meet the needs of the SOAR 4.2-m telescope first-generation instrument suite, as well as new instruments for the Blanco 4-m telescope, we developed a new camera controller system called ArcVIEW. In order to provide a strong foundation and rapid development cycle, we decided to build the system using National Instrument's LabVIEW environment. The advantages of this approach centers on the tools available for rapid prototyping, integration and testing of components.
Over the past 2 years, we have taken ArcVIEW from a design document to the point of controlling two new instruments being built at CTIO. The IR imager, ISPI, will complete final testing this semester and go into use on the Blanco telescope in September 2002.
The second instrument, the SOAR Optical Imager, is due for completion this semester and will be the commissioning instrument for the SOAR telescope, for which first light is expected in early 2003.
TL;DR: The architecture of ACS is presented and its status, detailing the object model and major services, and it is shown how ACS can be used in other new control systems, since it implements proven design patterns using state of the art, stable and reliable technology.
Abstract: The Atacama Large Millimeter Array (ALMA) is a joint project between astronomical organizations in Europe and North America. ALMA will consist of at least 64 12-meter antennas operating in the millimeter and sub-millimeter range, with baselines up to 14 km. It will be located at an altitude above 5000m in the Chilean Atacama desert.
The ALMA Common Software (ACS) provides a software infrastructure common to all partners and consists of a documented collection of common patterns and of components that implement those patterns.
The heart of ACS is an object model based on Distributed Objects (DOs), implemented as CORBA objects. The teams responsible for the control system development use DOs as the basis for components and devices such as an antenna mount control.
ACS provides common CORBA-based services such as logging, error and alarm management, configuration database and lifecycle management. A code generator creates a Java Bean for each DO. Programmers can write Java client applications by connecting those Beans with data-manipulation and visualization Beans.
ACS is based on the experience gained in the astronomical and particle accelerator domains, and reuses and extends proven concepts and components. Although designed for ALMA, ACS can be used in other new control systems, since it implements proven design patterns using state of the art, stable and reliable technology.
This paper presents the architecture of ACS and its status, detailing the object model and major services.
Abstract: The baseline design for the Large Synoptic Survey Telescope (LSST) requires a detector mosaic of over 2 Gigapixels covering a 55 cm diameter focal plane with 0.2 arcsec sampling. The camera and detector package for this telescope will benefit greatly by utilizing advanced concepts not normally required for astronomical telescope instrumentation. For the detector assembly, these concepts include low-cost, back illuminated CMOS or CCDs detectors with integrated electronic modules, curved detectors which would allow fewer but larger individual sensors, small pixels which maintain high MTF and full well capacity, anti-blooming techniques, fully-buttable packaging, and near room temperature operation. The camera may require a low thermal conductance gas-filled dewar to reduce atmosphere loading on the window, interchangeable and compact optical filters, and a flexible internal shutter. In this paper we discuss these issues relating to LSST focal plane technology.
TL;DR: This factory produced data for the SDSS Early Data Release in June 2001, and it is currently producing Data Release One, scheduled for January 2003, by chaining these pipelines together while using an operational database to hold processed imaging catalogs.
Abstract: The Sloan Digital Sky Survey (SDSS) data handling presents two challenges: large data volume and timely production of spectroscopic plates from imaging data. A data processing factory, using technologies both old and new, handles this flow. Distribution to end users is via disk farms, to serve corrected images and calibrated spectra, and a database, to efficiently process catalog queries.
For distribution of modest amounts of data from Apache Point Observatory to Fermilab, scripts use rsync to update files, while larger data transfers are accomplished by shipping magnetic tapes commercially. All data processing pipelines are wrapped in scripts to address consecutive phases: preparation, submission, checking, and quality control. We constructed the factory by chaining these pipelines together while using an operational database to hold processed imaging catalogs. The science database catalogs all imaging and spectroscopic object, with pointers to the various external files associated with them.
Diverse computing systems address particular processing phases. UNIX computers handle tape reading and writing, as well as calibration steps that require access to a large amount of data with relatively modest computational demands. Commodity CPUs process steps that require access to a limited amount of data with more demanding computations requirements. Disk servers optimized for cost per Gbyte serve terabytes of processed data, while servers optimized for disk read speed run SQLServer software to process queries on the catalogs.
This factory produced data for the SDSS Early Data Release in June 2001, and it is currently producing Data Release One, scheduled for January 2003.
TL;DR: The LSST as discussed by the authors is a three-mirror telescope with an 8.4 m concave primary, a 3.4m convex secondary and a 5.2m concave tertiary in a Paul geometry.
Abstract: This paper presents an improved optical design for the LSST, an f/1.25 three-mirror telescope covering 3.0 degrees full field angle, with 6.9 m effective aperture diameter. The telescope operates at five wavelength bands spanning 386.5 nm to 1040 nm (B, V, R, I and Z). For all bands, 80% of the polychromatic diffracted energy is collected within 0.20 arc-seconds diameter. The reflective telescope uses an 8.4 m f/1.06 concave primary, a 3.4 m convex secondary and a 5.2 m concave tertiary in a Paul geometry. The system length is 9.2 m. A refractive corrector near the detector uses three fused silica lenses, rather than the two lenses of previous designs. Earlier designs required that one element be a vacuum barrier, but now the detector sits in an inert gas at ambient pressure, with the last lens serving as the gas barrier. Small adjustments lead to optimal correction at each band. Each filter has a different axial thickness, and the primary and tertiary mirrors are repositioned for each wavelength band. Features that simplify manufacturing include a flat detector, a far less aspheric convex secondary (10 μm from best fit sphere) and reduced aspheric departures on the lenses and tertiary mirror. Five aspheric surfaces, on all three mirrors and on two lenses, are used. The primary is nearly parabolic. The telescope is fully baffled so that no specularly reflected light from any field angle, inside or outside of the full field angle of 3.0 degrees, can reach the detector.
TL;DR: The VISTA (Visible and Infrared Survey Telescope for Astronomy) project as discussed by the authors was the first one to use a VISTA camera with a 1.65 degrees diameter field of view.
Abstract: We give an overview of the current status of the VISTA (Visible and Infrared Survey Telescope for Astronomy) project to build a 4-m wide field survey telescope to be operated by ESO (the European Southern Observatory) at the Cerro Paranal Observatory in Chile. First light in 2006 will be with the Infrared (J, H, Ks) Camera with a 1.65 degrees diameter field of view able to accommodate sixteen 2k × 2k IR detectors with 0.34''pixel size. Some motivations driving the choice of site, current design, and operational mode are discussed. We outline some innovative features of the system, which were necessary to deal with, or arose from, the very large field of view, including a cold baffle (rather than cold stop) in the IR camera, lack of traditional telescope focus, f/1 primary mirror, thermal control of the IR camera etc. These are cross-referenced to more detailed analyses by members of the VISTA Project Office team presented at this meeting. Estimated IR performance for VISTA is given. The scientific gains from adding the 2.1 degrees field of view Visible Camera when funds become available are stressed. The problems of processing 0.4TB of survey data acquired each night are discussed.
TL;DR: CMOS-based Imaging system-on-chip (i-SoC) technology is successfully producing large monolithic and hybrid FPAs that are superior in many respects to competing CCD-based imaging sensors.
Abstract: CMOS-based imaging system-on-chip (i-SoC) technology is successfully producing large monolithic and hybrid FPAs that are superior in many respects to competing CCD-based imaging sensors. The hybrid approach produces visible 2048 by 2048 FPAs with <6 e- read noise and quantum efficiency above 80% from 400 nm to 920 nm; 4096 by 4096 mosaics are now being developed. The monolithic approach produces visible 12-bit imaging system-on-chips such as a 1936 by 1088 with higher quantum efficiency than mainstream CCDs, <25 e- read noise, <0.02% fixed pattern noise, automatic identification and replacement of defective pixels, black-level clamping, total power dissipation of only 180 mW, and various programmable features. Several successors having ≥12 Mpixels are in development. In both cases low-light-level performance is boosted by coupling the sensors to image intensifiers.