A. Rasmussen

Netherlands Institute for Space Research, Utrecht, Utrecht, Utrecht, Netherlands

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Publications (90)84.2 Total impact

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    Andrew Rasmussen
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    ABSTRACT: We build on previous efforts to model CCD sensors, during illumination and collection of conversions. We use a finite summation of simple, electrostatic field models. The upgraded functionality of our framework provides specific predictions for perturbations in pixel boundary enclosures (e.g., at the backside window) and the bookkeeping capability to stack those perturbations so that they may be utilized as Greens functions -- portable calculation results that may be generically applied to a range of precision astronomy related problems that naturally including astrometric, photometric and shape transfer issues. We approach the topic of using ancillary pixel data, derived from the Greens function and the registered image, to analyze sky data and constrain object parameters of astronomical targets.
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    ABSTRACT: The LSST Camera science sensor array will incorporate 189 large format Charge Coupled Device (CCD) image sensors. Each CCD will include over 16 million pixels and will be divided into 16 equally sized segments and each segment will be read through a separate output amplifier. The science goals of the project require CCD sensors with state of the art performance in many aspects. The broad survey wavelength coverage requires fully depleted, 100 micrometer thick, high resistivity, bulk silicon as the imager substrate. Image quality requirements place strict limits on the image degradation that may be caused by sensor effects: optical, electronic, and mechanical. In this paper we discuss the design of the prototype sensors, the hardware and software that has been used to perform electro-optic testing of the sensors, and a selection of the results of the testing to date. The architectural features that lead to internal electrostatic fields, the various effects on charge collection and transport that are caused by them, including charge diffusion and redistribution, effects on delivered PSF, and potential impacts on delivered science data quality are addressed.
    SPIE Astronomical Telescopes + Instrumentation; 08/2014
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    ABSTRACT: The LSST will, over a 10-year period, produce a multi-color, multi-epoch survey of more than 18000 square degrees of the southern sky. It will generate a multi-petabyte archive of images and catalogs of astrophysical sources from which a wide variety of high-precision statistical studies can be undertaken. To accomplish these goals, the LSST project has developed a suite of modeling and simulation tools for use in validating that the design and the as-delivered components of the LSST system will yield data products with the required statistical properties. In this paper we describe the development, and use of the LSST simulation framework, including the generation of simulated catalogs and images for targeted trade studies, simulations of the observing cadence of the LSST, the creation of large-scale simulations that test the procedures for data calibration, and use of end-to-end image simulations to evaluate the performance of the system as a whole.
    SPIE Astronomical Telescopes + Instrumentation; 08/2014
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    ABSTRACT: Near-future astronomical survey experiments, such as LSST, possess system requirements of unprecedented fidelity that span photometry, astrometry and shape transfer. Some of these requirements flow directly to the array of science imaging sensors at the focal plane. Availability of high quality characterization data acquired in the course of our sensor development program has given us an opportunity to develop and test a framework for simulation and modeling that is based on a limited set of physical and geometric effects. In this paper we describe those models, provide quantitative comparisons between data and modeled response, and extrapolate the response model to predict imaging array response to astronomical exposure. The emergent picture departs from the notion of a fixed, rectilinear grid that maps photo-conversions to the potential well of the channel. In place of that, we have a situation where structures from device fabrication, local silicon bulk resistivity variations and photo-converted carrier patterns still accumulating at the channel, together influence and distort positions within the photosensitive volume that map to pixel boundaries. Strategies for efficient extraction of modeling parameters from routinely acquired characterization data are described. Methods for high fidelity illumination/image distribution parameter retrieval, in the presence of such distortions, are also discussed.
    Proceedings of SPIE - The International Society for Optical Engineering 07/2014; DOI:10.1117/12.2057411 · 0.20 Impact Factor
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    Andrew Rasmussen
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    ABSTRACT: We describe the drift field in thick depleted silicon sensors as a superposition of a one-dimensional backdrop field and various three-dimensional perturbative contributions that are physically motivated. We compute trajectories for the conversions along the field lines toward the channel and into volumes where conversions are confined by the perturbative fields. We validate this approach by comparing predictions against measured response distributions seen in five types of fixed pattern distortion features. We derive a quantitative connection between "tree ring" flat field distortions to astrometric and shape transfer errors with connections to measurable wavelength dependence - as ancillary pixel data that may be used in pipeline analysis for catalog population. Such corrections may be tested on DECam data, where correlations between tree ring flat field distortions and astrometric errors - together with their band dependence - are already under study. Dynamic effects, including the brighter-fatter phenomenon for point sources and the flux dependence of flat field fixed pattern features are approached using perturbations similar in form to those giving rise to the fixed pattern features. These in turn provide drift coefficient predictions that can be validated in a straightforward manner. Once the three parameters of the model are constrained using available data, the model is readily used to provide predictions for arbitrary photo-distributions with internally consistent wavelength dependence provided for free.
    Journal of Instrumentation 03/2014; 9(04). DOI:10.1088/1748-0221/9/04/C04027 · 1.53 Impact Factor
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    ABSTRACT: This white paper describes the LSST Dark Energy Science Collaboration (DESC), whose goal is the study of dark energy and related topics in fundamental physics with data from the Large Synoptic Survey Telescope (LSST). It provides an overview of dark energy science and describes the current and anticipated state of the field. It makes the case for the DESC by laying out a robust analytical framework for dark energy science that has been defined by its members and the comprehensive three-year work plan they have developed for implementing that framework. The analysis working groups cover five key probes of dark energy: weak lensing, large scale structure, galaxy clusters, Type Ia supernovae, and strong lensing. The computing working groups span cosmological simulations, galaxy catalogs, photon simulations and a systematic software and computational framework for LSST dark energy data analysis. The technical working groups make the connection between dark energy science and the LSST system. The working groups have close linkages, especially through the use of the photon simulations to study the impact of instrument design and survey strategy on analysis methodology and cosmological parameter estimation. The white paper describes several high priority tasks identified by each of the 16 working groups. Over the next three years these tasks will help prepare for LSST analysis, make synergistic connections with ongoing cosmological surveys and provide the dark energy community with state of the art analysis tools. Members of the community are invited to join the LSST DESC, according to the membership policies described in the white paper. Applications to sign up for associate membership may be made by submitting the Web form at http://www.slac.stanford.edu/exp/lsst/desc/signup.html with a short statement of the work they wish to pursue that is relevant to the LSST DESC.
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    ABSTRACT: The design of the Large Synoptic Survey Telescope (LSST) requires a camera system of unprecedented size and complexity. Achieving the science goals of the LSST project, through design, fabrication, integration, and operation, requires a thorough understanding of the camera performance. Essential to this effort is the camera modeling which defines the effects of a large number of potential mechanical, optical, electronic or sensor variations which can only be captured with sophisticated instrument modeling that incorporates all of the crucial parameters. This paper presents the ongoing development of LSST camera instrument modeling and details the parametric issues and attendant analysis involved with this modeling.
    Proceedings of SPIE - The International Society for Optical Engineering 09/2012; DOI:10.1117/12.926611 · 0.20 Impact Factor
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    ABSTRACT: The precise measurements planned for the Large Synoptic Survey Telescope (LSST) require careful algorithmic studies before the telescope begins operating with its unprecedented image production rate. The LSST Image Simulation group is leading the effort to simulate the LSST system from end-to-end using a high fidelity framework. We first synthesize input astrophysical object catalogs that include stars based on a galaxy model, asteroids, and cosmologically-based galaxy catalogs with morphological parameters. We then use a novel approach to simulate images using a photon Monte Carlo approach. We draw photons from the objects using their spectral energy distributions and propagate those photons through the Universe, atmosphere, telescope, and camera using complex wavelength-dependent photon simulation physics. We describe the simulation framework, and discuss the photon simulation approach that has been used generate millions of high fidelity images.
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    ABSTRACT: ORIGIN is a proposal for the M3 mission call of ESA aimed at the study of metal creation from the epoch of cosmic dawn. Using high-spectral resolution in the soft X-ray band, ORIGIN will be able to identify the physical conditions of all abundant elements between C and Ni to red-shifts of z=10, and beyond. The mission will answer questions such as: When were the first metals created? How does the cosmic metal content evolve? Where do most of the metals reside in the Universe? What is the role of metals in structure formation and evolution? To reach out to the early Universe ORIGIN will use Gamma-Ray Bursts (GRBs) to study their local environments in their host galaxies. This requires the capability to slew the satellite in less than a minute to the GRB location. By studying the chemical composition and properties of clusters of galaxies we can extend the range of exploration to lower redshifts (z ~ 0.2). For this task we need a high-resolution spectral imaging instrument with a large field of view. Using the same instrument, we can also study the so far only partially detected baryons in the Warm-Hot Intergalactic Medium (WHIM). The less dense part of the WHIM will be studied using absorption lines at low redshift in the spectra for GRBs.
    Experimental Astronomy 04/2011; 34(2):519. · 2.66 Impact Factor
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    ABSTRACT: The Large Synoptic Survey Telescope (LSST) uses a novel, three-mirror, modified Paul-Baker design, with an 8.4-meter primary mirror, a 3.4-m secondary, and a 5.0-m tertiary feeding a refractive camera design with 3 lenses (0.69-1.55m) and a set of broadband filters/corrector lenses. Performance is excellent over a 9.6 square degree field and ultraviolet to near infrared wavelengths. We describe the image quality error budget analysis methodology which includes effects from optical and optomechanical considerations such as index inhomogeneity, fabrication and null-testing error, temperature gradients, gravity, pressure, stress, birefringence, and vibration.
    Proceedings of SPIE - The International Society for Optical Engineering 07/2010; DOI:10.1117/12.857682 · 0.20 Impact Factor
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    ABSTRACT: Optically fed by LSST's fast and wide-field optics, the camera has a 9.6 square degree FOV in a 3.2 Gigapixel focal plane array. The focal plane is tiled by 189 4Kx4K CCD science sensors with 10μm (0.2 arcsec) pixels and also houses four diagnostic ("corner raft") packages that provide guide- and wavefront-sensors at opposing sides of the field. The focal plane array is highly modular and features a parallelized readout scheme, allowing the entire array to be read in 2 seconds. Dedicated front- and back-end electronics boards housed within the cryostat vacuum vessel operate sensors in raft groups (3x3 sensors; 144 data channels) while mechanically identical "rafts” are precision-mounted on a rigid silicon carbide grid structure. Three large, refractive lens elements act as the optical system's corrector (the third, L3, provides the vacuum barrier for the cryostat), and one of six possible band-pass filters is positioned in the beam at any given time. Mechanisms within the camera include a mechanical shutter and a carousel filter changer assembly. The camera control system manages all aspects of camera operation including image capture, thermal monitoring and control, vacuum control, filter changes, and communication with the observatory control system. The data acquisition system records and pre-processes raw images, provides up to 3 days of storage capacity, and provides very high throughput data transfer to downstream data management.
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    ABSTRACT: A survey that can cover the sky in optical bands over wide fields to faint magnitudes with a fast cadence will enable many of the exciting science opportunities of the next decade. The Large Synoptic Survey Telescope (LSST) will have an effective aperture of 6.7 meters and an imaging camera with field of view of 9.6 deg^2, and will be devoted to a ten-year imaging survey over 20,000 deg^2 south of +15 deg. Each pointing will be imaged 2000 times with fifteen second exposures in six broad bands from 0.35 to 1.1 microns, to a total point-source depth of r~27.5. The LSST Science Book describes the basic parameters of the LSST hardware, software, and observing plans. The book discusses educational and outreach opportunities, then goes on to describe a broad range of science that LSST will revolutionize: mapping the inner and outer Solar System, stellar populations in the Milky Way and nearby galaxies, the structure of the Milky Way disk and halo and other objects in the Local Volume, transient and variable objects both at low and high redshift, and the properties of normal and active galaxies at low and high redshift. It then turns to far-field cosmological topics, exploring properties of supernovae to z~1, strong and weak lensing, the large-scale distribution of galaxies and baryon oscillations, and how these different probes may be combined to constrain cosmological models and the physics of dark energy.
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    ABSTRACT: How structures of various scales formed and evolved from the early Universe up to present time is a fundamental question of astrophysical cosmology. EDGE (Piro et al., 2007) will trace the cosmic history of the baryons from the early generations of massive stars by Gamma-Ray Burst (GRB) explosions, through the period of galaxy cluster formation, down to the very low redshift Universe, when between a third and one half of the baryons are expected to reside in cosmic filaments undergoing gravitational collapse by dark matter (the so-called warm hot intragalactic medium). In addition EDGE, with its unprecedented capabilities, will provide key results in many important fields. These scientific goals are feasible with a medium class mission using existing technology combined with innovative instrumental and observational capabilities by: (a) observing with fast reaction Gamma-Ray Bursts with a high spectral resolution. This enables the study of their star-forming and host galaxy environments and the use of GRBs as back lights of large scale cosmological structures; (b) observing and surveying extended sources (galaxy clusters, WHIM) with high sensitivity using two wide field of view X-ray telescopes (one with a high angular resolution and the other with a high spectral resolution). The mission concept includes four main instruments: a Wide-field Spectrometer (0.1-2.2 eV) with excellent energy resolution (3 eV at 0.6 keV), a Wide-Field Imager (0.3-6 keV) with high angular resolution (HPD = 15") constant over the full 1.4 degree field of view, and a Wide Field Monitor (8-200 keV) with a FOV of A1/4 of the sky, which will trigger the fast repointing to the GRB. Extension of its energy response up to 1 MeV will be achieved with a GRB detector with no imaging capability. This mission is proposed to ESA as part of the Cosmic Vision call. We will outline the science drivers and describe in more detail the payload of this mission.
    Experimental Astronomy 03/2009; 23(1):67. DOI:10.1007/s10686-008-9092-y · 2.66 Impact Factor
  • astro2010: The Astronomy and Astrophysics Decadal Survey; 01/2009
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    ABSTRACT: A long 280 ks observation of the Seyfert 1 galaxy NGC 3783 with XMM-Newton is reported. We focus on the oxygen line complex between 17 and 24 Å as measured with the Reflection Grating Spectrometer. Accurate absorption column densities and emission-line fluxes are obtained. We explore several options for the geometry and physical form of the emitting and absorbing gas. The lack of change in ionization in the absorber despite an increase in continuum flux during the observation restricts the high-ionization (O-K) and the low-ionization (Fe-M) gas to distances of at least 0.5 and 2.8 pc, respectively, away from the central source. Given the P Cygni type profiles in the resonance spectral lines and the similar velocity widths, column densities, and ionization structure inferred separately from the emission and absorption lines, it is tempting to relate the X-ray narrow-line emitting plasma with the X-ray-absorbing gas. Under this assumption, the scenario of dense clumped clouds can be ruled out. Conversely, extended ionization cones (r 10 pc) are consistent with the observation independent of this assumption. These findings are in stark contrast to the picture of numerous clumpy (ne 109 cm-3) clouds drawn recently from UV spectra, but they are consistent with the extended X-ray emission cones observed directly in Seyfert 2 galaxies.
    The Astrophysical Journal 12/2008; 598(1):232. DOI:10.1086/378853 · 6.28 Impact Factor
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    ABSTRACT: We describe the most ambitious survey currently planned in the visible band, the Large Synoptic Survey Telescope (LSST). The LSST design is driven by four main science themes: probing dark energy and dark matter, taking an inventory of the Solar System, exploring the transient optical sky, and mapping the Milky Way. LSST will be a large, wide-field ground-based system designed to obtain multiple images covering the sky that is visible from Cerro Pachon in Northern Chile. The current baseline design, with an 8.4m (6.5m effective) primary mirror, a 9.6 sq. deg. field of view, and a 3.2 Gigapixel camera, will allow about 10,000 sq.deg. of sky to be covered using pairs of 15-second exposures twice per night every three nights on average, with typical 5-sigma depth for point sources of r=24.5. The system is designed to yield high image quality as well as superb astrometric and photometric accuracy. The total survey area will include 30,000 sq.deg. with delta<+34.5, and will be imaged multiple times in six bands, ugrizy, covering the wavelength range 320-1050 nm. The project is scheduled to begin the regular survey operations before the end of this decade. About 90% of the observing time will be devoted to a deep-wide-fast survey mode which will uniformly observe a 18,000 sq.deg. region about 1000 times (summed over all six bands) during the anticipated 10 years of operations, and yield a coadded map to r=27.5. These data will result in databases including 10 billion galaxies and a similar number of stars, and will serve the majority of science programs. (abridged)
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    ABSTRACT: In a series of papers, Nicastro et al. have reported the detection of z > 0 O VII absorption features in the spectrum of Mrk 421 obtained with the Chandra Low Energy Transmission Grating Spectrometer (LETGS). We evaluate this result in the context of a high-quality spectrum of the same source obtained with the Reflection Grating Spectrometer (RGS) on XMM-Newton. The data comprise over 955 ks of usable exposure time and more than 2.6 × 104 counts per 50 mÅ at 21.6 Å. We concentrate on the spectrally clean region (21.3 < λ < 22.5 ), where sharp features due to the astrophysically abundant O VII may reveal an intervening, warm-hot intergalactic medium (WHIM). We do not confirm detection of any of the intervening systems claimed to date. Rather, we detect only three unsurprising, astrophysically expected features down to the log(Ni) ~ 14.6 (3 σ) sensitivity level. Each of the two purported WHIM features is rejected with a statistical confidence that exceeds that reported for its initial detection. While we cannot rule out the existence of fainter, WHIM related features in these spectra, we suggest that previous discovery claims were premature. A more recent paper by Williams et al. claims to have demonstrated that the RGS data we analyze here do not have the resolution or statistical quality required to confirm or deny the LETGS detections. We show that our analysis resolves the issues encountered by Williams et al. and recovers the full resolution and statistical quality of the RGS data. We highlight the differences between our analysis and those published by Williams et al. as this may explain our disparate conclusions.
    The Astrophysical Journal 02/2007; DOI:10.2172/881779 · 6.28 Impact Factor
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    ABSTRACT: We present extragalactic research plans that are developing for the LSST sky survey. The LSST Galaxies Science Collaboration team is a working group with several goals. One goal is to identify science use cases for the enormous LSST survey data archive and database that either stretch the capabilities of the system or else are missing from current LSST science use case scenarios. In addition, the team is working to identify gaps in other current, on-going, or planned non-LSST sky surveys, in order to develop the LSST science case for those research problems. The team is also investigating what precursor extragalactic studies need to be addressed and which data sets are missing now but which need to be available in order for LSST galaxies research to reach its full potential when the facility begins operations. Finally, the team is working with the LSST Data Management team to verify that the expected science database queries for extragalactic science are represented and doable within the LSST database schema. We will present our initial findings, general research themes, and potential synergies with other LSST Science Collaborations and other Sky Survey projects.
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    ABSTRACT: We present a spectrometer design based on a novel nanofabricated blazed X-ray transmission grating which is modeled to have superior efficiency. Here we outline a full instrument design proposed for Constellation-X which is expected to give resolving powers ~2000 (HEW). The spectrometer advantages include lower mass budget and smaller diffractor area, as well as order-of-magnitude more relaxed alignment tolerances for crucial degrees of freedom than reflection grating schemes considered in the past1,2,3. The spectrometer readout is based on conventional CCD technology adapted to operate with very high speed and low power. This instrument will enable high resolution absorption and emission line spectroscopy in the critical band between 0.2 and 1.5 keV.
    Proceedings of SPIE - The International Society for Optical Engineering 01/2007; 6688. DOI:10.1117/12.739941 · 0.20 Impact Factor

Publication Stats

1k Citations
84.20 Total Impact Points

Institutions

  • 2011
    • Netherlands Institute for Space Research, Utrecht
      Utrecht, Utrecht, Netherlands
  • 2009
    • Lawrence Livermore National Laboratory
      Livermore, California, United States
  • 1996–2008
    • Columbia University
      • Columbia Astrophysics Laboratory
      New York City, NY, United States
  • 2006
    • Stanford University
      • Department of Physics
      Palo Alto, California, United States
    • Universiteit Utrecht
      • Astronomical Institute
      Utrecht, Utrecht, Netherlands