Showing papers by "Peter Nugent published in 2003"
Association of Universities for Research in Astronomy1, Vanderbilt University2, Lawrence Berkeley National Laboratory3, Stockholm University4, Pierre-and-Marie-Curie University5, Colorado College6, University of California, Berkeley7, American Astronomical Society8, University of Tokyo9, California Institute of Technology10, Instituto Superior Técnico11, Space Telescope Science Institute12, University of Oxford13, European Southern Observatory14, University of Barcelona15, École Polytechnique16, University of Texas at Austin17, Durham University18, University of Cambridge19
TL;DR: In this paper, a set of high-redshift supernovae were used to confirm previous supernova evidence for an accelerating universe, and the supernova results were combined with independent flat-universe measurements of the mass density from CMB and galaxy redshift distortion data, they provided a measurement of $w=-1.05^{+0.15}-0.09$ if w is assumed to be constant in time.
Abstract: We report measurements of $\Omega_M$, $\Omega_\Lambda$, and w from eleven supernovae at z=0.36-0.86 with high-quality lightcurves measured using WFPC-2 on the HST. This is an independent set of high-redshift supernovae that confirms previous supernova evidence for an accelerating Universe. Combined with earlier Supernova Cosmology Project data, the new supernovae yield a flat-universe measurement of the mass density $\Omega_M=0.25^{+0.07}_{-0.06}$ (statistical) $\pm0.04$ (identified systematics), or equivalently, a cosmological constant of $\Omega_\Lambda=0.75^{+0.06}_{-0.07}$ (statistical) $\pm0.04$ (identified systematics). When the supernova results are combined with independent flat-universe measurements of $\Omega_M$ from CMB and galaxy redshift distortion data, they provide a measurement of $w=-1.05^{+0.15}_{-0.20}$ (statistical) $\pm0.09$ (identified systematic), if w is assumed to be constant in time. The new data offer greatly improved color measurements of the high-redshift supernovae, and hence improved host-galaxy extinction estimates. These extinction measurements show no anomalous negative E(B-V) at high redshift. The precision of the measurements is such that it is possible to perform a host-galaxy extinction correction directly for individual supernovae without any assumptions or priors on the parent E(B-V) distribution. Our cosmological fits using full extinction corrections confirm that dark energy is required with $P(\Omega_\Lambda>0)>0.99$, a result consistent with previous and current supernova analyses which rely upon the identification of a low-extinction subset or prior assumptions concerning the intrinsic extinction distribution.
1,687 citations
TL;DR: In this paper, a set of high-redshift supernovae were used to confirm previous supernova evidence for an accelerating universe, and the supernova results were combined with independent flat-universe measurements of the mass density from CMB and galaxy redshift distortion data, they provided a measurement of $w=-1.05^{+0.15}-0.09$ if w is assumed to be constant in time.
Abstract: We report measurements of $\Omega_M$, $\Omega_\Lambda$, and w from eleven supernovae at z=0.36-0.86 with high-quality lightcurves measured using WFPC-2 on the HST. This is an independent set of high-redshift supernovae that confirms previous supernova evidence for an accelerating Universe. Combined with earlier Supernova Cosmology Project data, the new supernovae yield a flat-universe measurement of the mass density $\Omega_M=0.25^{+0.07}_{-0.06}$ (statistical) $\pm0.04$ (identified systematics), or equivalently, a cosmological constant of $\Omega_\Lambda=0.75^{+0.06}_{-0.07}$ (statistical) $\pm0.04$ (identified systematics). When the supernova results are combined with independent flat-universe measurements of $\Omega_M$ from CMB and galaxy redshift distortion data, they provide a measurement of $w=-1.05^{+0.15}_{-0.20}$ (statistical) $\pm0.09$ (identified systematic), if w is assumed to be constant in time. The new data offer greatly improved color measurements of the high-redshift supernovae, and hence improved host-galaxy extinction estimates. These extinction measurements show no anomalous negative E(B-V) at high redshift. The precision of the measurements is such that it is possible to perform a host-galaxy extinction correction directly for individual supernovae without any assumptions or priors on the parent E(B-V) distribution. Our cosmological fits using full extinction corrections confirm that dark energy is required with $P(\Omega_\Lambda>0)>0.99$, a result consistent with previous and current supernova analyses which rely upon the identification of a low-extinction subset or prior assumptions concerning the intrinsic extinction distribution.
1,537 citations
TL;DR: In this article, a double-troughed absorption feature seen around 800 nm (FWHM about 22 nm) was identified for Type Ia supernova (SN Ia) 2001el with the ESO Very Large Telescope Melipal +FORS1 at five epochs.
Abstract: High-quality spectropolarimetry (range 417-860 nm; spectral resolution 1.27 nm and 0.265 nm pixel-1) of the Type Ia supernova (SN Ia) 2001el was obtained with the ESO Very Large Telescope Melipal (+FORS1) at five epochs. The spectra a week before maximum and around maximum indicate photospheric expansion velocities of about 10,000 km s-1. Prior to optical maximum, the linear polarization of the continuum was ≈0.2%-0.3% with a constant position angle, showing that SN 2001el has a well-defined axis of symmetry. The polarization was nearly undetectable a week after optical maximum. The spectra are similar to those of the normally bright SN 1994D, with the exception of a strong double-troughed absorption feature seen around 800 nm (FWHM about 22 nm). The 800 nm feature is probably due to the Ca II IR triplet at very high velocities (20,000-26,000 km s-1) involving ~0.004 M☉ of calcium and perhaps 0.1 M☉ total mass. The 800 nm feature is distinct in velocity space from the photospheric Ca II IR triplet and has a significantly higher degree of polarization (≈0.7%) and different polarization angle than the continuum. Taken together, these aspects suggest that this high-velocity calcium is a kinematically distinct feature with the matter distributed in a filament, torus, or array of "blobs" almost edge-on to the line of sight. This feature could thus be an important clue to the binary nature of SNe Ia, perhaps associated with an accretion disk, or to the nature of the thermonuclear burning, perhaps representing a stream of material ballistically ejected from the site of the deflagration to detonation transition. If modeled in terms of an oblate spheroid, the continuum polarization implies a minor to major axis ratio of around 0.9 if seen equator-on; this level of asymmetry would produce an absolute luminosity dispersion of about 0.1 mag when viewed at different viewing angles. If typical for SNe Ia, this would create an rms scatter of several hundredths of a magnitude around the mean brightness-decline relation. We discuss the possible implications of this scatter for the high-precision measurements required to determine the cosmological equation of state.
218 citations
TL;DR: In this article, the authors obtained high-quality spectropolarimetry (range 417-860 nm; spectral resolution 1.27 nm and 0.265 nm/pixel) of SN Ia 2001el with the ESO Very Large Telescope Melipal (+ FORS1) at 5 epochs.
Abstract: High-quality spectropolarimetry (range 417-860 nm; spectral resolution 1.27 nm and 0.265 nm/pixel) of the SN Ia 2001el were obtained with the ESO Very Large Telescope Melipal (+ FORS1) at 5 epochs. The spectra a week before maximum and around maximum indicate photospheric expansion velocities of about 10,000 km s$^{-1}$. Prior to optical maximum, the linear polarization of the continuum was $\approx 0.2 - 0.3 %$ with a constant position angle, showing that SN 2001el has a well-defined axis of symmetry. The polarization was nearly undetectable a week after optical maximum. The spectra are similar to those of the normally-bright SN 1994D with the exception of a strong double-troughed absorption feature seen around 800 nm (FWHM about 22 nm). This feature could be an important clue to the binary nature of SN Ia, perhaps associated with an accretion disk, or to the nature of the thermonuclear burning. If modeled in terms of an oblate spheroid, the continuum polarization implies a minor to major axis ratio of around 0.9 if seen equator-on; this level of asymmetry would produce an absolute luminosity dispersion of about 0.1 mag when viewed at different viewing angles. If typical for SNe Ia, this would create an RMS scatter of several hundredths of a magnitude around the mean brightness-decline relation.
204 citations
TL;DR: In this article, the authors used a three-dimensional synthetic polarization spectra to constrain the ejecta geometry and generate polarization profiles for several parameterized configurations of the supernova ejecta.
Abstract: SN 2001el is the first normal Type Ia supernova to show a strong, intrinsic polarization signal. In addition, during the epochs prior to maximum light, the Ca II IR triplet absorption is seen distinctly and separately at both normal photospheric velocities and at very high velocities. The high-velocity triplet absorption is highly polarized, with a different polarization angle than the rest of the spectrum. The unique observation allows us to construct a relatively detailed picture of the layered geometrical structure of the supernova ejecta: in our interpretation, the ejecta layers near the photosphere (v ? 10,000 km s-1) obey a nearly axial symmetry, while a detached, high-velocity structure (v ? 18,000-25,000 km s-1) with high Ca II line opacity deviates from the photospheric axisymmetry. By partially obscuring the underlying photosphere, the high-velocity structure causes a more incomplete cancellation of the polarization of the photospheric light and so gives rise to the polarization peak and rotated polarization angle of the high-velocity IR triplet feature. In an effort to constrain the ejecta geometry, we develop a technique for calculating three-dimensional synthetic polarization spectra and use it to generate polarization profiles for several parameterized configurations. In particular, we examine the case in which the inner ejecta layers are ellipsoidal and the outer, high-velocity structure is one of four possibilities: a spherical shell, an ellipsoidal shell, a clumped shell, or a toroid. The synthetic spectra rule out the spherical shell model, disfavor a toroid, and find a best fit with the clumped shell. We show further that different geometries can be more clearly discriminated if observations are obtained from several different lines of sight. Thus, assuming that the high-velocity structure observed for SN 2001el is a consistent feature of at least a known subset of Type Ia supernovae, future observations and analyses such as these may allow one to put strong constraints on the ejecta geometry and hence on supernova progenitors and explosion mechanisms.
162 citations
TL;DR: In this article, the authors constructed a relatively detailed picture of the layered geometrical structure of the supernova ejecta, showing that the ejecta layers near the photosphere obey a near axial symmetry, while a detached, high-velocity structure with high CaII line opacity deviates from the photospheric axisymmetry.
Abstract: SN 2001el is the first normal Type Ia supernova to show a strong, intrinsic polarization signal. In addition, during the epochs prior to maximum light, the CaII IR triplet absorption is seen distinctly and separately at both normal photospheric velocities and at very high velocities. The high-velocity triplet absorption is highly polarized, with a different polarization angle than the rest of the spectrum. The unique observation allows us to construct a relatively detailed picture of the layered geometrical structure of the supernova ejecta: in our interpretation, the ejecta layers near the photosphere (v \approx 10,000 km/s) obey a near axial symmetry, while a detached, high-velocity structure (v \approx 18,000-25,000 km/s) with high CaII line opacity deviates from the photospheric axisymmetry. By partially obscuring the underlying photosphere, the high-velocity structure causes a more incomplete cancellation of the polarization of the photospheric light, and so gives rise to the polarization peak and rotated polarization angle of the high-velocity IR triplet feature. In an effort to constrain the ejecta geometry, we develop a technique for calculating 3-D synthetic polarization spectra and use it to generate polarization profiles for several parameterized configurations. In particular, we examine the case where the inner ejecta layers are ellipsoidal and the outer, high-velocity structure is one of four possibilities: a spherical shell, an ellipsoidal shell, a clumped shell, or a toroid. The synthetic spectra rule out the spherical shell model, disfavor a toroid, and find a best fit with the clumped shell. We show further that different geometries can be more clearly discriminated if observations are obtained from several different lines of sight.
134 citations
Durham University1, California Institute of Technology2, Lawrence Berkeley National Laboratory3, Stockholm University4, Pierre-and-Marie-Curie University5, Colorado College6, University of California, Berkeley7, American Astronomical Society8, University of Tokyo9, Space Telescope Science Institute10, University of Oxford11, University of Cambridge12, Vanderbilt University13, European Southern Observatory14, University of Barcelona15, University of Texas at Austin16
TL;DR: In this article, the authors present new results on the Hubble diagram of distant type Ia supernovae (SNe Ia) segregated according to the type of host galaxy.
Abstract: We present new results on the Hubble diagram of distant type Ia supernovae (SNe Ia) segregated according to the type of host galaxy. This makes it possible to check earlier evidence for a cosmological constant by explicitly comparing SNe residing in galaxies likely to contain negligible dust with the larger sample. The cosmological parameters derived from these SNe Ia hosted by presumed dust-free early-type galaxies support earlier claims for a cosmological constant, which we demonstrate at �5σ significance, and the internal extinction implied is small even for late-type systems (AB < 0.2). Thus, our data demonstrate that host galaxy extinction is unlikely to systematically dim distant SNe Ia in a manner that would produce a spurious cosmological constant. Our analysis is based on new Hubble Space Telescope STIS ‘snapshot’ images and Keck-II echellette spectroscopy at the locations of the SNe, spanning the redshift range 0 < z < 0.8. Selecting from the sample discovered by the Supernova Cosmology Project (SCP), we classify the host galaxies of 39 distant SNe using the combination of STIS
122 citations
TL;DR: In this paper, the properties of low-redshift Type Ia supernovae were investigated using published multi-band optical broadband data from the Calan/Tololo and CfA surveys.
Abstract: The properties of low-redshift Type Ia supernovae are investigated using published multi-band optical broadband data from the Calan/Tololo and CfA surveys. The average time evolution of B − V, V − R, R − I, B − I and V − I, the intrinsic dispersion and time correlations are studied. This information is required to deduce the extinction of such explosions from the measured colours. We find that extinction corrections on individual SNe based on their colours up to 40 days past the B-band lightcurve maximum are generaly limited to σAV > 0.1, due to intrinsic variations, as far as it can be conservatively deduced with the current sample of data. However, we find that the V − R colour, especially at late times, is consistent with a negligible intrinsic spread, and may be the most accurate estimator for extinction.
41 citations
TL;DR: In this article, the properties of low-redshift Type Ia supernovae were investigated using published multi-band optical broadband data from the Calan/Tololo and CfA surveys.
Abstract: The properties of low-redshift Type Ia supernovae are investigated using published multi-band optical broadband data from the Calan/Tololo and CfA surveys. The average time evolution of B-V, V-R, R-I, B-I and V-I, the intrinsic dispersion and time correlations are studied. This information is required to deduce the extinction of such explosions from the measured colours. We find that extinction corrections on individual SNe based on their colours up to 40 days past the B-band lightcurve maximum are generaly limited to \sigma_{A_V} \gsim 0.1, due to intrinsic variations, as far as it can be conservatively deduced with the current sample of data. However, we find that the V-R colour, especially at late times, is consistent with a negligible intrinsic spread, and may be the most accurate estimator for extinction.
35 citations
TL;DR: In this article, a large grid of synthetic spectra was used to compare early spectroscopic observations of SN 1993W with the observed spectra of SN IIP and showed that very early spectra combined with detailed models can provide constraints on the value of the power law index, the ratio of hydrogen to helium in the surface of the progenitor and the amount of radioactive nickel mixed into the outer envelope of the supernova.
Abstract: We present the results of a large grid of synthetic spectra and compare them to early spectroscopic observations of SN 1993W. This supernova was discovered close to its explosion date and at a recession velocity of 5400 km/s is located in the Hubble flow. We focus here on two early spectra that were obtained approximately 5 and 9 days after explosion. We parameterize the outer supernova envelope as a power-law density profile in homologous expansion. In order to extract information on the value of the parameters a large number of models was required. We show that very early spectra combined with detailed models can provide constraints on the value of the power law index, the ratio of hydrogen to helium in the surface of the progenitor, the progenitor metallicity and the amount of radioactive nickel mixed into the outer envelope of the supernova. The spectral fits reproduce the observed spectra exceedingly well. The spectral results combined with the early photometry predict that the explosion date was 4.7 {+-} 0.7 days before the first spectrum was obtained. The ability to obtain the metallicity from early spectra make SN IIP attractive probes of chemical evolution in the universe and by showing that we have the ability to pin down the parameters of the progenitor and mixing during the supernova explosion, it is likely to make SN IIP useful cosmological distance indicators which are at the same time complementary to SNe Ia.
20 citations
Journal Article•
TL;DR: In this article, the authors quantify the major contributions of the Supernova/Acceleration Probe (SNAP) to the Point Spread Function (PSF) of the Wide Field Space Telescope (WFSST).
Abstract: A wide field space-based imaging telescope is necessary to fully exploit the technique of observing dark matter via weak gravitational lensing. This first paper in a three part series outlines the survey strategies and relevant instrumental parameters for such a mission. As a concrete example of hardware design, we consider the proposed Supernova/Acceleration Probe (SNAP). Using SNAP engineering models, we quantify the major contributions to this telescope's Point Spread Function (PSF). These PSF contributions are relevant to any similar wide field space telescope. We further show that the PSF of SNAP or a similar telescope will be smaller than current ground-based PSFs, and more isotropic and stable over time than the PSF of the Hubble Space Telescope. We outline survey strategies for two different regimes - a ''wide'' 300 square degree survey and a ''deep'' 15 square degree survey that will accomplish various weak lensing goals including statistical studies and dark matter mapping.
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University of California, Berkeley1, Lawrence Berkeley National Laboratory2, University of Michigan3, Stockholm University4, Centre national de la recherche scientifique5, Indiana University6, American Astronomical Society7, California Institute of Technology8, Space Telescope Science Institute9, Case Western Reserve University10, University of Cambridge11, Goddard Space Flight Center12
TL;DR: The SuperNova/Acceleration Probe (SNAP) mission as discussed by the authors has a two-meter class telescope delivering diffraction-limited images to an instrumented 0.7 square-degree field sensitive in the visible and near-infrared wavelength regime.
Abstract: The proposed SuperNova/Acceleration Probe (SNAP) mission will have a two-meter class telescope delivering diffraction-limited images to an instrumented 0.7 square-degree field sensitive in the visible and near-infrared wavelength regime. We describe the requirements for the instrument suite and the evolution of the focal plane design to the present concept in which all the instrumentation--visible and near-infrared imagers, spectrograph, and star guiders--share one common focal plane.
01 Jan 2003
TL;DR: Phillips et al. as discussed by the authors provided a progress report on a collaborative program at the Las Campanas and Cerro Tololo Observatories to observe the near-IR light curves of Type Ia supernovae and discussed how the morphologies of the JHK light curves change as a function of the decline rate.
Abstract: Author(s): Phillips, MM; Krisciunas, K; Suntzeff, NB; Roth, M; Germany, L; Candia, P; Gonzalez, S; Hamuy, M; Freedman, WL; Persson, SE; Nugent, PE; Aldering, G; Conley, A | Abstract: This paper provides a progress report on a collaborative program at the Las Campanas and Cerro Tololo Observatories to observe the near-IR light curves of Type Ia supernovae. We discuss how the morphologies of the JHK light curves change as a function of the decline rate. Evidence is presented which indicates that the absolute magnitudes in the H band have little or no dependence on the decline rate, suggesting that SNe Ia may be nearly perfect cosmological standard candles in the near-IR. A preliminary Hubble diagram in the H band is presented and compared with a similar diagram in V for the same objects. Finally, observations of two peculiar supernovae, 1999ac and 2001ay, are briefly discussed.
Centre national de la recherche scientifique1, University of Michigan2, Lawrence Berkeley National Laboratory3, Stockholm University4, University of Pennsylvania5, Indiana University6, University of California, Berkeley7, American Astronomical Society8, California Institute of Technology9, Space Telescope Science Institute10, Case Western Reserve University11, University of Cambridge12
TL;DR: In this article, a well-adapted spectrograph concept has been developed for the SNAP (SuperNova/Acceleration Probe) experiment to ensure proper identification of Type Ia supernovae and to standardize the magnitude of each candidate by determining explosion parameters.
Abstract: A well-adapted spectrograph concept has been developed for the SNAP (SuperNova/Acceleration Probe) experiment The goal is to ensure proper identification of Type Ia supernovae and to standardize the magnitude of each candidate by determining explosion parameters An instrument based on an integral field method with the powerful concept of imager slicing has been designed and is presented in this paper The spectrograph concept is optimized to have very high efficiency and low spectral resolution (R {approx} 100), constant through the wavelength range (035-17{micro}m), adapted to the scientific goals of the mission
TL;DR: In this article, the authors used multi-dimensional Monte Carlo radiative transfer calculations to explore the observable consequences of an ejecta-hole asymmetry in Type Ia supernovae, and found that the supernova looks normal from almost all viewing angles except when one looks almost directly down the hole.
Abstract: In the favored progenitor scenario, Type Ia supernovae arise from a white dwarf accreting material from a non-degenerate companion star. Soon after the white dwarf explodes, the ejected supernova material engulfs the companion star; two-dimensional hydrodynamical simulations by Marietta et. al. show that, in the interaction, the companion star carves out a conical hole of opening angle 30-40 degrees in the supernova ejecta. In this paper we use multi-dimensional Monte Carlo radiative transfer calculations to explore the observable consequences of an ejecta-hole asymmetry. We calculate the variation of the spectrum, luminosity, and polarization with viewing angle for the aspherical supernova near maximum light. We find that the supernova looks normal from almost all viewing angles except when one looks almost directly down the hole. In the latter case, one sees into the deeper, hotter layers of ejecta. The supernova is relatively brighter and has a peculiar spectrum characterized by more highly ionized species, weaker absorption features, and lower absorption velocities. The spectrum viewed down the hole is comparable to the class of SN 1991T-like supernovae. We consider how the ejecta-hole asymmetry may explain the current spectropolarimetric observations of SNe Ia, and suggest a few observational signatures of the geometry. Finally, we discuss the variety currently seen in observed SNe Ia and how an ejecta-hole asymmetry may fit in as one of several possible sources of diversity.
[...]
University of Michigan1, Lawrence Berkeley National Laboratory2, 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 the largest NIR system to date, having over 150 million pixels and a field-of-view of 0.34 square degrees.
Abstract: The SuperNova/Acceleration Probe (SNAP) will measure precisely the cosmological expansion history over both the acceleration and deceleration epochs and thereby constrain the nature of the dark energy that dominates our universe today. The SNAP focal plane contains equal areas of optical CCDs and NIR sensors and an integral field spectrograph. Having over 150 million pixels and a field-of-view of 0.34 square degrees, the SNAP NIR system will be the largest yet constructed. With sensitivity in the range 0.9-1.7 μm, it will detect Type Ia supernovae between z = 1 and 1.7 and will provide follow-up precision photometry for all supernovae. HgCdTe technology, with a cut-off tuned to 1.7 μm, will permit passive cooling at 140 K while maintaining noise below zodiacal levels. By dithering to remove the effects of intrapixel variations and by careful attention to other instrumental effects, we expect to control relative photometric accuracy below a few hundredths of a magnitude. Because SNAP continuously revisits the same fields we will be able to achieve outstanding statistical precision on the photometry of reference stars in these fields, allowing precise monitoring of our detectors. The capabilities of the NIR system for broadening the science reach of SNAP are discussed.
Lawrence Berkeley National Laboratory1, University of Michigan2, Centre national de la recherche scientifique3, Yale University4, University of Pennsylvania5, University of California, Berkeley6, Space Telescope Science Institute7, Indiana University8, American Astronomical Society9, California Institute of Technology10
TL;DR: The SuperNova/Acceleration Probe (SNAP) mission as mentioned in this paper has a two-meter class telescope delivering diffraction-limited images to an instrumented 0.7 square degree field in the visible and near-infrared wavelength regime.
Abstract: The proposed SuperNova/Acceleration Probe (SNAP) mission will have a two-meter class telescope delivering diffraction-limited images to an instrumented 0.7 square degree field in the visible and near-infrared wavelength regime. The requirements for the instrument suite and the present configuration of the focal plane concept are presented. A two year R&D phase, largely supported by the Department of Energy, is just beginning. We describe the development activities that are taking place to advance our preparedness for mission proposal in the areas of detectors and electronics.
01 Jan 2003
TL;DR: The Supernova / Acceleration Probe (SNAP) as discussed by the authors is a space-based experiment designed to measure the expansion history of the Universe, motivated by the discovery that the expansion is accelerating.
Abstract: The Supernova / Acceleration Probe (SNAP) is a proposed space-based experiment designed to measure the expansion history of the Universe, motivated by the discovery that the expansion is accelerating. It will study both the dark energy and the dark matter, through mapping the distanceredshift relation of Type Ia supernovae and through a wide-area weak gravitational lensing survey. A 2-m three mirror anastigmat wide-field telescope feeds a focal plane consisting of a 0.7 squaredegree imager tiled with equal areas of optical CCD’s and near infrared sensors, and a highefficiency low-resolution integral field spectrograph. The instrumentation suite provides simultaneous discovery and light-curve measurements for many supernovae with the capability to target individual objects for detailed spectral characterization. The SNAP mission can obtain highsignal-to-noise calibrated light-curves and spectra for over 2000 Type Ia supernovae at redshifts between z = 0.1 and 1.7. The resulting data set can not only determine the amount of dark energy with 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 or various classes of dynamical scalar fields can be differentiated, by measuring the dark energy’s equation of state density-to-pressure ratio to an accuracy of ± 0.05, and its time evolution to w' = dw/dz to ± 0.2. Although the survey strategy is tailored for supernova and weak gravitational lensing observations, the large survey area, depth, spatial resolution, time-sampling, and infrared extent of the resulting data will support a broad range of auxiliary science programs.