11,108 research outputs found
Cross-calibration of Time-of-flight and Colour Cameras
Time-of-flight cameras provide depth information, which is complementary to
the photometric appearance of the scene in ordinary images. It is desirable to
merge the depth and colour information, in order to obtain a coherent scene
representation. However, the individual cameras will have different viewpoints,
resolutions and fields of view, which means that they must be mutually
calibrated. This paper presents a geometric framework for this multi-view and
multi-modal calibration problem. It is shown that three-dimensional projective
transformations can be used to align depth and parallax-based representations
of the scene, with or without Euclidean reconstruction. A new evaluation
procedure is also developed; this allows the reprojection error to be
decomposed into calibration and sensor-dependent components. The complete
approach is demonstrated on a network of three time-of-flight and six colour
cameras. The applications of such a system, to a range of automatic
scene-interpretation problems, are discussed.Comment: 18 pages, 12 figures, 3 table
Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Data Processing, Sky Maps, and Basic Results
We present new full-sky temperature and polarization maps in five frequency
bands from 23 to 94 GHz, based on data from the first five years of the WMAP
sky survey. The five-year maps incorporate several improvements in data
processing made possible by the additional years of data and by a more complete
analysis of the instrument calibration and in-flight beam response. We present
several new tests for systematic errors in the polarization data and conclude
that Ka band data (33 GHz) is suitable for use in cosmological analysis, after
foreground cleaning. This significantly reduces the overall polarization
uncertainty. With the 5 year WMAP data, we detect no convincing deviations from
the minimal 6-parameter LCDM model: a flat universe dominated by a cosmological
constant, with adiabatic and nearly scale-invariant Gaussian fluctuations.
Using WMAP data combined with measurements of Type Ia supernovae and Baryon
Acoustic Oscillations, we find (68% CL uncertainties): Omega_bh^2 = 0.02267 \pm
0.00059, Omega_ch^2 = 0.1131 \pm 0.0034, Omega_Lambda = 0.726 \pm 0.015, n_s =
0.960 \pm 0.013, tau = 0.084 \pm 0.016, and Delta_R^2 = (2.445 \pm 0.096) x
10^-9. From these we derive: sigma_8 = 0.812 \pm 0.026, H_0 = 70.5 \pm 1.3
km/s/Mpc, z_{reion} = 10.9 \pm 1.4, and t_0 = 13.72 \pm 0.12 Gyr. The new limit
on the tensor-to-scalar ratio is r < 0.22 (95% CL). We obtain tight,
simultaneous limits on the (constant) dark energy equation of state and spatial
curvature: -0.14 < 1+w < 0.12 and -0.0179 < Omega_k < 0.0081 (both 95% CL). The
number of relativistic degrees of freedom (e.g. neutrinos) is found to be
N_{eff} = 4.4 \pm 1.5, consistent with the standard value of 3.04. Models with
N_{eff} = 0 are disfavored at >99.5% confidence.Comment: 46 pages, 13 figures, and 7 tables. Version accepted for publication,
ApJS, Feb-2009. Includes 5-year dipole results and additional references.
Also available at
http://lambda.gsfc.nasa.gov/product/map/dr3/map_bibliography.cf
Calibration and data quality of warm IRAC
We present an overview of the calibration and properties of data from the IRAC instrument aboard the Spitzer Space Telescope taken after the depletion of cryogen. The cryogen depleted on 15 May 2009, and shortly afterward a two-month- long calibration and characterization campaign was conducted. The array temperature and bias setpoints were revised on 19 September 2009 to take advantage of lower than expected power dissipation by the instrument and to improve sensitivity. The final operating temperature of the arrays is 28.7 K, the applied bias across each detector is 500 mV and the equilibrium temperature of the instrument chamber is 27.55 K. The final sensitivities are essentially the same as the cryogenic mission with the 3.6 μm array being slightly less sensitive (10%) and the 4.5 μm array within 5% of the cryogenic sensitivity. The current absolute photometric uncertainties are 4% at 3.6 and 4.5 μm, and better than milli-mag photometry is achievable for long-stare photometric observations. With continued analysis, we expect the absolute calibration to improve to the cryogenic value of 3%. Warm IRAC operations fully support all science that was conducted in the cryogenic mission and all currently planned warm science projects (including Exploration Science programs). We expect that IRAC will continue to make ground-breaking discoveries in star formation, the nature of the early universe, and in our understanding of the properties of exoplanets
Astrometry with the Wide-Field InfraRed Space Telescope
The Wide-Field InfraRed Space Telescope (WFIRST) will be capable of
delivering precise astrometry for faint sources over the enormous field of view
of its main camera, the Wide-Field Imager (WFI). This unprecedented combination
will be transformative for the many scientific questions that require precise
positions, distances, and velocities of stars. We describe the expectations for
the astrometric precision of the WFIRST WFI in different scenarios, illustrate
how a broad range of science cases will see significant advances with such
data, and identify aspects of WFIRST's design where small adjustments could
greatly improve its power as an astrometric instrument.Comment: version accepted to JATI
Spectral Typing of Late Type Stellar Companions to Young Stars from Low Dispersion Near-Infrared Integral Field Unit Data
We used the Project 1640 near-infrared coronagraph and integral field
spectrograph to observe 19 young solar type stars. Five of these stars are
known binary stars and we detected the late-type secondaries and were able to
measure their JH spectra with a resolution of R\sim30. The reduced, extracted,
and calibrated spectra were compared to template spectra from the IRTF spectral
library. With this comparison we test the accuracy and consistency of spectral
type determination with the low-resolution near-infrared spectra from P1640.
Additionally, we determine effective temperature and surface gravity of the
companions by fitting synthetic spectra calculated with the PHOENIX model
atmosphere code. We also present several new epochs of astrometry of each of
the systems. Together these data increase our knowledge and understanding of
the stellar make up of these systems. In addition to the astronomical results,
the analysis presented helps validate the Project 1640 data reduction and
spectral extraction processes and the utility of low-resolution, near-infrared
spectra for characterizing late-type companions in multiple systems.Comment: Accepted to Astronomical Journal, 25 pages, 8 figure
The Bolocam Galactic Plane Survey: Survey Description and Data Reduction
We present the Bolocam Galactic Plane Survey (BGPS), a 1.1 mm continuum
survey at 33" effective resolution of 170 square degrees of the Galactic Plane
visible from the northern hemisphere. The survey is contiguous over the range
-10.5 < l < 90.5, |b| < 0.5 and encompasses 133 square degrees, including some
extended regions |b| < 1.5. In addition to the contiguous region, four targeted
regions in the outer Galaxy were observed: IC1396, a region towards the Perseus
Arm, W3/4/5, and Gem OB1. The BGPS has detected approximately 8400 clumps over
the entire area to a limiting non-uniform 1-sigma noise level in the range 11
to 53 mJy/beam in the inner Galaxy. The BGPS source catalog is presented in a
companion paper (Rosolowsky et al. 2010). This paper details the survey
observations and data reduction methods for the images. We discuss in detail
the determination of astrometric and flux density calibration uncertainties and
compare our results to the literature. Data processing algorithms that separate
astronomical signals from time-variable atmospheric fluctuations in the data
time-stream are presented. These algorithms reproduce the structure of the
astronomical sky over a limited range of angular scales and produce artifacts
in the vicinity of bright sources. Based on simulations, we find that extended
emission on scales larger than about 5.9' is nearly completely attenuated (>
90%) and the linear scale at which the attenuation reaches 50% is 3.8'.
Comparison with other millimeter-wave data sets implies a possible systematic
offset in flux calibration, for which no cause has been discovered. This
presentation serves as a companion and guide to the public data release through
NASA's Infrared Processing and Analysis Center (IPAC) Infrared Science Archive
(IRSA). New data releases will be provided through IPAC IRSA with any future
improvements in the reduction.Comment: Accepted for publication in Astrophysical Journal Supplemen
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