399 research outputs found
Interpretable Categorization of Heterogeneous Time Series Data
Understanding heterogeneous multivariate time series data is important in
many applications ranging from smart homes to aviation. Learning models of
heterogeneous multivariate time series that are also human-interpretable is
challenging and not adequately addressed by the existing literature. We propose
grammar-based decision trees (GBDTs) and an algorithm for learning them. GBDTs
extend decision trees with a grammar framework. Logical expressions derived
from a context-free grammar are used for branching in place of simple
thresholds on attributes. The added expressivity enables support for a wide
range of data types while retaining the interpretability of decision trees. In
particular, when a grammar based on temporal logic is used, we show that GBDTs
can be used for the interpretable classi cation of high-dimensional and
heterogeneous time series data. Furthermore, we show how GBDTs can also be used
for categorization, which is a combination of clustering and generating
interpretable explanations for each cluster. We apply GBDTs to analyze the
classic Australian Sign Language dataset as well as data on near mid-air
collisions (NMACs). The NMAC data comes from aircraft simulations used in the
development of the next-generation Airborne Collision Avoidance System (ACAS
X).Comment: 9 pages, 5 figures, 2 tables, SIAM International Conference on Data
Mining (SDM) 201
Microlens Parallax Measurements with a Warm Spitzer
Because Spitzer is an Earth-trailing orbit, losing about 0.1 AU/yr, it is
excellently located to perform microlens parallax observations toward the
Magellanic Clouds (LMC/SMC) and the Galactic bulge. These yield the so-called
``projected velocity'' of the lens, which can distinguish statistically among
different populations. A few such measurements toward the LMC/SMC would reveal
the nature of the lenses being detected in this direction (dark halo objects,
or ordinary LMC/SMC stars). Cool Spitzer has already made one such measurement
of a (rare) bright red-clump source, but warm (presumably less oversubscribed)
Spitzer could devote the extra time required to obtain microlens parallaxes for
the more common, but fainter, turnoff sources. Warm Spitzer could observe bulge
microlenses for 38 days per year, which would permit up to 24 microlens
parallaxes per year. This would yield interesting information on the disk mass
function, particularly old brown dwarfs, which at present are inaccessible by
other techniques. Target-of-Opportunity (TOO) observations should be divided
into RTOO/DTOO, i.e., ``regular'' and ``disruptive'' TOOs, as pioneered by the
Space Interferometry Mission (SIM). LMC/SMC parallax measurements would be
DTOO, but bulge measurements would be RTOO, i.e., they could be scheduled in
advance, without knowing exactly which star was to be observed.Comment: 6 pages + 1 Figure, To be presented at The Warm Spitzer Mission
Workshop, 4-5 June 2007, Pasaden
Spitzer Warm Mission Workshop Introduction
The Spitzer Warm Mission Workshop was held June 4–5, 2007, to explore the science drivers for the warm Spitzer mission and help the Spitzer Science Center develop a new science operations philosophy. We must continue to maximize the science return with the reduced resources available, both using (a) the shortest two IRAC channels, and (b) archival research with the rich Spitzer archive. This paper summarizes the overview slides presented to the workshop participant
The Warm Spitzer Mission: Prospects for Studies of the Distant Universe
IRAC excels at detecting distant objects. Due to a combination of the shapes
of the spectral energy distributions of galaxies and the low background
achieved from space, IRAC reaches greater depth in comparable exposure time at
3.6 and 4.5 micron than any ground- or space-based facility currently can at
2.2 micron. Furthermore, the longer wavelengths probed by IRAC enable studies
of the rest-frame optical and near-infrared light of galaxies and AGN to much
higher redshift than is possible from the ground. This white paper explores the
merits of different survey strategies for studying the distant universe during
the warm mission. A three-tiered approach serves a wide range of science goals
and uses the spacecraft effectively: 1) an ultra-deep survey of ~0.04 square
degrees to a depth of ~250 hrs (in conjunction with an HST/WFC3 program), to
study the Universe at 7<z<14; 2) a survey of ~2 square degrees to the GOODS
depth of 20 hrs, to identify luminous galaxies at z>6 and characterize the
relation between the build-up of dark matter halos and their constituent
galaxies at 2<z<6, and 3) a 500 square degree survey to the SWIRE depth of 120
s, to systematically study large scale structure at 1<z<2 and characterize high
redshift AGN. One or more of these programs could conceivably be implemented by
the SSC, following the example of the Hubble Deep Field campaigns. As
priorities in this field continuously shift it is also crucial that a fraction
of the exposure time remains unassigned, thus enabling science that will
reflect the frontiers of 2010 and beyond rather than those of 2007.Comment: White paper to appear in "The Science Opportunities for the Warm
Spitzer Mission". 15 page
Observations of Extrasolar Planets During the non-Cryogenic Spitzer Space Telescope Mission
Precision infrared photometry from Spitzer has enabled the first direct
studies of light from extrasolar planets, via observations at secondary eclipse
in transiting systems. Current Spitzer results include the first longitudinal
temperature map of an extrasolar planet, and the first spectra of their
atmospheres. Spitzer has also measured a temperature and precise radius for the
first transiting Neptune-sized exoplanet, and is beginning to make precise
transit timing measurements to infer the existence of unseen low mass planets.
The lack of stellar limb darkening in the infrared facilitates precise radius
and transit timing measurements of transiting planets. Warm Spitzer will be
capable of a precise radius measurement for Earth-sized planets transiting
nearby M-dwarfs, thereby constraining their bulk composition. It will continue
to measure thermal emission at secondary eclipse for transiting hot Jupiters,
and be able to distinguish between planets having broad band emission versus
absorption spectra. It will also be able to measure the orbital phase variation
of thermal emission for close-in planets, even non-transiting planets, and
these measurements will be of special interest for planets in eccentric orbits.
Warm Spitzer will be a significant complement to Kepler, particularly as
regards transit timing in the Kepler field. In addition to studying close-in
planets, Warm Spitzer will have significant application in sensitive imaging
searches for young planets at relatively large angular separations from their
parent stars.Comment: 12 pages, 7 figures, to appear in "Science Opportunities for the Warm
Spitzer Mission
The Porcupine Survey: A Distributed Survey and WISE Followup
Spitzer post-cryogen observations to perform a moderate depth survey distributed around the sky are proposed. Field centers are chosen to be WISE brown dwarf candidates, which will typically be 160 µJy at 4.7 µm and randomly distributed around the sky. The Spitzer observations will give much higher sensitivity, higher angular resolution, and a time baseline to measure both proper motions and possibly parallaxes. The distance and velocity data obtained on the WISE brown dwarf candidates will greatly improve our knowledge of the mass and age distribution of brown dwarfs. The outer parts of the Spitzer fields surrounding the WISE positions will provide a deep survey in many narrow fields of view distributed around the sky, and the volume of this survey will contain many more distant brown dwarfs, and many extragalactic objects
Planetary Science Goals for the Spitzer Warm Era
The overarching goal of planetary astronomy is to deduce how the present collection of objects found in our Solar System were formed from the original material present in the proto-solar nebula. As over two hundred exo-planetary systems are now known, and multitudes more are expected, the Solar System represents the closest and best system which we can study, and the only one in which we can clearly resolve individual bodies other than planets. In this White Paper we demonstrate how to use Spitzer Space Telescope InfraRed Array Camera Channels 1 and 2 (3.6 and 4.5 µm) imaging photometry with large dedicated surveys to advance our knowledge of Solar System formation and evolution. There are a number of vital, key projects to be pursued using dedicated large programs that have not been pursued during the five years of Spitzer cold operations. We present a number of the largest and most important projects here; more will certainly be proposed once the warm era has begun, including important observations of newly discovered objects
SPRITE: the Spitzer proposal review website
The Spitzer Science Center (SSC), located on the campus of the California Institute of Technology, supports the science operations of NASA's infrared Spitzer Space Telescope. The SSC issues an annual Call for Proposals inviting investigators worldwide to submit Spitzer Space Telescope proposals. The Spitzer Proposal Review Website (SPRITE) is a MySQL/PHP web database application designed to support the SSC proposal review process. Review panel members use the software to view, grade, and write comments about the proposals, and SSC support team members monitor the grading and ranking process and ultimately generate a ranked list of all the proposals. The software is also used to generate, edit, and email award letters to the proposers. This work was performed at the California Institute of Technology under contract to the National Aeronautics and Space Administration
The Mid-Infrared Spectra of Normal Galaxies
The mid-infrared spectra (2.5 to 5 and 5.7 to 11.6 mu) obtained by ISO-PHOT
reveal the interstellar medium emission from galaxies powered by star formation
to be strongly dominated by the aromatic features at 6.2, 7.7, 8.6 and 11.3 mu.
Additional emission appears in-between the features, and an underlying
continuum is clearly evident at 3-5 mu. This continuum would contribute about a
third of the luminosity in the 3 to 13 mu range. The features together carry 5
to 30% of the 40-to-120 mu `FIR' luminosity. The relative fluxes in individual
features depend very weakly on galaxy parameters such as the far-infrared
colors, direct evidence that the emitting particles are not in thermal
equilibrium. The dip at 10 mu is unlikely to result from silicate absorption,
since its shape is invariant among galaxies. The continuum component has a f_nu
\~ nu^{0.65} shape between 3 and 5 mu and carries 1 to 4% of the FIR
luminosity; its extrapolation to longer wavelengths falls well below the
spectrum in the 6 to 12 mu range. This continuum component is almost certainly
of non-stellar origin, and is probably due to fluctuating grains without
aromatic features. The spectra reported here typify the integrated emission
from the interstellar medium of the majority of star-forming galaxies, and
could thus be used to obtain redshifts of highly extincted galaxies up to z=3
with SIRTF.Comment: 10 pages, 2 figures, uses AAS LaTeX; to appear in the Astrophysical
Journal Letter
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