18,439 research outputs found
NEOWISE Observations of Near-Earth Objects: Preliminary Results
With the NEOWISE portion of the \emph{Wide-field Infrared Survey Explorer}
(WISE) project, we have carried out a highly uniform survey of the near-Earth
object (NEO) population at thermal infrared wavelengths ranging from 3 to 22
m, allowing us to refine estimates of their numbers, sizes, and albedos.
The NEOWISE survey detected NEOs the same way whether they were previously
known or not, subject to the availability of ground-based follow-up
observations, resulting in the discovery of more than 130 new NEOs. The
survey's uniformity in sensitivity, observing cadence, and image quality have
permitted extrapolation of the 428 near-Earth asteroids (NEAs) detected by
NEOWISE during the fully cryogenic portion of the WISE mission to the larger
population. We find that there are 98119 NEAs larger than 1 km and
20,5003000 NEAs larger than 100 m. We show that the Spaceguard goal of
detecting 90% of all 1 km NEAs has been met, and that the cumulative size
distribution is best represented by a broken power law with a slope of
1.320.14 below 1.5 km. This power law slope produces 1,900
NEAs with 140 m. Although previous studies predict another break in the
cumulative size distribution below 50-100 m, resulting in an increase in
the number of NEOs in this size range and smaller, we did not detect enough
objects to comment on this increase. The overall number for the NEA population
between 100-1000 m are lower than previous estimates. The numbers of near-Earth
comets will be the subject of future work.Comment: Accepted to Ap
Shape models and physical properties of asteroids
Despite the large amount of high quality data generated in recent space
encounters with asteroids, the majority of our knowledge about these objects
comes from ground based observations. Asteroids travelling in orbits that are
potentially hazardous for the Earth form an especially interesting group to be
studied. In order to predict their orbital evolution, it is necessary to
investigate their physical properties. This paper briefly describes the data
requirements and different techniques used to solve the lightcurve inversion
problem. Although photometry is the most abundant type of observational data,
models of asteroids can be obtained using various data types and techniques. We
describe the potential of radar imaging and stellar occultation timings to be
combined with disk-integrated photometry in order to reveal information about
physical properties of asteroids.Comment: From Assessment and Mitigation of Asteroid Impact Hazards boo
FLAT2D: Fast localization from approximate transformation into 2D
Many autonomous vehicles require precise localization into a prior map in order to support planning and to leverage semantic information within those maps (e.g. that the right lane is a turn-only lane.) A popular approach in automotive systems is to use infrared intensity maps of the ground surface to localize, making them susceptible to failures when the surface is obscured by snow or when the road is repainted. An emerging alternative is to localize based on the 3D structure around the vehicle; these methods are robust to these types of changes, but the maps are costly both in terms of storage and the computational cost of matching. In this paper, we propose a fast method for localizing based on 3D structure around the vehicle using a 2D representation. This representation retains many of the advantages of "full" matching in 3D, but comes with dramatically lower space and computational requirements. We also introduce a variation of Graph-SLAM tailored to support localization, allowing us to make use of graph-based error-recovery techniques in our localization estimate. Finally, we present real-world localization results for both an indoor mobile robotic platform and an autonomous golf cart, demonstrating that autonomous vehicles do not need full 3D matching to accurately localize in the environment
Efficient intra- and inter-night linking of asteroid detections using kd-trees
The Panoramic Survey Telescope And Rapid Response System (Pan-STARRS) under
development at the University of Hawaii's Institute for Astronomy is creating
the first fully automated end-to-end Moving Object Processing System (MOPS) in
the world. It will be capable of identifying detections of moving objects in
our solar system and linking those detections within and between nights,
attributing those detections to known objects, calculating initial and
differentially-corrected orbits for linked detections, precovering detections
when they exist, and orbit identification. Here we describe new kd-tree and
variable-tree algorithms that allow fast, efficient, scalable linking of intra
and inter-night detections. Using a pseudo-realistic simulation of the
Pan-STARRS survey strategy incorporating weather, astrometric accuracy and
false detections we have achieved nearly 100% efficiency and accuracy for
intra-night linking and nearly 100% efficiency for inter-night linking within a
lunation. At realistic sky-plane densities for both real and false detections
the intra-night linking of detections into `tracks' currently has an accuracy
of 0.3%. Successful tests of the MOPS on real source detections from the
Spacewatch asteroid survey indicate that the MOPS is capable of identifying
asteroids in real data.Comment: Accepted to Icaru
MarsBots: Robotic Learning Module
This learning module offers hands-on, minds-on activities investigating the Martian environment and robotic technologies of space exploration. The learning module contains 16 national standards-based lessons designed to progress logically from learning about Mars and why scientists and engineers want to explore Mars with robots (lessons 1 through 8) to the fundamental principles of robotics and how these principles are applied to design, construct, and test robotic explorer (lessons 9 through 16). The module is integrated to support fundamental concepts and skills in language arts, mathematics, and science. A background section along with teacher notes provide information needed to present each lesson. Educational levels: Intermediate elementary
An experimental investigation of the angular scattering and backscattering behaviors of the simulated clouds of the outer planets
A cryogenic, 50 liter volume Planetary Cloud Simulation Chamber has been constructed to permit the laboratory study of the cloud compositions which are likely to be found in the atmospheres of the outer planets. On the basis of available data, clouds composed of water ice, carbon dioxide, and liquid and solid ammonia and methane, both pure and in various mixtures, have been generated. Cloud microphysical observations have been permitted through the use of a cloud particle slide injector and photomicrography. Viewports in the lower chamber have enabled the collection of cloud backscattering data using 633 and 838 nm laser light, including linear depolarization ratios and complete Stokes parameterization. The considerable technological difficulties associated with the collection of angular scattering patterns within the chamber, however, could not be completely overcome
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