591 research outputs found
Spitzer Observations of Interstellar Object 1I/`Oumuamua
1I/`Oumuamua is the first confirmed interstellar body in our Solar System.
Here we report on observations of `Oumuamua made with the Spitzer Space
Telescope on 2017 November 21--22 (UT). We integrated for 30.2~hours at 4.5
micron (IRAC channel 2). We did not detect the object and place an upper limit
on the flux of 0.3 uJy (3sigma). This implies an effective spherical diameter
less than [98, 140, 440] meters and albedo greater than [0.2, 0.1, 0.01] under
the assumption of low, middle, or high thermal beaming parameter eta,
respectively. With an aspect ratio for `Oumuamua of 6:1, these results
correspond to dimensions of [240:40, 341:57, 1080:180] meters, respectively. We
place upper limits on the amount of dust, CO, and CO2 coming from this object
that are lower than previous results; we are unable to constrain the production
of other gas species. Both our size and outgassing limits are important because
`Oumuamua's trajectory shows non-gravitational accelerations that are sensitive
to size and mass and presumably caused by gas emission. We suggest that
`Oumuamua may have experienced low-level post-perihelion volatile emission that
produced a fresh, bright, icy mantle. This model is consistent with the
expected eta value and implied high albedo value for this solution, but, given
our strict limits on CO and CO2, requires another gas species --- probably H2O
--- to explain the observed non-gravitational acceleration. Our results extend
the mystery of `Oumuamua's origin and evolution
The detection efficiency of on-axis short gamma ray burst optical afterglows triggered by aLIGO/Virgo
Assuming neutron star (NS) or neutron star/stellar-mass black hole (BH)
mergers as progenitors of the short gamma ray bursts, we derive and demonstrate
a simple analysis tool for modelling the efficiency of recovering on-axis
optical afterglows triggered by a candidate gravitational wave event detected
by the Advanced LIGO and Virgo network. The coincident detection efficiency has
been evaluated for different classes of operating telescopes using observations
of gamma ray bursts. We show how the efficiency depends on the luminosity
distribution of the optical afterglows, the telescope features, and the sky
localisation of gravitational wave triggers. We estimate a plausible optical
afterglow and gravitational wave coincidence rate of 1 yr (0.1
yr) for NS-NS (NS-BH), and how this rate is scaled down in detection
efficiency by the time it takes to image the gravitational wave sky
localization and the limiting magnitude of the telescopes. For NS-NS (NS-BH) we
find maximum detection efficiencies of when the total imaging time is
less than 200 min (80 min) and the limiting magnitude fainter than 20 (21). We
show that relatively small telescopes can achieve similar detection
efficiencies to meter class facilities with similar fields of view,
only if the less sensitive instruments can respond to the trigger and image the
field within 10-15 min. The inclusion of LIGO India into the gravitational wave
observatory network will significantly reduce imaging time for telescopes with
limiting magnitudes but with modest fields of view. An optimal
coincidence search requires a global network of sensitive and fast response
wide field instruments that could effectively image relatively large
gravitational-wave sky localisations and produce transient candidates for
further photometric and spectroscopic follow-up.Comment: 6 pages, 2 figures, version 2, reference added typo correction,
Accepted by MNRA
DISCUS - The Deep Interior Scanning CubeSat mission to a rubble pile near-Earth asteroid
We have performed an initial stage conceptual design study for the Deep
Interior Scanning CubeSat (DISCUS), a tandem 6U CubeSat carrying a bistatic
radar as main payload. DISCUS will be operated either as an independent mission
or accompanying a larger one. It is designed to determine the internal
macroporosity of a 260-600 m diameter Near Earth Asteroid (NEA) from a few
kilometers distance. The main goal will be to achieve a global penetration with
a low-frequency signal as well as to analyze the scattering strength for
various different penetration depths and measurement positions. Moreover, the
measurements will be inverted through a computed radar tomography (CRT)
approach. The scientific data provided by DISCUS would bring more knowledge of
the internal configuration of rubble pile asteroids and their collisional
evolution in the Solar System. It would also advance the design of future
asteroid deflection concepts. We aim at a single-unit (1U) radar design
equipped with a half-wavelength dipole antenna. The radar will utilize a
stepped-frequency modulation technique the baseline of which was developed for
ESA's technology projects GINGER and PIRA. The radar measurements will be used
for CRT and shape reconstruction. The CubeSat will also be equipped with an
optical camera system and laser altimeter to sup- port navigation and shape
reconstruction. We provide the details of the measurement methods to be applied
along with the requirements derived of the known characteristics of rubble pile
asteroids.Comment: Submitted to Advances in Space Researc
LSST: from Science Drivers to Reference Design and Anticipated Data Products
(Abridged) We describe here the most ambitious survey currently planned in
the optical, the Large Synoptic Survey Telescope (LSST). A vast array of
science will be enabled by a single wide-deep-fast sky survey, and LSST will
have unique survey capability in the faint time domain. 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 wide-field ground-based system sited at
Cerro Pach\'{o}n in northern Chile. The telescope will have an 8.4 m (6.5 m
effective) primary mirror, a 9.6 deg field of view, and a 3.2 Gigapixel
camera. The standard observing sequence will consist of pairs of 15-second
exposures in a given field, with two such visits in each pointing in a given
night. With these repeats, the LSST system is capable of imaging about 10,000
square degrees of sky in a single filter in three nights. The typical 5
point-source depth in a single visit in will be (AB). The
project is in the construction phase and will begin regular survey operations
by 2022. The survey area will be contained within 30,000 deg with
, and will be imaged multiple times in six bands, ,
covering the wavelength range 320--1050 nm. About 90\% of the observing time
will be devoted to a deep-wide-fast survey mode which will uniformly observe a
18,000 deg region about 800 times (summed over all six bands) during the
anticipated 10 years of operations, and yield a coadded map to . The
remaining 10\% of the observing time will be allocated to projects such as a
Very Deep and Fast time domain survey. The goal is to make LSST data products,
including a relational database of about 32 trillion observations of 40 billion
objects, available to the public and scientists around the world.Comment: 57 pages, 32 color figures, version with high-resolution figures
available from https://www.lsst.org/overvie
LSST Science Book, Version 2.0
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.Comment: 596 pages. Also available at full resolution at
http://www.lsst.org/lsst/sciboo
First searches for optical counterparts to gravitational-wave candidate events
During the Laser Interferometer Gravitational-wave Observatory and Virgo joint science runs in 2009-2010, gravitational wave (GW) data from three interferometer detectors were analyzed within minutes to select GW candidate events and infer their apparent sky positions. Target coordinates were transmitted to several telescopes for follow-up observations aimed at the detection of an associated optical transient. Images were obtained for eight such GW candidates. We present the methods used to analyze the image data as well as the transient search results. No optical transient was identified with a convincing association with any of these candidates, and none of the GW triggers showed strong evidence for being astrophysical in nature. We compare the sensitivities of these observations to several model light curves from possible sources of interest, and discuss prospects for future joint GW-optical observations of this type. © 2014. The American Astronomical Society. All rights reserved
First searches for optical counterparts to gravitational-wave candidate events
During the Laser Interferometer Gravitational-wave Observatory and Virgo joint science runs in 2009-2010, gravitational wave (GW) data from three interferometer detectors were analyzed within minutes to select GW candidate events and infer their apparent sky positions. Target coordinates were transmitted to several telescopes for follow-up observations aimed at the detection of an associated optical transient. Images were obtained for eight such GW candidates. We present the methods used to analyze the image data as well as the transient search results. No optical transient was identified with a convincing association with any of these candidates, and none of the GW triggers showed strong evidence for being astrophysical in nature. We compare the sensitivities of these observations to several model light curves from possible sources of interest, and discuss prospects for future joint GW-optical observations of this type. Ă© 2014. The American Astronomical Society. All rights reserved
First Searches for Optical Counterparts to Gravitational-Wave Candidate Events
During the Laser Interferometer Gravitational-wave Observatory and Virgo joint science runs in 2009-2010, gravitational wave (GW) data from three interferometer detectors were analyzed within minutes to select GW candidate events and infer their apparent sky positions. Target coordinates were transmitted to several telescopes for follow-up observations aimed at the detection of an associated optical transient. Images were obtained for eight such GW candidates. We present the methods used to analyze the image data as well as the transient search results. No optical transient was identified with a convincing association with any of these candidates, and none of the GW triggers showed strong evidence for being astrophysical in nature. We compare the sensitivities of these observations to several model light curves from possible sources of interest, and discuss prospects for future joint GW-optical observations of this type
Conference on Spacecraft Reconnaissance of Asteroid and Comet Interiors : January 8-10, 2015, Tempe, Arizona
The goal of AstroRecon is to identify and evaluate the best technologies for spacecraft robotic reconnaissance of comets, asteroids, and small moons--paving the way for advanced science missions, exploration, sample return, in situ resource utilization, hazard mitigation, and human visitation.Shell GameChanger, ASU NewSpace, The Johns Hopkins University Applied Physics Laboratoryinstitutional support Arizona State University, Lunar and Planetary Institute, National Aeronautics and Space Administration, Universities Space Research Association Arizona State University's Students for the Exploration and Development of Space ; sponsors Shell GameChanger, ASU NewSpace, The Johns Hopkins University Applied Physics Laboratory ; conveners Erik Asphaug Arizona State University, Tempe, Jekan Thangavelautham Arizona State University, Tempe ; program committee Erik Asphaug (Co-chair Science) Arizona State University, Tempe [and 6 others].PARTIAL CONTENTS: Human Exploration / P. A. Abell and A. S. Rivkin--Comet Radar Explorer / E. Asphaug--Development of Communication Technologies and Architectural Concepts for Interplanetary Small Satellite Communications / A. B. Babuscia and K. C. Cheung--Numerical Simulations of Spacecraft-Regolith Interactions on Asteroids / R.-L. Ballouz, D. C. Richardson, P. Michel, and S. R. Schwartz--Kuiper: A Discover, Class Observatory for Outer Solar System Giant Planets, Satellites, and Small Bodies / J. F. Bell, N. M. Schneider, M. E. Brown, J. T. Clarke, B. T. Greenhagen, R. M.C. Lopes, A. R. Hendrix, and M. H. Wong--Landing on Small Bodies: From the Rosetta Lander to MASCOT and Beyond / J. Biele, S. Ulamec, P.-W. Bousquet, P. Gaudon, K. Geurts, T.-M. Ho, C. Krause, R. Willnecker, and M. Deleuze--High-Resolution Bistatic Radar Imaging in Support of Asteroid and Comet Spacecraft Missions / M. W. Busch, L. A. M. Benner, M. A. Slade, L. Teitelbaum, M. Brozovic, M. C. Nolan, P. A. Taylor, F. Ghigo, and J. Ford--Asteroid Comet and Surface Gravimetric Surveying can Reveal Interior Structural Details / K. A. Carroll
First Searches for Optical Counterparts to Gravitational-Wave Candidate Events
During the Laser Interferometer Gravitational-wave Observatory and Virgo joint science runs in 2009-2010, gravitational wave (GW) data from three interferometer detectors were analyzed within minutes to select GW candidate events and infer their apparent sky positions. Target coordinates were transmitted to several telescopes for follow-up observations aimed at the detection of an associated optical transient. Images were obtained for eight such GW candidates. We present the methods used to analyze the image data as well as the transient search results. No optical transient was identified with a convincing association with any of these candidates, and none of the GW triggers showed strong evidence for being astrophysical in nature. We compare the sensitivities of these observations to several model light curves from possible sources of interest, and discuss prospects for future joint GW-optical observations of this type
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