669 research outputs found
Multi Sector Planning Tools for Trajectory-Based Operations
This paper discusses a suite of multi sector planning tools for trajectory-based operations that were developed and evaluated in the Airspace Operations Laboratory (AOL) at the NASA Ames Research Center. The toolset included tools for traffic load and complexity assessment as well as trajectory planning and coordination. The situation assessment tools included an integrated suite of interactive traffic displays, load tables, load graphs, and dynamic aircraft filters. The planning toolset allowed for single and multi aircraft trajectory planning and data communication-based coordination of trajectories between operators. Also newly introduced was a real-time computation of sector complexity into the toolset that operators could use in lieu of aircraft count to better estimate and manage sector workload, especially in situations with convective weather. The tools were used during a joint NASA/FAA multi sector planner simulation in the AOL in 2009 that had multiple objectives with the assessment of the effectiveness of the tools being one of them. Current air traffic control operators who were experienced as area supervisors and traffic management coordinators used the tools throughout the simulation and provided their usefulness and usability ratings in post simulation questionnaires. This paper presents these subjective assessments as well as the actual usage data that was collected during the simulation. The toolset was rated very useful and usable overall. Many elements received high scores by the operators and were used frequently and successfully. Other functions were not used at all, but various requests for new functions and capabilities were received that could be added to the toolset
The Reddest DR3 SDSS/XMM Quasars
We have cross-correlated the SDSS DR3 Schneider et al. (2005) quasar catalog
with the XMM-Newton archive. Color and redshift selections (g - r > 0.5 and 0.9
z < 2.1) result in a sample of 17 red, moderate redshift quasars. The redshift
selection minimizes possible contamination due to host galaxy emission and
Lyalpha forest absorption. Both optical and X-ray information are required to
distinguish between the two likely remaining causes of the red colors: 1)
dust-reddening and 2) an intrinsically red continuum. We find that 7 of 17
quasars can be classified as probable `intrinsically red' objects. These 7
quasars have unusually broad MgII emission lines (=10,500 km s^{-1}),
moderately flat, but unabsorbed X-ray spectra =1.66+/-0.08), and low
accretion rates (mdot/mdot_{Edd}} ~ 0.01). We suggest low accretion rates as a
possible physical explanation for quasars with intrinsically red optical
continua. We find that 8 of 17 quasars can be classified as dust-reddened.
Three of these have upper-limits on the absorption column from X-ray spectral
fits of N_H = 3-13 x 10^{22} cm^2, while the other five quasars must be
absorbed by at least N_H = 10^{23} cm^2 in order to be consistent with a
comparably selected alpha_{ox}-l_{uv} distribution. Two objects in the sample
are unclassified.Comment: 20 pages, 12 figures, Accepted for publication in Ap
Spitzer Observations of the z=2.73 Lensed Lyman Break Galaxy, MS1512-cB58
We present Spitzer infrared (IR) photometry and spectroscopy of the lensed
Lyman break galaxy (LBG), MS1512-cB58 at z=2.73. The large (factor ~30)
magnification allows for the most detailed infrared study of an L*_UV(z=3) LBG
to date. Broadband photometry with IRAC (3-10 micron), IRS (16 micron), and
MIPS (24, 70 & 160 micron) was obtained as well as IRS spectroscopy spanning
5.5-35 microns. A fit of stellar population models to the optical/near-IR/IRAC
photometry gives a young age (~9 Myr), forming stars at ~98 M_sun/yr, with a
total stellar mass of ~10^9 M_sun formed thus far. The existence of an old
stellar population with twice the stellar mass can not be ruled out. IR
spectral energy distribution fits to the 24 and 70 micron photometry, as well
as previously obtained submm/mm, data give an intrinsic IR luminosity L_IR =
1-2 x10^11 L_sun and a star formation rate, SFR ~20-40 M_sun/yr. The UV derived
star formation rate (SFR) is ~3-5 times higher than the SFR determined using
L_IR or L_Halpha because the red UV spectral slope is significantly over
predicting the level of dust extinction. This suggests that the assumed
Calzetti starburst obscuration law may not be valid for young LBGs. We detect
strong line emission from Polycyclic Aromatic Hydrocarbons (PAHs) at 6.2, 7.7,
and 8.6 microns. The line ratios are consistent with ratios observed in both
local and high redshift starbursts. Both the PAH and rest-frame 8 micron
luminosities predict the total L_IR based on previously measured relations in
starbursts. Finally, we do not detect the 3.3 micron PAH feature. This is
marginally inconsistent with some PAH emission models, but still consistent
with PAH ratios measured in many local star-forming galaxies.Comment: Accepted for publication in ApJ. aastex format, 18 pages, 7 figure
New Improved Photometric Redshifts of Galaxies in the HDF
We report new improved photometric redshifts of 1048 galaxies in the Hubble
Deep Field (HDF). A standard chi^2 minimizing method is applied to seven-color
UBVIJHK photometry by Fernandez-Soto, Lanzetta, & Yahil (1999). We use 187
template SEDs representing a wide variety of morphology and age of observed
galaxies based on a population synthesis model by Kodama & Arimoto (1997). We
introduce two new recipes. First, the amount of the internal absorption is
changed as a free parameter in the range of E(B-V)=0.0 to 0.5 with an interval
of 0.1. Second, the absorption due to intergalactic HI clouds is also changed
by a factor of 0.5, 1.0, and 1.5 around the opacity given by Madau (1995). The
total number of template SEDs is thus 187x6x3=3,366, except for the redshift
grid. The dispersion sigma_z of our photometric redshifts with respect to
spectroscopic redshifts is sigma_z=0.08 and 0.24 for z2, respectively,
which are smaller than the corresponding values (sigma_z=0.09 and 0.45) by
Fernandez-Soto et al. Improvement is significant, especially in z>2. This is
due to smaller systematic errors which are largely reduced mainly by including
three opacities due to intergalactic HI clouds. We discuss redshift
distribution N(z) and cosmic star formation rate based on our new photometric
redshifts.Comment: 24 pages including 16 eps figures; accepted for publication in Ap
Far Ultraviolet Spectroscopic Explorer Survey of Magellanic Cloud Supernova Remnants
We report the progress to date from an ongoing unbiased ultraviolet survey of
supernova remnants in the Magellanic Clouds using the Far Ultraviolet
Spectroscopic Explorer (FUSE) satellite. This survey is obtaining spectra of a
random large sample of Magellanic Cloud supernova remnants with a broad range
of radio, optical, and X-ray properties. To date, 39 objects have been observed
in the survey (38 in the LMC and one in the SMC) and 15 have been detected, a
detection rate of nearly 40%. Our survey has nearly tripled the number of
UV-detected SNRs in the Magellanic Clouds (from 8 to 22). Because of the
diffuse source sensitivity of FUSE, upper limits on non-detected objects are
quite sensitive in many cases. Estimated total luminosities in O~VI span a
broad range from considerably brighter to many times fainter than the inferred
soft X-ray luminosities, indicating that O~VI can be an important and largely
unrecognized coolant in certain objects. We compare the optical and X-ray
properties of the detected and non-detected objects but do not find a simple
indicator for ultraviolet detectability. Non-detections may be due to
clumpiness of the emission, high foreground extinction, slow shocks whose
emission gets attenuated by the Magellanic interstellar medium, or a
combination of these effects.Comment: 34 pages, 26 figures in 8 separate JPG figure files; the
characteristics of individual detected supernova remnants are summarized in
an Appendi
Continuum and Emission-Line Properties of Broad Absorption Line Quasars
We investigate the continuum and emission-line properties of 224 broad
absorption line quasars (BALQSOs) with 0.9<z<4.4 drawn from the Sloan Digital
Sky Survey (SDSS) Early Data Release (EDR), which contains 3814 bona fide
quasars. We find that low-ionization BALQSOs (LoBALs) are significantly
reddened as compared to normal quasars, in agreement with previous work.
High-ionization BALQSOs (HiBALs) are also more reddened than the average
nonBALQSO. Assuming SMC-like dust reddening at the quasar redshift, the amount
of reddening needed to explain HiBALs is E(B-V)~0.023 and LoBALs is
E(B-V)~0.077 (compared to the ensemble average of the entire quasar sample). We
find that there are differences in the emission-line properties between the
average HiBAL, LoBAL, and nonBAL quasar. These differences, along with
differences in the absorption line troughs, may be related to intrinsic quasar
properties such as the slope of the intrinsic (unreddened) continuum; more
extreme absorption properties are correlated with bluer intrinsic continua.
Despite the differences among BALQSO sub-types and nonBALQSOs, BALQSOs appear
to be drawn from the same parent population as nonBALQSOs when both are
selected by their UV/optical properties. We find that the overall fraction of
traditionally defined BALQSOs, after correcting for color-dependent selection
effects due to different SEDs of BALQSO and nonBALQSOs, is 13.4+/-1.2% and
shows no significant redshift dependence for 1.7<z<3.45. After a rough
completeness correction for the effects of dust extinction, we find that
approximately one in every six quasars is a BALQSO.Comment: 35 pages, 11 figures (1 color), 1 table; accepted by A
Bayesian analysis of exoplanet and binary orbits
We introduce BASE (Bayesian astrometric and spectroscopic exoplanet detection
and characterisation tool), a novel program for the combined or separate
Bayesian analysis of astrometric and radial-velocity measurements of potential
exoplanet hosts and binary stars. The capabilities of BASE are demonstrated
using all publicly available data of the binary Mizar A.Comment: Accepted for publication in Astronomy & Astrophysic
Discovery of a Radio-Selected z ~ 6 Quasar
We present the discovery of only the second radio-selected, z ~ 6 quasar. We
identified SDSS J222843.54+011032.2 (z=5.95) by matching the optical detections
of the deep Sloan Digital Sky Survey (SDSS) Stripe 82 with their radio
counterparts in the Stripe82 VLA Survey. We also matched the
Canadian-France-Hawaiian Telescope Legacy Survey Wide (CFHTLS Wide) with the
Faint Images of the Radio Sky at Twenty-cm (FIRST) survey but have yet to find
any z ~ 6 quasars in this survey area. The discovered quasar is
optically-faint, z = 22.3 and M_{1450} ~ -24.5, but radio-bright, with a flux
density of f = 0.31mJy and a radio-loudness of R ~ 1100 (where
R = f_{5GHz}/f_{2500}). The i-z color of the discovered quasar places it
outside the color selection criteria for existing optical surveys. We conclude
by discussing the need for deeper wide-area radio surveys in the context of
high-redshift quasars.Comment: 20 pages, 6 figures, and ApJ accepte
Air Traffic Management Technology Demonstration-1 Concept of Operations (ATD-1 ConOps)
The operational goal of the ATD-1 ConOps is to enable aircraft, using their onboard FMS capabilities, to fly Optimized Profile Descents (OPDs) from cruise to the runway threshold at a high-density airport, at a high throughput rate, using primarily speed control to maintain in-trail separation and the arrival schedule. The three technologies in the ATD-1 ConOps achieve this by calculating a precise arrival schedule, using controller decision support tools to provide terminal controllers with speeds for aircraft to fly to meet times at a particular meter points, and onboard software providing flight crews with speeds for the aircraft to fly to achieve a particular spacing behind preceding aircraft
Air Traffic Management Technology Demonstration-1 Concept of Operations (ATD-1 ConOps), Version 2.0
This document is an update to the operations and procedures envisioned for NASA s Air Traffic Management (ATM) Technology Demonstration #1 (ATD-1). The ATD-1 Concept of Operations (ConOps) integrates three NASA technologies to achieve high throughput, fuel-efficient arrival operations into busy terminal airspace. They are Traffic Management Advisor with Terminal Metering (TMA-TM) for precise time-based schedules to the runway and points within the terminal area, Controller-Managed Spacing (CMS) decision support tools for terminal controllers to better manage aircraft delay using speed control, and Flight deck Interval Management (FIM) avionics and flight crew procedures to conduct airborne spacing operations. The ATD-1 concept provides de-conflicted and efficient operations of multiple arrival streams of aircraft, passing through multiple merge points, from top-of-descent (TOD) to the Final Approach Fix. These arrival streams are Optimized Profile Descents (OPDs) from en route altitude to the runway, using primarily speed control to maintain separation and schedule. The ATD-1 project is currently addressing the challenges of integrating the three technologies, and their implantation into an operational environment. The ATD-1 goals include increasing the throughput of high-density airports, reducing controller workload, increasing efficiency of arrival operations and the frequency of trajectory-based operations, and promoting aircraft ADS-B equipage
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