367 research outputs found
Image Analysis for Facility Siting: a Comparison of Lowand High-altitude Image Interpretability for Land Use/land Cover Mapping
For two test sites in Pennsylvania the interpretability of commercially acquired low-altitude and existing high-altitude aerial photography are documented in terms of time, costs, and accuracy for Anderson Level II land use/land cover mapping. Information extracted from the imagery is to be used in the evaluation process for siting energy facilities. Land use/land cover maps were drawn at 1:24,000 scale using commercially flown color infrared photography obtained from the United States Geological Surveys' EROS Data Center. Detailed accuracy assessment of the maps generated by manual image analysis was accomplished employing a stratified unaligned adequate class representation. Both 'area-weighted' and 'by-class' accuracies were documented and field-verified. A discrepancy map was also drawn to illustrate differences in classifications between the two map scales. Results show that the 1:24,000 scale map set was more accurate (99% to 94% area-weighted) than the 1:62,500 scale set, especially when sampled by class (96% to 66%). The 1:24,000 scale maps were also more time-consuming and costly to produce, due mainly to higher image acquisition costs
Ks band secondary eclipses of WASP-19b and WASP-43b with the Anglo-Australian Telescope
We report new Ks band secondary eclipse observations for the hot-Jupiters
WASP-19b and WASP-43b. Using the IRIS2 infrared camera on the Anglo-Australian
Telescope (AAT), we measured significant secondary eclipses for both planets,
with depths of 0.287 -0.020/+0.020% and 0.181 -0.027/+0.027% for WASP-19b and
WASP-43b respectively. We compare the observations to atmosphere models from
the VSTAR line-by-line radiative transfer code, and examine the effect of C/O
abundance, top layer haze, and metallicities on the observed spectra. We
performed a series of signal injection and recovery exercises on the observed
light curves to explore the detection thresholds of the AAT+IRIS2 facility. We
find that the optimal photometric precision is achieved for targets brighter
than Kmag = 9, for which eclipses as shallow as 0.05% are detectable at >5
sigma significance.Comment: Accepted for publication in MNRAS, 13 pages, 10 figure
Prime agricultural land monitoring and assessment component of the California Integrated Remote Sensing System
The use of digital LANDSAT techniques for monitoring agricultural land use conversions was studied. Two study areas were investigated: one in Ventura County and the other in Fresno County (California). Ventura test site investigations included the use of three dates of LANDSAT data to improve classification performance beyond that previously obtained using single data techniques. The 9% improvement is considered highly significant. Also developed and demonstrated using Ventura County data is an automated cluster labeling procedure, considered a useful example of vertical data integration. Fresno County results for a single data LANDSAT classification paralleled those found in Ventura, demonstrating that the urban/rural fringe zone of most interest is a difficult environment to classify using LANDSAT data. A general raster to vector conversion program was developed to allow LANDSAT classification products to be transferred to an operational county level geographic information system in Fresno
WISE J163940.83-684738.6: A Y Dwarf identified by Methane Imaging
We have used methane imaging techniques to identify the near-infrared
counterpart of the bright WISE source WISEJ163940.83-684738.6. The large proper
motion of this source (around 3.0arcsec/yr) has moved it, since its original
WISE identification, very close to a much brighter background star -- it
currently lies within 1.5" of the J=14.90+-0.04 star 2MASS16394085-6847446.
Observations in good seeing conditions using methane sensitive filters in the
near-infrared J-band with the FourStar instrument on the Magellan 6.5m Baade
telescope, however, have enabled us to detect a near-infrared counterpart. We
have defined a photometric system for use with the FourStar J2 and J3 filters,
and this photometry indicates strong methane absorption, which unequivocally
identifies it as the source of the WISE flux. Using these imaging observations
we were then able to steer this object down the slit of the FIRE spectrograph
on a night of 0.6" seeing, and so obtain near-infrared spectroscopy confirming
a Y0-Y0.5 spectral type. This is in line with the object's
near-infrared-to-WISE J3--W2 colour. Preliminary astrometry using both WISE and
FourStar data indicates a distance of 5.0+-0.5pc and a substantial tangential
velocity of 73+-8km/s. WISEJ163940.83-684738.6 is the brightest confirmed Y
dwarf in the WISE W2 passband and its distance measurement places it amongst
the lowest luminosity sources detected to date.Comment: Accepted for publication in The Astrophysical Journal, 20 September
201
The amplitude of solar oscillations using stellar techniques
The amplitudes of solar-like oscillations depend on the excitation and
damping, both of which are controlled by convection. Comparing observations
with theory should therefore improve our understanding of the underlying
physics. However, theoretical models invariably compute oscillation amplitudes
relative to the Sun, and it is therefore vital to have a good calibration of
the solar amplitude using stellar techniques. We have used daytime spectra of
the Sun, obtained with HARPS and UCLES, to measure the solar oscillations and
made a detailed comparison with observations using the BiSON helioseismology
instrument. We find that the mean solar amplitude measured using stellar
techniques, averaged over one full solar cycle, is 18.7 +/- 0.7 cm/s for the
strongest radial modes (l=0) and 25.2 +/- 0.9 cm/s for l=1. In addition, we use
simulations to establish an equation that estimates the uncertainty of
amplitude measurements that are made of other stars, given that the mode
lifetime is known. Finally, we also give amplitudes of solar-like oscillations
for three stars that we measured from a series of short observations with HARPS
(gamma Ser, beta Aql and alpha For), together with revised amplitudes for five
other stars for which we have previously published results (alpha Cen A, alpha
Cen B, beta Hyi, nu Ind and delta Pav).Comment: 8 pages, accepted by ApJ. Minor wording changes and added a referenc
56Ni dredge-up in the type IIp Supernova 1995V
We present contemporary infrared and optical spectra of the plateau type II
SN 1995V in NGC 1087 covering four epochs, approximately 22 to 84 days after
shock breakout. The data show, for the first time, the infrared spectroscopic
evolution during the plateau phase of a typical type II event. In the optical
region P Cygni lines of the Balmer series and of metals lines were identified.
The infrared (IR) spectra were largely dominated by the continuum, but P Cygni
Paschen lines and Brackett gamma lines were also clearly seen. The other
prominent IR features are confined to wavelengths blueward of 11000 \AA and
include Sr II 10327, Fe II 10547, C I 10695 and He I 10830 \AA. We demonstrate
the presence of He I 10830 \AA on days 69 and 85. The presence of this line at
such late times implies re-ionisation. A likely re-ionising mechanism is
gamma-ray deposition following the radioactive decay of 56Ni. We examine this
mechanism by constructing a spectral model for the He I 10830 \AA line based on
explosion model s15s7b2f of Weaver & Woosley (1993). We find that this does not
generate the observed line owing to the confinement of the 56Ni to the central
zones of the ejecta. In order to reproduce the He I line, it was necessary to
introduce additional upward mixing of the 56Ni, with 10^{-5} of the total
nickel mass reaching above the helium photosphere. In addition, we argue that
the He I line-formation region is likely to have been in the form of pure
helium clumps in the hydrogen envelope.Comment: Accepted for publication in MNRAS, 32 pages including 11 figures
(uses psfig.sty - included
Irrigated lands assessment for water management: Technique test
A procedure for estimating irrigated land using full frame LANDSAT imagery was demonstrated. Relatively inexpensive interpretation of multidate LANDSAT photographic enlargements was used to produce a map of irrigated land in California. The LANDSAT and ground maps were then linked by regression equations to enable precise estimation of irrigated land area by county, basin, and statewide. Land irrigated at least once in California in 1979 was estimated to be 9.86 million acres, with an expected error of less than 1.75% at the 99% level of confidence. To achieve the same level of error with a ground-only sample would have required 3 to 5 times as many ground sample units statewide. A procedure for relatively inexpensive computer classification of LANDSAT digital data to irrigated land categories was also developed. This procedure is based on ratios of MSS band 7 and 5, and gave good results for several counties in the Central Valley
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