scholarly journals Taxonomic classification of asteroids based on MOVIS near-infrared colors

2018 ◽  
Vol 617 ◽  
pp. A12 ◽  
Author(s):  
M. Popescu ◽  
J. Licandro ◽  
J. M. Carvano ◽  
R. Stoicescu ◽  
J. de León ◽  
...  
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Probabilistic Method ◽  
Sloan Digital Sky Survey ◽  
Taxonomic Classification ◽  
Wide Field ◽  
Probabilistic Algorithms ◽  
Frequency Distributions ◽  
Object Based

Context. The MOVIS catalog contains the largest set of near-infrared (NIR) colors for solar system objects. These data were obtained from the observations performed by VISTA-VHS survey using the Y, J, H, and Ks filters. The taxonomic classification of objects in this catalog allows us to obtain large-scale distributions for the asteroidal population, to study faint objects, and to select targets for detailed spectral investigations. Aims. We aim to provide a taxonomic classification for asteroids observed by VISTA-VHS survey. We derive a method for assigning a compositional type to an object based on its (Y − J), (J − Ks), and (H − Ks) colors. Methods. We present a taxonomic classification for 18 265 asteroids from the MOVIS catalog, using a probabilistic method and the k-nearest neighbors algorithm. Because our taxonomy is based only on NIR colors, several classes from Bus-DeMeo were clustered into groups and a slightly different notation was used: i.e., the superscript indicates that the classification was obtained based on the NIR colors and the subscript indicates possible misidentifications with other types. Our results are compared with the information provided by the Sloan Digital Sky Survey (SDSS) and Wide-field Infrared Survey Explorer (WISE). Results. The two algorithms used in this study give a taxonomic type for all objects having at least (Y − J) and (J − Ks) observed colors. A final classification is reported for a set of 6496 asteroids based on the criteria that kNN and probabilistic algorithms gave the same result, and the color errors are within the limits (Y − J)err ≤ 0.118 and (J − Ks)err ≤ 0.136. This set includes 144 bodies classified as Bkni, 613 as Cni, 197 as Cgxni, 91 as Xtni, 440 as Dsni, 665 as Klni, 233 as Adni, 3315 as Sni, and 798 as Vni. We report the albedo distribution for each taxonomic group and we compute new median values for the main types. We found that V-type and A-type candidates have identical size frequency distributions, but V types are five times more common than A types. Several particular cases, such as the A-type asteroid (11616) 1996 BQ2 and the S-type (3675) Kematsch, both in the Cybele population, are discussed.

scholarly journals Land Cover Classification of Nine Perennial Crops Using Sentinel-1 and -2 Data

2019 ◽  
Vol 12 (1) ◽  
pp. 96 ◽  
Author(s):  
James Brinkhoff ◽  
Justin Vardanega ◽  
Andrew J. Robson
Keyword(s):  
Land Cover ◽  
Large Scale ◽  
Satellite Image ◽  
Resource Planning ◽  
Support Vector ◽  
Perennial Crop ◽  
Perennial Crops ◽  
Object Based ◽  
Rbf Kernel

Land cover mapping of intensive cropping areas facilitates an enhanced regional response to biosecurity threats and to natural disasters such as drought and flooding. Such maps also provide information for natural resource planning and analysis of the temporal and spatial trends in crop distribution and gross production. In this work, 10 meter resolution land cover maps were generated over a 6200 km2 area of the Riverina region in New South Wales (NSW), Australia, with a focus on locating the most important perennial crops in the region. The maps discriminated between 12 classes, including nine perennial crop classes. A satellite image time series (SITS) of freely available Sentinel-1 synthetic aperture radar (SAR) and Sentinel-2 multispectral imagery was used. A segmentation technique grouped spectrally similar adjacent pixels together, to enable object-based image analysis (OBIA). K-means unsupervised clustering was used to filter training points and classify some map areas, which improved supervised classification of the remaining areas. The support vector machine (SVM) supervised classifier with radial basis function (RBF) kernel gave the best results among several algorithms trialled. The accuracies of maps generated using several combinations of the multispectral and radar bands were compared to assess the relative value of each combination. An object-based post classification refinement step was developed, enabling optimization of the tradeoff between producers’ accuracy and users’ accuracy. Accuracy was assessed against randomly sampled segments, and the final map achieved an overall count-based accuracy of 84.8% and area-weighted accuracy of 90.9%. Producers’ accuracies for the perennial crop classes ranged from 78 to 100%, and users’ accuracies ranged from 63 to 100%. This work develops methods to generate detailed and large-scale maps that accurately discriminate between many perennial crops and can be updated frequently.

scholarly journals The HETDEX Instrumentation: Hobby–Eberly Telescope Wide-field Upgrade and VIRUS

2021 ◽  
Vol 162 (6) ◽  
pp. 298
Author(s):  
Gary J. Hill ◽  
Hanshin Lee ◽  
Phillip J. MacQueen ◽  
Andreas Kelz ◽  
Niv Drory ◽  
...  
Keyword(s):  
Dark Energy ◽  
Large Scale ◽  
Near Infrared ◽  
Cosmological Parameters ◽  
Resolving Power ◽  
Wide Field ◽  
Low Resolution ◽  
Integral Field Spectrograph ◽  
Optical Astronomy ◽  
Integral Field

Abstract The Hobby–Eberly Telescope (HET) Dark Energy Experiment (HETDEX) is undertaking a blind wide-field low-resolution spectroscopic survey of 540 deg2 of sky to identify and derive redshifts for a million Lyα-emitting galaxies in the redshift range 1.9 < z < 3.5. The ultimate goal is to measure the expansion rate of the universe at this epoch, to sharply constrain cosmological parameters and thus the nature of dark energy. A major multiyear Wide-Field Upgrade (WFU) of the HET was completed in 2016 that substantially increased the field of view to 22′ diameter and the pupil to 10 m, by replacing the optical corrector, tracker, and Prime Focus Instrument Package and by developing a new telescope control system. The new, wide-field HET now feeds the Visible Integral-field Replicable Unit Spectrograph (VIRUS), a new low-resolution integral-field spectrograph (LRS2), and the Habitable Zone Planet Finder, a precision near-infrared radial velocity spectrograph. VIRUS consists of 156 identical spectrographs fed by almost 35,000 fibers in 78 integral-field units arrayed at the focus of the upgraded HET. VIRUS operates in a bandpass of 3500−5500 Å with resolving power R ≃ 800. VIRUS is the first example of large-scale replication applied to instrumentation in optical astronomy to achieve spectroscopic surveys of very large areas of sky. This paper presents technical details of the HET WFU and VIRUS, as flowed down from the HETDEX science requirements, along with experience from commissioning this major telescope upgrade and the innovative instrumentation suite for HETDEX.

scholarly journals Mesospheric bores at southern midlatitudes observed by ISS-IMAP/VISI: a first report of an undulating wave front

2018 ◽  
Vol 18 (22) ◽  
pp. 16399-16407 ◽  
Author(s):  
Yuta Hozumi ◽  
Akinori Saito ◽  
Takeshi Sakanoi ◽  
Atsushi Yamazaki ◽  
Keisuke Hosokawa
Keyword(s):  
Wave Front ◽  
Large Scale ◽  
Near Infrared ◽  
Inversion Layer ◽  
Space Station ◽  
Temperature Inversion ◽  
Wide Field ◽  
Broadband Emission ◽  
The Difference ◽  
Spectral Imager

Abstract. Large-scale spatial structures of mesospheric bores were observed by the Visible and near-Infrared Spectral Imager (VISI) of the ISS-IMAP mission (Ionosphere, Mesosphere, upper Atmosphere and Plasmasphere mapping mission from the International Space Station) in the mesospheric O2 airglow at 762 nm wavelength. Two mesospheric bore events in southern midlatitudes are reported in this paper: one event at 48–54∘ S, 10–20∘ E on 9 July 2015 and the other event at 35–43∘ S, 24∘ W–1∘ E on 7 May 2013. For the first event, the temporal evolution of the mesospheric bore was investigated from the difference of two observations in consecutive passes. The estimated eastward speed of the bore is 100 m s−1. The number of trailing waves increased with a rate of 3.5 waves h−1. Anticlockwise rotation with a speed of 20∘ h−1 was also recognized. These parameters are similar to those reported by previous studies based on ground-based measurements, and the similarity supports the validity of VISI observation for mesospheric bores. For the second event, VISI captured a mesospheric bore with a large-scale and undulating wave front. The horizontal extent of the wave front was 2200 km. The long wave front undulated with a wavelength of 1000 km. The undulating wave front is a new feature of mesospheric bores revealed by the wide field of view of VISI. We suggest that nonuniform bore propagating speed due to inhomogeneous background ducting structure might be a cause of the undulation of the wave front. Temperature measurements from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) onboard the Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) satellite indicated that bores of both events were ducted in a temperature inversion layer.

scholarly journals The Apache Point Observatory Galactic Evolution Experiment (APOGEE)

2009 ◽  
Vol 5 (S262) ◽  
pp. 428-429
Author(s):  
Ricardo P. Schiavon ◽  
Steven R. Majewski
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Milky Way ◽  
Galactic Evolution ◽  
Sloan Digital Sky Survey ◽  
Elemental Abundances ◽  
Sky Survey ◽  
The Galaxy ◽  
Evolution Experiment ◽  
Under Construction

AbstractThe Apache Point Observatory Galactic Evolution Experiment (APOGEE) is a large scale, high-resolution, near-infrared spectroscopic survey of Milky Way stellar populations and one of the four experiments in the Sloan Digital Sky Survey III (SDSS-III). APOGEE will be based on a new multi-fiber cryogenic spectrograph, currently under construction, expected to begin survey observations on the 2.5 m Sloan telescope in the Spring of 2011. APOGEE will measure high-precision radial velocities and elemental abundances for ~15 elements for ~ 105 stars, and is expected to shed new light on the processes that led to the formation of the Galaxy.

scholarly journals AN EXTREMELY DEEP, WIDE-FIELD NEAR-INFRARED SURVEY: BRIGHT GALAXY COUNTS AND LOCAL LARGE SCALE STRUCTURE

2009 ◽  
Vol 186 (1) ◽  
pp. 94-110 ◽  
Author(s):  
R. C. Keenan ◽  
L. Trouille ◽  
A. J. Barger ◽  
L. L. Cowie ◽  
W.-H. Wang
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Wide Field ◽  
Bright Galaxy ◽  
Infrared Survey

scholarly journals The distance to M31 in the era of precision cosmology

2012 ◽  
Vol 8 (S289) ◽  
pp. 235-235
Author(s):  
David Valls-Gabaud
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Hubble Space Telescope ◽  
Three Dimensional ◽  
Eclipsing Binaries ◽  
Wide Field ◽  
Acoustic Oscillations ◽  
Data Set ◽  
Red Giant ◽  
Precision Cosmology

AbstractWith the advent of precision cosmology, where distances out to redshifts z < 0.6 can be measured to 2% precision on the basis of baryon acoustic oscillations, it appears essential to establish an accurate calibration of the primary and secondary indicators of the cosmological distance ladder. Here we review recent attempts at anchoring M31 very accurately using three independent methods, and discuss in detail the systematics that affect each. Two double-lined eclipsing binaries yield a distance to M31 which is precise to 4%. New Bayesian methods have been applied to determine the tip of the red-giant branch, even in sparsely populated colour–magnitude diagrams, and provide unique insights in the context of a precise three-dimensional distribution of the satellites in the M31 system. Over 2500 Cepheids have been identified in large-scale multi-colour surveys of M31, the largest homogeneous data set thus far obtained for any galaxy. A subset of 68 with periods longer than 10 days have been observed with the Wide-Field Camera 3 on board the Hubble Space Telescope, yielding the tightest-ever near-infrared period–luminosity relation, with a mean distance error of 1%. Combined with other measurements, the distance to M31 is now measured with a precision of 3%. Forthcoming improvements, and their implications, are also discussed.

scholarly journals Transient-optimised real-bogus classification with Bayesian Convolutional Neural Networks — sifting the GOTO candidate stream

2021 ◽  
Author(s):  
T L Killestein ◽  
J Lyman ◽  
D Steeghs ◽  
K Ackley ◽  
M J Dyer ◽  
...  
Keyword(s):  
Large Scale ◽  
Data Driven ◽  
Wide Field ◽  
Data Generation ◽  
Training Set ◽  
Transient Sources ◽  
Data Driven Approach ◽  
Model Training ◽  
Difference Imaging

Abstract Large-scale sky surveys have played a transformative role in our understanding of astrophysical transients, only made possible by increasingly powerful machine learning-based filtering to accurately sift through the vast quantities of incoming data generated. In this paper, we present a new real-bogus classifier based on a Bayesian convolutional neural network that provides nuanced, uncertainty-aware classification of transient candidates in difference imaging, and demonstrate its application to the datastream from the GOTO wide-field optical survey. Not only are candidates assigned a well-calibrated probability of being real, but also an associated confidence that can be used to prioritise human vetting efforts and inform future model optimisation via active learning. To fully realise the potential of this architecture, we present a fully-automated training set generation method which requires no human labelling, incorporating a novel data-driven augmentation method to significantly improve the recovery of faint and nuclear transient sources. We achieve competitive classification accuracy (FPR and FNR both below 1%) compared against classifiers trained with fully human-labelled datasets, whilst being significantly quicker and less labour-intensive to build. This data-driven approach is uniquely scalable to the upcoming challenges and data needs of next-generation transient surveys. We make our data generation and model training codes available to the community.

scholarly journals Object-Based Classification of Ikonos Imagery for Mapping Large-Scale Vegetation Communities in Urban Areas

Sensors ◽  
2007 ◽  
Vol 7 (11) ◽  
pp. 2860-2880 ◽  
Author(s):  
Renaud Mathieu ◽  
Jagannath Aryal ◽  
Albert Chong
Keyword(s):  
Urban Areas ◽  
Large Scale ◽  
Vegetation Communities ◽  
Object Based

scholarly journals The near and mid-infrared photometric properties of known redshift z ≥ 5 quasars

2020 ◽  
Vol 494 (1) ◽  
pp. 789-803 ◽  
Author(s):  
Nicholas P Ross ◽  
Nicholas J G Cross
Keyword(s):  
Near Infrared ◽  
Signal To Noise Ratio ◽  
High Redshift ◽  
Infrared Camera ◽  
Sloan Digital Sky Survey ◽  
Wide Field ◽  
Photometric Variability ◽  
Infrared Telescope ◽  
Black Hole Accretion ◽  
Very High

ABSTRACT We assemble a catalogue of 488 spectroscopically confirmed very high (z ≥ 5.00) redshift quasars (VHzQ) and report their near- (ZYJHKs/K) and mid- (WISE W1234) infrared properties. 97 per cent of the VHzQ sample is detected in one or more near-infrared (NIR) band, with lack of coverage rather than lack of depth being the reason for the non-detections. 389 (80 per cent) of the very high redshift quasars are detected at 3.4 μm in the W1 band from the unWISE catalogue and all of the z ≥ 7 quasars are detected in both unWISE W1 and W2. Using archival Wide Field Camera (WFCAM)/United Kingdom Infrared Telescope (UKIRT) and VISTA Infrared Camera (VIRCAM)/Visible and Infrared Survey Telescope for Astronomy (VISTA) data we check for photometric variability that might be expected from super-Eddington accretion. We find 28 of the quasars have sufficient NIR measurements and signal-to-noise ratio to look for variability. Weak variability was detected in multiple bands of Sloan Digital Sky Survey (SDSS) J0959+0227, and very marginally in the Y-band of MMT J0215-0529. Only one quasar, SDSS J0349+0034, shows significant differences between WFCAM and VISTA magnitudes in one band. With supermassive black hole accretion likely to be redshift invariant up to very high redshift, further monitoring of these sources is warranted. All the data, analysis codes and plots used and generated here can be found at: github.com/d80b2t/VHzQ.

scholarly journals The Apache Point Observatory Galactic Evolution Experiment (APOGEE) in Sloan Digital Sky Survey III (SDSS-III)

2009 ◽  
Vol 5 (S265) ◽  
pp. 480-481 ◽  
Author(s):  
Steven R. Majewski ◽  
John C. Wilson ◽  
Fred Hearty ◽  
Ricardo R. Schiavon ◽  
Michael F. Skrutskie
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Milky Way ◽  
Chemical Species ◽  
Galactic Evolution ◽  
Sloan Digital Sky Survey ◽  
Red Giants ◽  
Sky Survey ◽  
Evolution Experiment ◽  
Novel Design

AbstractThe Apache Point Observatory Galactic Evolution Experiment (APOGEE) is a large-scale, near-infrared (H-band), high-resolution (R ~ 30,000), high S/N (≳100) spectroscopic survey of Milky Way stellar populations. APOGEE will operate from 1.51–1.68μm, a region that includes useful absorption lines from at least fifteen chemical species including α, odd-Z, and iron peak elements. The APOGEE instrument has a novel design featuring 300 science fibers feeding light to a mosaiced VPH grating and a six-element camera encased in a liquid nitrogen-cooled cryostat. A three year bright-time observing campaign will enable APOGEE to observe approximately 100,000 red giants across the Galactic bulge, disk and halo.

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