We report on the development of neural networks for generating readings from Telescope Array’s surface detectors with the largest registered integral signal. To achieve this goal, we implemented ...generative Wasserstein adversarial networks with the gradient penalty. The data used to train the model was generated using the Monte Carlo method. We obtained visually similar data which are consistent with the physics of the underlying processes. The anomaly search method can be employed to identify discrepancies between real and simulated data, as well as to introduce a quantitative measure of similarity between the real detector readings and those generated by the neural network’s readings.
The Telescope Array (TA) experiment is the largest Ultra-High Energy Cosmic Ray (UHECR) observatory in the northern hemisphere, located in the west Utah desert. The recent results of the measurements ...for the energy spectrum, composition and anisotropy of UHECRs from the TA seven years observation are presented. In addition, the design and current status of the TA extensions, TA×4 and TALE, is discussed.
•Ceres, the second target for the DAWN mission, from adaptive optics images at Keck and the VLT over ten years is found to be an oblate spheroid with diameters of 967X967X892, with an uncertainty of ...10 km in each dimension.•Its rotational pole is found to lie within 3 degrees of RA Dec=287+64.•The soft terminator (‘terminator fading’) is measurable in the high resolution images.
The dwarf planet (1) Ceres, the largest object between Mars and Jupiter, is the target of the NASA Dawn mission, and we seek a comprehensive description of the spin-axis orientation and dimensions of Ceres in order to support the early science operations at the rendezvous in 2015. We have obtained high-angular resolution images using adaptive optics cameras at the W.M. Keck Observatory and the ESO VLT over ten dates between 2001 and 2010, confirming that the shape of Ceres is well described by an oblate spheroid. We derive equatorial and polar diameters of 967±10km and 892±10km, respectively, for a model that includes fading of brightness towards the terminator, presumably linked to limb darkening. These dimensions lie between values derived from a previous analysis of a subset of these images obtained at Keck by Carry et al. (Carry et al. 2008. Astron. Astrophys. 478 (4), 235–244) and a study of Hubble Space Telescope observations (Thomas et al. 2005. Nature 437, 224–226). Although the dimensions are 1–2% smaller than those found from the HST, the oblateness is similar.
We find the spin-vector coordinates of Ceres to lie at (287°, +64°) in equatorial EQJ2000 reference frame (346°, +82° in ecliptic ECJ2000 coordinates), yielding a small obliquity of 3°. While this is in agreement with the aforementioned studies, we have improved the accuracy of the pole determination, which we set at a 3° radius.
The Telescope Array experiment studies ultra high energy cosmic rays using a hybrid detector. Fluorescence telescopes measure the longitudinal development of the extensive air shower generated when a ...primary cosmic ray particle interacts with the atmosphere. Meanwhile, scintillator detectors measure the lateral distribution of secondary shower particles that hit the ground. The Middle Drum (MD) fluorescence telescope station consists of 14 telescopes from the High Resolution Fly’s Eye (HiRes) experiment, providing a direct link back to the HiRes measurements. Using the scintillator detector data in conjunction with the telescope data improves the geometrical reconstruction of the showers significantly, and hence, provides a more accurate reconstruction of the energy of the primary particle. The Middle Drum hybrid spectrum is presented and compared to that measured by the Middle Drum station in monocular mode. Further, the hybrid data establishes a link between the Middle Drum data and the surface array. A comparison between the Middle Drum hybrid energy spectrum and scintillator Surface Detector (SD) spectrum is also shown.
The Telescope Array (TA) consists of an array of surface detectors (SD) covering 700 km2 in area and three fluorescence detector (FD) stations and explores the origin of ultra-high-energy cosmic ...rays. We found evidence for a cosmic-ray hotspot, which is the sky area of emitting more highest-energy cosmic rays than other area. To confirm what the origin of the hotspot is, we proposed the TAx4, which would quadruple the TA. From around 1015.5 eV to 1018 eV, we expect the transition from galactic cosmic rays to extra-galactic cosmic rays. The TALE (TA Low-Energy extension) FD has been fully operational and the TALE SDs have been operating partially. We confirmed two breaks at 1016.3 eV and 1017.3 eV in the energy spectrum measured with the TALE FD, and we proposed to construct remaining TALE SDs to improve the resolution of the shower maximum depth (Xmax) measured with the TALE FD for composition identification. Both five-year proposals for TAx4 SD and TALE SD were funded independently in the spring of 2015. Here we present the status of these projects including NICHE (Non-Imaging CHErenkov detector array) that aims at energy extension down to 1015 eV (Knee region).
ABSTRACT
The
i
-band observing conditions at Dome A on the Antarctic plateau have been investigated using data acquired during 2008 with the Chinese Small Telescope Array. The sky brightness, ...variations in atmospheric transparency, cloud cover, and the presence of aurorae are obtained from these images. The median sky brightness of moonless clear nights is 20.5 mag arcsec
−2
in the SDSS
i
band at the south celestial pole (which includes a contribution of about 0.06 mag from diffuse Galactic light). The median over all Moon phases in the Antarctic winter is about 19.8 mag arcsec
−2
. There were no thick clouds in 2008. We model contributions of the Sun and the Moon to the sky background to obtain the relationship between the sky brightness and transparency. Aurorae are identified by comparing the observed sky brightness to the sky brightness expected from this model. About 2% of the images are affected by relatively strong aurorae.
In this paper, the impact of random synchronization errors on the performance of ground-based telescope array receivers for an inter-planetary optical deep-space communication (ODSC) link is ...investigated. An adaptive method based on Kalman filters is developed for the synchronization and combination of different telescope signals in the array. An end-to-end simulation platform for ODSC link between Earth and planet Mars is implemented that incorporates pulse-position modulation (PPM), direct-detection array receivers, and photon-counting detectors. The effects of atmospheric turbulence and background noise are also modeled. The performance of array receivers is evaluated in terms of probability of symbol error and achievable data rates. The simulation results show that the Kalman filter-based synchronization scheme keeps the synchronization induced power losses to less than 1dB. The analysis also shows that in the worst-case operational scenario and presence of random synchronization errors, an array consisting of hundred, 1m telescopes performs almost similar to a single 10m telescope. Hence, the degradation in the combined signal due to synchronization errors places a minor limitation on the number of telescopes in a telescope array receiver consisting of up to 100 telescope elements.
The extremely low flux of ultra-high energy cosmic rays (UHECR) makes their direct observation by orbital experiments practically impossible. For this reason all current and planned UHECR experiments ...detect cosmic rays indirectly by observing the extensive air showers (EAS) initiated by cosmic ray particles in the atmosphere. The world largest statistics of the ultra-high energy EAS events is recorded by the networks of surface stations. In this paper we consider a novel approach for reconstruction of the arrival direction of the primary particle based on the deep convolutional neural network. The latter is using raw time-resolved signals of the set of the adjacent trigger stations as an input. The Telescope Array (TA) Surface Detector (SD) is an array of 507 stations, each containing two layers plastic scintillator with an area of 3 m2. The training of the model is performed with the Monte-Carlo dataset. It is shown that within the Monte-Carlo simulations, the new approach yields better resolution than the traditional reconstruction method based on the fitting of the EAS front. The details of the network architecture and its optimization for this particular task are discussed.
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