Radio Antenna Array Research Articles

Combinatorial Optimization of Engineering Systems based on Diagrammatic Design

The objectives of the combinatorial optimization of engineering systems based on diagrammatic design are enhancing technical indices of the systems with spatially or temporally distributed elements (e.g., radio-antenna arrays) concerning resolving ability, positioning precision, transmission speed, and performance reliability, using the graphical performance of appropriate algebraic models of the system, such as cyclic difference sets, Galois fields and “Ideal Ring Bundles”. The diagrammatic design provides configuring systems with a smaller number of elements than at present, while upholding or improving on the other significant operating quality indices of the system.

Study on the Performance of the GRANDProto300 Particle Detector Array by Simulation

The Giant Radio Array for Neutrino Detection (GRAND) is a proposed large-scale observatory designed to detect cosmic rays, gamma-rays, and neutrinos with energies exceeding 100 PeV. The GRANDProto300 experiment is proposed as the early stage of the GRAND project, consisting of a hybrid array of radio antennas and scintillator detectors. The latter, as a mature and traditional detector, is used to cross-check the nature of the candidate events selected from radio observations. In this study, we developed a simulation software called G4GRANDProto300, based on the Geant4 software package, to optimize the spacing of the scintillator detector array and to investigate its effective area. The analysis was conducted at various zenith angles under different detector spacings, including 300, 500, 600, 700, and 900 m. Our results indicate that, for large zenith angles used to search for cosmic-ray in the GRAND project, the optimized effective area is with a detector spacing of 500 m. The G4GRANDProto300 software that we developed could be used to further optimize the layout of the particle detector array in future work.

Uncertainties of the 30–408 MHz Galactic emission as a calibration source for radio detectors in astroparticle physics

Context. Arrays of radio antennas have proven to be successful in astroparticle physics with the observation of extensive air showers initiated by high-energy cosmic rays in the Earth’s atmosphere. Accurate determination of the energy scale of the primary particles’ energies requires an absolute calibration of the radio antennas for which, in recent years, the utilization of the Galactic emission as a reference source has emerged as a potential standard. Aims. To apply the “Galactic calibration” a proper estimation of the systematic uncertainties on the prediction of the Galactic emission from sky models is necessary, which we aim to quantify on a global level and for the specific cases of selected radio arrays. We further aim to determine the influence of additional natural radio sources on the Galactic calibration. Methods. We compared seven different sky models that predict the full-sky Galactic emission in the frequency range from 30 to 408 MHz. We made an inventory of the reference maps on which they rely and used the output of the models to determine their global level of agreement. We subsequently took typical sky exposures and the frequency bands of selected radio arrays into account and repeated the comparison for each of them. Finally, we studied and discuss the relative influence of the quiet Sun, the ionosphere, and Jupiter. Results. We find a systematic uncertainty of 14.3% on the predicted power from the Galactic emission, which scales to approximately half of that value as the uncertainty on the determination of the energy of cosmic particles. When looking at the selected radio arrays, the uncertainty on the predicted power varies between 11.7% and 21.5%. The influence of the quiet Sun turns out to be insignificant at the lowest frequencies but increases to a relative contribution of ~30% around 400 MHz.

The depth of the shower maximum of air showers measured with AERA

The Auger Engineering Radio Array (AERA), as part of the Pierre Auger Observatory, is an array of radio antennas probing the nature of ultra-high energy cosmic rays at energies around the transition from Galactic to extra-galactic origin. It measures the MHz radio emission of extensive air showers produced by cosmic rays hitting our atmosphere. The elemental composition of cosmic rays is a crucial piece of information in determining what the sources of cosmic rays are and how cosmic rays are accelerated. This composition can be obtained from the mass-sensitive parameterXmax, the depth of the shower maximum. We reconstructXmaxwith a likelihood analysis, by comparing the measured radio footprint on the ground to an ensemble of footprints from Monte-Carlo CORSIKA/CoREAS air shower simulations. We compare ourXmaxreconstruction with fluorescenceXmaxmeasurements on a per-event basis, a setup unique to the Pierre Auger Observatory, and show the methods to be fully compatible. Furthermore, we extensively validate our reconstruction by identifying and correcting for systematic uncertainties. We determine the resolution of our method as a function of energy and reach a precision better than 15 g cm−2at the highest energies. With a bias-free set of around 600 showers, we find a light to light-mixed composition at energies between 1017.5to 1018.8eV, also in agreement with the Auger fluorescence measurements.

Signal model and event reconstruction for the radio detection of inclined air showers

The detection of inclined air showers (zenith angles θ ≳ 65°) with kilometer-spaced radio-antenna arrays allows measuring cosmic rays at ultra-high energies (E ≲ 1020 eV). Radio and particle detector arrays provide independent measurements of the electromagnetic and muonic shower components of inclined air showers, respectively. Combined, these measurements have a large sensitivity to discriminate between air showers initiated by lighter and heavier cosmic rays. We have developed a precise model of the two-dimensional, highly complex and asymmetric lateral radio-signal distributions of inclined air shower at ground — the “radio-emission footprints”. Our model explicitly describes the dominant geomagnetic emission with a rotationally symmetric lateral distribution function, on top of which additional effects disturb the symmetry. The asymmetries are associated with the interference between the geomagnetic and sub-dominant charge-excess emission as well as with geometrical projection effects, so-called “early-late” effects. Our fully analytic model describes the entire footprint with only two observables: the geometrical distance between the shower impact point at the ground and the shower maximum d max, and the geomagnetic radiation energy E geo. We demonstrate that with this model, the electromagnetic shower energy can be reconstructed by kilometer-spaced antenna arrays with an intrinsic resolution of 5% and a negligible bias.

TAROGE-M: radio antenna array on antarctic high mountain for detecting near-horizontal ultra-high energy air showers

The TAROGE-M radio observatory is a self-triggered antenna array on top of the ∼2700 m high Mt. Melbourne in Antarctica, designed to detect impulsive geomagnetic emission from extensive air showers induced by ultra-high energy (UHE) particles beyond 1017 eV, including cosmic rays, Earth-skimming tau neutrinos, and particularly, the “ANITA anomalous events” (AAE) from near and below the horizon. The six AAE discovered by the ANITA experiment have signal features similar to tau neutrinos but that hypothesis is in tension either with the interaction length predicted by Standard Model or with the flux limits set by other experiments. Their origin remains uncertain, requiring more experimental inputs for clarification.The detection concept of TAROGE-M takes advantage of a high altitude with synoptic view toward the horizon as an efficient signal collector, and the radio quietness as well as strong and near vertical geomagnetic field in Antarctica, enhancing the relative radio signal strength. This approach has a low energy threshold, high duty cycle, and is easy to extend for quickly enlarging statistics. Here we report experimental results from the first TAROGE-M station deployed in January 2020, corresponding to approximately one month of livetime. The station consists of six receiving antennas operating at 180–450 MHz, and can reconstruct source directions of impulsive events with an angular resolution of ∼0.3°, calibrated in situ with a drone-borne pulser system. To demonstrate TAROGE-M's ability to detect UHE air showers, a search for cosmic ray signals in 25.3-days of data together with the detection simulation were conducted, resulting in seven identified candidates. The detected events have a mean reconstructed energy of 0.95-0.31 +0.46 EeV and zenith angles ranging from 25° to 82°, with both distributions agreeing with the simulations, indicating an energy threshold at about 0.3 EeV. The estimated cosmic ray flux at that energy is 1.2-0.9 +0.7 × 10-16 eV-1 km-2 yr-1 sr-1, also consistent with results of other experiments. The TAROGE-M sensitivity to AAEs is approximated by the tau neutrino exposure with simulations, which suggests comparable sensitivity as ANITA's at around 1 EeV energy with a few station-years of operation. These first results verified the station design and performance in a polar and high-altitude environment, and are promising for further discovery of tau neutrinos and AAEs after an extension in the near future.

Radio interferometry applied to the observation of cosmic-ray induced extensive air showers

We developed a radio interferometric technique for the observation of extensive air showers initiated by cosmic particles. In this proof-of-principle study we show that properties of extensive air showers can be derived with high accuracy in a straightforward manner. When time synchronisation below sim 1 ns between different receivers can be achieved, direction reconstruction resolution of < 0.2^circ and resolution on the depth of shower maximum of <10 g/cm^2 are obtained over the full parameter range studied, with even higher accuracy for inclined incoming directions. In addition, by applying the developed method to dense arrays of radio antennas, the energy threshold for the radio detection of extensive air showers can be significantly lowered. The proposed method can be incorporated in operational and future cosmic particle observatories and with its high accuracy it has the potential to play a crucial role in unravelling the composition of the ultra-high-energy cosmic-particle flux.

СТВОРЕННЯ ТА АПРОБАЦІЯ НИЗЬКОЧАСТОТНОЇ РАДІОАСТРОНОМІЧНОЇ АНТЕНИ ДЛЯ ДОСЛІДЖЕНЬ ОБ'ЄКТІВ ВСЕСВІТУ ЗІ ЗВОРОТНОГО БОКУ МІСЯЦЯ

Purpose: Theoretical and experimental studies of the active antenna – an element of the low-frequency radio telescope antenna array for the future observatory on the farside of the Moon. Design/methodology/approach: To study the active antenna, consisting of a complex-shaped dipole and a low-noise amplifier, we used its mathematical model in the form of a two-port network, whose electrical parameters are set by the scattering matrix, the noise parameters being set by the covariance matrix of the spectral densities of noise waves. This model allows ma[1]king the correct analysis of the signal-to-noise ratio at the active antenna output with account for the external and internal noise sources. The modelling results were compared with those of experimental measurements of antenna characteristics. A series of radio astronomy observations were made with the developed antenna under the Earth environmental conditions. Findings: A numerical analysis of the radio telescope active antenna parameters has been made in a wide frequency range of 4–40 MHz. Two versions of the low-noise amplifier were developed to operate in the active antenna under the space and Earth environmental conditions. Under the Earth conditions, it has been experimentally proven that the range of problems, which such radio telescopes can effectively solve at low frequencies, is quite wide – from the solar research to the search for cosmological effects. Conclusions: The results of numerical simulations and experimental measurements obtained in this work have shown a satisfactory agreement between them for the most of the frequency range. The results of this work can be useful in the research and development of active antennas designed for operation at the decameter and hectometer wavelength ranges, particularly those intended for using under the space environmental conditions. Keywords: active antenna, Moon, radio astronomy observations, sensitivity

Expected performance of air-shower measurements with the radio-interferometric technique

Interferometric measurements with arrays of radio antennas are a powerful and widely used technique in astronomy. Recently, this technique has been revisited for the reconstruction of extensive air showers []. This “radio-interferometric technique” exploits the coherence in the radio emission emitted by billions of secondary shower particles to reconstruct the shower parameters, in particular the shower axis and depth of the shower maximum X max. The accuracy previously demonstrated on simulations with an idealized detector is very promising. The prospect of an accurate X max measurement for inclined air showers combined with measurements of the electromagnetic energy (also with radio antennas) and the muonic shower content (via ground particle detectors) is very intriguing as it would provide a high sensitivity to the mass of cosmic rays, key information to study their origin. In this article we evaluate the potential of interferometric X max measurements using (simulated) inclined air showers with sparse antenna arrays under realistic conditions. To determine prerequisites for the application of the radio-interferometric technique with various antenna arrays, the influence of inaccuracies in the time synchronisation between antennas and its inter-dependency with the antenna density is investigated in detail. We find a strong correlation between the antenna multiplicity (per event) and the maximum acceptable time jitter, i.e., inaccuracy in the time synchronisation. For data recorded with a time synchronisation accurate to within 1 ns in the commonly used frequency band of 30 MHz to 80 MHz, an antenna multiplicity of >50 is needed to achieve an X max resolution of g cm−2. For data recorded with 2 ns accuracy, already ≳ 200 antennas are needed to achieve this X max resolution. Furthermore, we find no advantage reconstructing X max from data simulated at higher observation frequencies, i.e., up to several hundred MHz. Finally, we provide a generalisation of our results from very inclined air showers to vertical geometries.

Estimating the carbon footprint of the GRAND project, a multi-decade astrophysics experiment

We present a pioneering estimate of the global yearly greenhouse gas emissions of a large-scale Astrophysics experiment over several decades: the Giant Array for Neutrino Detection (GRAND). The project aims at detecting ultra-high energy neutrinos with a 200,000 radio antenna array over 200,000 km2 as of the 2030s. With a fully transparent methodology based on open source data, we calculate the emissions related to three unavoidable sources: travel, digital technologies and hardware equipment. We find that these emission sources have a different impact depending on the stages of the experiment. Digital technologies and travel prevail for the small-scale prototyping phase (GRANDProto300), whereas hardware equipment (material production and transportation) and data transfer/storage largely outweigh the other emission sources in the large-scale phase (GRAND200k). In the mid-scale phase (GRAND10k), the three sources contribute equally. This study highlights the considerable carbon footprint of a large-scale astrophysics experiment, but also shows that there is room for improvement. We discuss various lines of actions that could be implemented. The GRAND project being still in its prototyping stage, our results provide guidance to the future collaborative practices and instrumental design in order to reduce its carbon footprint.

The Prototype Incoherent Scatter Radar System of Nanchang University

The incoherent scattering radar (ISR) is the only ground device on Earth that can detect the parameters of the ionospheric plasma because of its large detection range, high detection accuracy, and high spatial resolution. The prototype ISR system of Nanchang University has been completed now. Compared to the existing ISR systems in the world, which have a high radio frequency (RF) power and antenna array, high power consumption, expensive equipment operation, and maintenance costs, the radar has the advantages of low power consumption, low cost, and modularity. This radar system uses novel techniques of software-defined radio (SDR) and active phased array antennas to detect changes in the ionosphere. This article introduces the system design and antenna array of the software-defined radar prototype. The built-in radar transmitting and receiving equipment and specific radar parameters are described in detail and the radar detection results under different detection conditions are presented.

A proposed optical frequency synchronization system for the South African MeerKAT radio telescope

Abstract The South African MeerKAT radio telescope, a precursor to the Square Kilometre Array (SKA) will be incorporated into the mid-frequency component of SKA Phase 1. After a decade of planning, designing and construction, the MeerKAT radio antenna was officially inaugurated in July of 2018. Several exciting astronomical phenomena have already been observed with the MeerKAT radio telescope. Images produced from radio waves collected by the telescope revealed a wealth of ground-breaking astronomical wonders. For radio antenna array applications, the image quality is associated to the accuracy and stability of the phase measurements. The MeerKAT radio instrument is no exception to this, as ultra-stable clock signals will be disseminated to remote dishes across optical fibre up to 12 km in length. In this paper, with the purpose of application to MeerKAT, we propose and demonstrate a novel frequency dissemination and synchronisation system using a vertical cavity surface emitting laser (VCSEL) based phase correction actuator together with the inherent chromatic dispersion properties of the fibre. Frequency dissemination stabilities of 4.44 × 10−12 at 1 s and 4.86 × 10−14 at 104 s were successfully measured across the 26 km G.655 fibre link.

GRAND: A Giant Radio Array for Neutrino Detection

GRAND will be a distributed set of about 20 arrays of radio antennas, totalling 200,000 km^22. We aim to study the ultra high energy universe through the detection of neutrinos, photons and cosmic rays at energies at the EeV scale. In addition GRAND will be used to study astronomical objects like FRBs and GRBs. We will describe the physics motivation, the detection strategy, the first stages of GRAND and the path to creating the complete setup.

Detector developments for a hybrid particle and radio array for cosmic-ray air-shower detection

Large-scale air-shower arrays could profit from a radio sub-detector as the radio emission in air showers is sensitive to the electromagnetic component. In particular, with an array of radio antennas in combination with particle detectors highly inclined EAS can be detected. This gives rise to new science cases, e.g. the search for PeV gamma rays coming from the Galactic Center at the South Pole, from where it is visible all over the year at an inclination of 61° degree. We report on progress and plans in the development of an optimized hybrid detector.

Air Shower Detection by Arrays of Radio Antennas

Antenna arrays are beginning to make important contributions to high energy astroparticle physics supported by recent progress in the radio technique for air showers. This article provides an update to my more extensive review published in Prog. Part. Nucl. Phys. 93 (2017) 1. It focuses on current and planned radio arrays for atmospheric particle cascades, and briefly references to a number of evolving prototype experiments in other media, such as ice. While becoming a standard technique for cosmic-ray nuclei today, in future radio detection may drive the field for all type of primary messengers at PeV and EeV energies, including photons and neutrinos. In cosmic-ray physics accuracy becomes increasingly important in addition to high statistics. Various antenna arrays have demonstrated that they can compete in accuracy for the arrival direction, energy and position of the shower maximum with traditional techniques. The combination of antennas and particles detectors in one array is a straightforward way to push the total accuracy for high-energy cosmic rays for low additional cost. In particular the combination of radio and muon detectors will not only enhance the accuracy for the cosmic-ray mass composition, but also increase the gamma-hadron separation and facilitate the search for PeV and EeV photons. Finally, the radio technique can be scaled to large areas providing the huge apertures needed for ultra-high-energy neutrino astronomy.

A Surface Radio Array for the Enhancement of IceTop and its Science Prospects

Radio detection of air showers in the current era has progressed immensely to effectively extract the properties of these air showers. Primary cosmic rays with energies of hundreds of PeV have been successfully measured with the method of radio detection. There are also attempts to observe high-energy neutrinos with this technique. Current radio experiments measuring cosmic-ray air showers mostly operate in the frequency range of 30-80 MHz. An optimization of the frequency band of operation can be done for maximizing the signal-to-noise ratio that can be achieved by an array of radio antennas at the South Pole, operated along with IceTop. Such an array can improve the reconstruction of air showers performed with IceTop. The prospect of using such an optimized radio array for measuring gamma rays of PeV energies from the Galactic Center is discussed.

Physics Potential of a Radio Surface Array at the South Pole

A surface array of radio antennas will enhance the performance of the IceTop array and enable new, complementary science goals. First, the accuracy for cosmic-ray air showers will be increased since the radio array provides a calorimetric measurement of the electromagnetic component and is sensitive to the position of the shower maximum. This enhanced accuracy can be used to better measure the mass composition, to search for possible mass-dependent anisotropies in the arrival directions of cosmic rays, and for more thorough tests of hadronic interaction models. Second, the sensitivity of the radio array to inclined showers will increase the sky coverage for cosmic-ray measurements. Third, the radio array can be used to search for PeV photons from the Galactic Center. Since IceTop is planned to be enhanced by a scintillator array in the near future, a radio extension sharing the same infrastructure can be installed with minimal additional effort and excellent scientific prospects. The combination of ice-Cherenkov, scintillation, and radio detectors at IceCube will provide unprecedented accuracy for the study of highenergy Galactic cosmic rays.

A Scintillator and Radio Enhancement of the IceCube Surface Detector Array

An upgrade of the present IceCube surface array (IceTop) with scintillation detectors and possibly radio antennas is foreseen. The enhanced array will calibrate the impact of snow accumulation on the reconstruction of cosmic-ray showers detected by IceTop as well as improve the veto capabilities of the surface array. In addition, such a hybrid surface array of radio antennas, scintillators and Cherenkov tanks will enable a number of complementary science targets for IceCube such as enhanced accuracy to mass composition of cosmic rays, search for PeV photons from the Galactic Center, or more thorough tests of the hadronic interaction models. Two prototype stations with 7 scintillation detectors each have been already deployed at the South Pole in January 2018. These R&amp;D studies provide a window of opportunity to integrate radio antennas with minimal effort.

Latest results on the analysis of the radio frequency spectrum emitted by high energy air showers with LOFAR

The LOw Frequency ARay (LOFAR) is a multi-purpose radio antenna array aimed to detect radio signals in the frequency range 10 - 240 MHz, covering a largesurface in Northern Europe with a higher density in the Netherlands. Analytical calculations and simulation studies performed in the 2000s indicate a dependence of the radio frequency spectrum on cosmic-ray characteristics. The high number density of radio antennas at the LOFAR core allows to characterise the observed cascade in a detailed way. The radio signal emitted by air showers in the atmosphere has been studied accurately in the 30 - 80 MHz frequency range. The analysis has been conducted on simulated eventsand on real data detected by LOFAR since 2011. The final aim of this study is to find an independent method to infer information of primary cosmic rays for improving the reconstruction of primary particle parameters. Results show a strong dependence of the frequency spectrum on the distance to the shower axis for both real data and simulations. Furthermore, results show that this method is very sensitive to the precision in reconstructing the position of the shower axis at ground, and to different antenna calibration procedures. A correlation between the frequency spectrum and geometrical distance to the shower maximum development Xmax has also been investigated.

Measurements of Horizontal Air Showers with the Auger Engineering Radio Array

The Pierre Auger Observatory is the largest observatory for the detection of cosmic rays. With the Auger Engineering Radio Array (AERA) we measure the emitted radio signal of extensive air showers and reconstruct properties of the primary cosmic rays. For horizontal air showers (zenith angles larger than 60°) the signal is distributed over a large area of more than several km2. Therefore, detection of air showers using a sparse radio antenna array, compatible with the 1500 m distance between the 1600 surface detector stations, is possible. The radio technique is sensitive to the electromagnetic component of air showers. Combining radio detection with particle information from the surface detector of the Observatory, which at large zenith angles mostly detects muons, allows to study the cosmic ray composition for horizontal air showers.