scholarly journals An Acousto-optical Image Processor and Its Application to a 160 MHz Interferometer

1979 ◽  
Vol 49 ◽  
pp. 165-172
Author(s):  
Keizo Kai ◽  
Takeo Kosugi
Keyword(s):  
Solar Radio ◽  
Signal To Noise Ratio ◽  
The Sun ◽  
Optical Processing ◽  
Signal To Noise ◽  
Simulation Experiments ◽  
Radio Observatory ◽  
Image Processor ◽  
Radio Emissions ◽  
Solar Observations

AbstractRadio emissions from the Sun are characterized by extremely rapid time variation. Although they are relatively strong, the signal to noise ratio becomes critical when we observe them with high resolution in space and time. To improve the S-N ratio, we have investigated the feasibility of an acousto-optical processing of interferometer images and applied it to the 160 MHz interferometer of the Nobeyama Solar Radio Observatory. We present here results of simulation experiments and preliminary solar observations with the new image processor.

High Resolution Solar Observations at Three Frequencies: 1424 MHz, 696 MHz and 408 MHz

1967 ◽  
Vol 1 (2) ◽  
pp. 45-46
Author(s):  
D. G. Cole ◽  
R. F. Mullaly ◽  
A. Watkinson
Keyword(s):  
High Resolution ◽  
Radio Emission ◽  
Solar Radio ◽  
Solar Radio Emission ◽  
The Sun ◽  
Physical Mechanisms ◽  
Solar Observations ◽  
Source Structure ◽  
East West

During the period 1966 July 12 to August 5 observations were made of the Sun at three radio observatories. The instruments used were the east-west arm of the Mills cross at Molonglo (408 MHz) and the Christiansen cross at Fleurs (696 MHz and 1424 MHz). The aim of these observations was to study the discrete sources of the slowly varying component of solar radio emission, while activity was comparatively quiet. The three frequencies enabled the variation of source structure with height of solar atmosphere to be studied. It has been pointed out by Swarup et al., and Christiansen et al. that the determination of the frequency dependence of these discrete sources is important for defining the physical mechanisms causing the radio emission.

scholarly journals Recent Development of the Nobeyama 17GHz Interferometer and Some Initial Results

1980 ◽  
Vol 86 ◽  
pp. 123-126
Author(s):  
Keizo Kai
Keyword(s):  
Spatial Resolution ◽  
Time Resolution ◽  
Solar Radio ◽  
High Time Resolution ◽  
The Sun ◽  
Radio Observatory ◽  
Time Calibration ◽  
Drift Scan ◽  
Time Variations ◽  
Initial Results

We have constructed a 17GHz interferometer of a multi-correlator type at the Nobeyama Solar Radio Observatory. Novel features of the new interferometer are summarized as (i) high time-resolution up to 0.8 s and (ii) “real-time” calibration of the whole system with an accuracy of ~ 2% for amplitudes and ~ 2° for phases. With the aid of these advantages over an interferometer of a conventional drift-scan type we are able to detect and follow rapid time variations of even a faint source (say, ~ 0.5 s.f.u.) on the Sun with a spatial resolution of ~ 40″. The interferometer has been put in operation since July 1978. We have recorded hundreds of bursts at 17GHz in a year including some tens of rapidly changing sources which would not precisely be measured so far. We present here some preliminary results of observations such as polarization structures of both rapidly changing and GRF bursts.

scholarly journals System Requirements for Polarization Capability

1984 ◽  
Vol 79 ◽  
pp. 569-573
Author(s):  
J. Tinbergen
Keyword(s):  
Signal To Noise Ratio ◽  
Point Sources ◽  
High Signal ◽  
The Sun ◽  
Proper Treatment ◽  
Signal To Noise ◽  
Observational Technique ◽  
Imaging Polarimetry ◽  
System Requirements ◽  
Optical Telescopes

The purpose of this paper is to point out that1) proper treatment of polarization by a telescope is not only important for polarimetry, but also for other observations requiring high signal-to-noise ratio, and2) this does put a constraint on telescope design, which, however, is not unduly restrictive.Polarimetry is the observational technique which can detect anisotropics in point sources, their environment, or the medium between them and us. Modern optical polarimetry can be linear or circular, and is making progress towards spectropolarimetry and imaging polarimetry using panoramic detectors (e.g. McLean, 1984). Given sufficient photons, the precision obtained is as high as 1 part in 50 000 (see Odell, 1981 for a project requiring this precision), but more often a precision between 1 part in 1 000 to 10 000 is sufficient. (Spectro)polarimetry has been applied to planets, the Sun and other stars, stellar systems and galaxy nuclei; for a few modern investigations, see Baur, 1981; Jones et al, 1981; Schmidt and Miller, 1980. Experience in radio-astronomy has shown that when facilities for polarimetry are offered, many applications emerge from the astronomical community, yielding data that cannot be obtained by other techniques. It is essential that at least some of the large optical telescopes are capable of ob-serving polarization cleanly.

OPTICAL PROCESSING WITH PHOTOREFRACTIVE COMPOUND SEMICONDUCTORS

1992 ◽  
Vol 01 (03) ◽  
pp. 609-638
Author(s):  
L.J. CHENG ◽  
D.T.H. LIU ◽  
K.L. LUKE
Keyword(s):  
Semiconductor Lasers ◽  
Signal To Noise Ratio ◽  
Compound Semiconductors ◽  
Experimental Results ◽  
Response Compatibility ◽  
Cross Polarization ◽  
Optical Processing ◽  
Signal To Noise ◽  
Material Response ◽  
Noise Ratio

Photorefractive compound semiconductors are attractive for optical processing because of fast material response, compatibility with semiconductor lasers, and availability of cross polarization diffraction for enhancing signal-to-noise ratio. This paper presents a collection of recent experimental results on optical processing using photorefractive GaAs and InP. The results demonstrate the feasibility of using photorefractive compound semiconductors as dynamic holographic interaction media for optical processing applications.

scholarly journals Consistent and accurate estimation of stellar parameters from HARPS-N Spectroscopy using Deep Learning

2021 ◽  
Vol 2 ◽  
Author(s):  
Frederik Boe Hüttel ◽  
Line Katrine Harder Clemmensen
Keyword(s):  
Signal To Noise Ratio ◽  
Rotational Velocity ◽  
High Accuracy ◽  
Data Driven ◽  
Accurate Estimation ◽  
The Sun ◽  
Signal To Noise ◽  
Wide Range ◽  
Processing Steps ◽  
Astrophysical Research

Consistent and accurate estimation of stellar parameters is of great importance for information retrieval in astrophysical research. The parameters span a wide range from effective temperature to rotational velocity. We propose to estimate the stellar parameters directly from spectral signals coming from the HARPS-N spectrograph pipeline before any spectrum-processing steps are applied to extract the 1D spectrum. We propose an attention-based model to estimate the stellar parameters, which estimate both mean and uncertainty of the stellar parameters through estimation of the parameters of a Gaussian distribution. The estimated distributions create a basis to generate data-driven Gaussian confidence intervals for the estimated stellar parameters. We show that residual networks and attention-based models can estimate the stellar parameters with high accuracy for low Signal-to-noise ratio (SNR) compared to previous methods. With an observation of the Sun from the HARPS-N spectrograph, we show that the models can estimate stellar parameters from real observational data.

Comparing different types of solar flares with radio bursts detected by SMOS

2020 ◽  
Author(s):  
Manuel Flores Soriano ◽  
Consuelo Cid
Keyword(s):  
Space Weather ◽  
Early Warning ◽  
Solar Flares ◽  
Solar Radio ◽  
The Sun ◽  
Radio Bursts ◽  
Radio Observatory ◽  
X Ray ◽  
Different Types ◽  
Mass Ejection

<p>SMOS is an Earth observing satellite that is been adapted to provide full polarization observations of the Sun at 1.4 GHz 24 hours a day. Its solar radio observations from the last decade will be released to the community by the middle of this year. In this presentation we show the capabilities of SMOS as a solar radio observatory and compare some of the most relevant radio bursts with data from GOES, LASCO, SDO and RSTN. We show how SMOS responds to different kinds of solar flares depending on their x-ray flux, and the kind of mass ejection or solar dimming that they have produced, if any. In addition to this we also show the potential of SMOS as a space weather tool to monitor GNSS satellites signal fades and to provide an early warning of Earth-directed coronal mass ejections.</p>

Geomagnetic Reference Map Denoising Based on Singular Entropy

2014 ◽  
Vol 543-547 ◽  
pp. 912-916
Author(s):  
Zhan Long Zhu ◽  
Gong Liu Yang ◽  
Yan Yong Wang ◽  
Yuan Yuan Liu
Keyword(s):  
Information Entropy ◽  
Signal To Noise Ratio ◽  
Singular Values ◽  
Signal To Noise ◽  
Simulation Experiments ◽  
Noise Disturbance ◽  
Asymptotic Characteristic ◽  
Reference Map ◽  
Simulation Results ◽  
Matching Probability

To weaken the noise disturbance of GRM and improve the matching precision and matching probability of inertial/geomagnetic system, this paper proposed a method for denoising based on SVD. Firstly, from the perspective of information entropy, the singular entropy is introduced and the inner link between singular entropy and signal-to-noise ratio (SNR) is analyzed. Secondly, the method based on the asymptotic characteristic of the probabilities associated with the different singular values order (SVO) is proposed. Lastly, by utilizing practical GRM, the denoising analysis about the proposed method is demonstrated and later simulation experiments of GMN are accomplished. Simulation results show that the method is feasible and reliable.

scholarly journals FSR Systems for Detection of Air Objects Using Cosmic Radio Emissions

Sensors ◽  
2021 ◽  
Vol 21 (2) ◽  
pp. 465
Author(s):  
Hristo Kabakchiev ◽  
Vera Behar ◽  
Ivan Garvanov ◽  
Dorina Kabakchieva ◽  
Avgust Kabakchiev ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Cosmic Radio ◽  
Joint Detection ◽  
Signal To Noise ◽  
Theoretical Possibility ◽  
Forward Scatter ◽  
Direct Signal ◽  
Radio Emissions ◽  
Detection Characteristics ◽  
Scattering Signal

The paper analyses the possibility of Forward Scatter Radar (FSR) systems to detect airplanes using cosmic emission from pulsars and planets (pulsar, Sun, Moon). A suboptimal multichannel algorithm for joint detection and evaluation of the parameters of the forward scattering signal created by an airplane (duration and velocity) is proposed, with preliminary compensation of the powerful direct signal emitted by cosmic sources (pulsar, Sun and Moon). The expressions for calculation of the Signal-to-Noise Ratio (SNR) at the input of the detector and the compensator are obtained. The detection characteristics are also obtained, and the requirements for the suppression coefficient of the compensator are evaluated. A methodology for calculating the maximum distance for detecting an aircraft using a described algorithm is proposed. The obtained results show that due to the Forward Scatter (FS) effect, there is the theoretical possibility to detect airplanes at close ranges by FSRs, which use very weak signals from cosmic sources.

Performance Analysis of WiMAX System Base on AMC Optimized Algorithm

2012 ◽  
Vol 532-533 ◽  
pp. 610-614
Author(s):  
Li Liu ◽  
Xiu Ping Zheng ◽  
Li Jun Li
Keyword(s):  
Performance Analysis ◽  
Channel Estimation ◽  
Performance Optimization ◽  
Signal To Noise Ratio ◽  
Ofdm System ◽  
Signal To Noise ◽  
Simulation Experiments ◽  
Coding Scheme ◽  
Slow Fading ◽  
Wimax System

Aimed at WiMAX-OFDM system, an optimized algorithm for AMC was proposed from the angle of channel estimation. Simulation experiments were carried on in SUI channels which were typically slow fading, and influences of the traditional AMC technology and optimized AMC algorithm on performance of system were analyzed. Results show that the optimized AMC algorithm not only improves accuracy of channel estimation, but also reduces errors between the predicted signal-to-noise ratio and the actual SNR, which makes selected modulation and coding scheme more reasonable. Finally, the WiMAX system can obtain performance optimization.

scholarly journals Temporal Behavior of Solar P-Modes from Gong and Golf Experiments

1998 ◽  
Vol 185 ◽  
pp. 227-228
Author(s):  
V.G. Gavryusev ◽  
E.A. Gavryuseva
Keyword(s):  
Time Series ◽  
Signal To Noise Ratio ◽  
Temporal Behavior ◽  
The Sun ◽  
Solar Oscillations ◽  
Signal To Noise ◽  
Data Set ◽  
Noise Ratio

We used the measurements of solar oscillations taken by GONG and GOLF experiments. The first set of data are the integrated images obtained from the complex GONG observations taken from June 10 of 1995 to January 7 of 1997, 578 days in total, referenced below as ts0 time series. Radial, dipole and quadrupole modes are well visible in this time series. The second data set is the GOLF time series obtained on-board SOHO mission from April 11, 1996 to June 22, 1997. GOLF observes the “Sun as a star”. This time series is similar to ts0 of GONG but of a better quality (better signal-to-noise ratio; uniform, practically uninterrupted data). Both experiments are significantly overlapped in time. Because of this the direct comparison between them is possible, and the effects visible in both observations support each other.

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