Tropospheric limitations of the measurement accuracy on coordinates of cosmic radio source

1976 ◽  
Vol 19 (11) ◽  
pp. 1167-1169
Author(s):  
A. A. Stotskii
Keyword(s):  
Radio Source ◽  
Measurement Accuracy ◽  
Cosmic Radio ◽  
Cosmic Radio Source

Ray paths from a cosmic radio source to a satellite in orbit

1961 ◽  
Vol 261 (1306) ◽  
pp. 423-434 ◽  
Keyword(s):  
Point Source ◽  
Radio Source ◽  
Numerical Calculations ◽  
Cosmic Radio ◽  
Strong Signal ◽  
Cosmic Radio Source ◽  
Ray Paths

A receiver mounted on a satellite in orbit above the maximum of the F 2 layer can receive radiation of frequencies that are totally reflected by the ionosphere. Two effects of reflexion in the upper part of the ionosphere are discussed in this paper; both occur particularly when the satellite enters or leaves a region in which it can receive radiation from a point source. The first of these effects is focusing, which will give a very strong signal at these points, and the second is interference between the two possible rays from the point source to the satellite. The theory of these two effects is discussed and some numerical calculations are described which demonstrate them for a particular model ionosphere.

scholarly journals The Angular Size of the Variable Radio Source Hydra?A

1955 ◽  
Vol 8 (4) ◽  
pp. 564 ◽  
Author(s):  
AWL Carter
Keyword(s):  
Radio Source ◽  
Angular Size ◽  
Cosmic Radio ◽  
The Sun ◽  
Cosmic Radio Source ◽  
Variable Radio ◽  
Variable Radio Source

Slee (1955) has shown that the discrete cosmic radio source Hydra-A shows variations in intensity at metre wavelengths. This is the first variable radio source to be found, other than the Sun, although Ryle and Elsmore (1951) investigated about one hundred northerly sources and found no significant variations in their intensities over a period of 18 months. The observations to be described here were undertaken firstly to check the variability of the source, then suspected by Slee, and secondly to measure its angular size and see whether this might also be variable.

The closest cosmic radio source

Nature ◽  
1980 ◽  
Vol 283 (5749) ◽  
pp. 718-719
Author(s):  
Alan Johnstone
Keyword(s):  
Radio Source ◽  
Cosmic Radio ◽  
Cosmic Radio Source

scholarly journals Interferometric observation of Cygnus-А discrete radiosource scintillations at Irkutsk Incoherent Scatter radar

2016 ◽  
Vol 2 (1) ◽  
pp. 34-43
Author(s):  
Мария Глоба ◽  
Mariia Globa ◽  
Роман Васильев ◽  
Roman Vasilyev ◽  
Дмитрий Кушнарев ◽  
...  
Keyword(s):  
Radio Source ◽  
Angular Size ◽  
Brightness Distribution ◽  
Statistical Characteristics ◽  
Cosmic Radio ◽  
Incoherent Scatter Radar ◽  
Incoherent Scatter ◽  
Cygnus A ◽  
Scatter Radar ◽  
Interferometric Observation

We propose a new method for analyzing data from the Irkutsk Incoherent Scatter Radar. The method allows us to accomplish interferometric observation of discrete cosmic radio source characteristics. In this study, we analyze ionospheric scintillations of the radio source Cygnus-A. Observations were made in 2013 during regular radar sessions within 5–15 days for different seasons; the effective time of observation was 15–30 minutes per day. For interferometric analysis, the properties of correlation (coherence) coefficient of two independent recording channels were used. The statistical analysis of data from the independent channels allows us to construct two-dimensional histograms of radio source brightness distribution with a period of 18 s and to determine parameters (the maximum position and the histogram width) representing position and angular size of the radio source for each histogram. It is shown that the change of statistical characteristics does not correlate with fluctuations in power (scintillations) of the signal induced by radio wave propagation through ionospheric irregularities.

scholarly journals ANALYSIS OF THE MAGNETIC STORMS CATALOG FOR MONITORING RADIO SOURCE FLUXE DATA WITH THE URAN-4 RADIO TELESCOPE IN THE ODESA MAGNETIC ANOMALY ZONE

2020 ◽  
Vol 25 (4) ◽  
pp. 324-330
Author(s):  
L. I. Sobitnyak ◽  
◽  
M. I. Ryabov ◽  
M. I. Orlyuk ◽  
A. L. Sukharev ◽  
...  
Keyword(s):  
Radio Source ◽  
Magnetic Storm ◽  
Magnetic Anomaly ◽  
Radio Telescope ◽  
Magnetic Storms ◽  
Radio Sources ◽  
Cosmic Radio ◽  
Geomagnetic Observatory ◽  
National Academy Of Sciences ◽  
Geomagnetic Disturbances

Purpose: Compilation of a digital catalog of magnetic storms in the Odesa magnetic anomaly zone in order to find the reasons for possible changes in the radiation fluxes of cosmic radio sources, according to observations at the URAN-4 radio telescope. Design/methodology/approach: Since 1987 until now, the radio flux of powerful galactic and extragalactic radio sources has been monitored at the URAN-4 radio telescope of the Odesa Observatory of the Institute of Radio Astronomy of the National Academy of Sciences of Ukraine. The monitoring program includes radio galaxies 3C274, 3C405 and supernova remnants 3C144, 3C461. Changes in the radio source flux level are determined by the ionosphere state due to the changes in space weather. At the “Odesa” geomagnetic observatory of the Institute of Geophysics of the National Academy of Sciences of Ukraine, the geomagnetic field measurements have been made since 1948. Simultaneously, the measurements of three elements of the geomagnetic field: horizontal component (H), vertical component (Z) and inclination (D), have been recorded. Findings: Using the “Odesa” geomagnetic observatory data, the digital catalog of magnetic storms was compiled for the measuring period of the powerful space radio source fluxes obtained with the URAN-4 radio telescope. For the magnetic storms monitored during the periods of 1987–1995 and 2000–2009, the date and time are shown for the beginning and the end of the magnetic storm, the magnetic storm duration, the amplitude of the three magnetic field elements, being H, Z, and D, and the magnetic storm type characteristic.The “Odesa” geomagnetic observatory is located near the magnetic anomaly zone. To find the distinctions in manifestations of the geomagnetic activity arisen owing to the magnetic anomaly existence, the geomagnetic disturbances recorded at the “Odesa” and “Moscow” (IZMIRAN, Russia) observatories were compared. It was shown that the total annual duration of the magnetic storms was longer in Odesa than in Moscow. This demonstrates some special role of the magnetic anomaly in the development of geomagnetic disturbances. Conclusions: The digital catalog of magnetic storms in the Odesa magnetic anomaly zone was compiled for the 1987–1995 and 2000–2009 periods. It is also planned to terminate working over the complete catalog of magnetic storms recorded at the “Odesa” observatory for the entire continuous period of monitoring space radio sources at the URAN-4 radio telescope in order to find the manifestations of geomagnetic disturbances impact upon the ionosphere state and changes of intensity in cosmic radio source fluxes. These studies are supplemented by the comparative analysis of the “Odesa” observatory geomagnetic data and the data from some other geomagnetic observatories. Key words: solar activity; monitoring variability of radio sources; magnetic storms; catalog of magnetic storms; magnetic anomaly

Methods for Restricting Maximum Exposure Rate in Computerized Adaptative Testing

Methodology ◽  
2007 ◽  
Vol 3 (1) ◽  
pp. 14-23 ◽  
Author(s):  
Juan Ramon Barrada ◽  
Julio Olea ◽  
Vicente Ponsoda
Keyword(s):  
Measurement Accuracy ◽  
Computerized Adaptive Testing ◽  
Computation Time ◽  
Adaptive Testing ◽  
Exposure Rate ◽  
Control Parameters ◽  
The Impact ◽  
Two Alternatives ◽  
Selection Of ◽  
Maximum Exposure

Abstract. The Sympson-Hetter (1985) method provides a means of controlling maximum exposure rate of items in Computerized Adaptive Testing. Through a series of simulations, control parameters are set that mark the probability of administration of an item on being selected. This method presents two main problems: it requires a long computation time for calculating the parameters and the maximum exposure rate is slightly above the fixed limit. Van der Linden (2003) presented two alternatives which appear to solve both of the problems. The impact of these methods in the measurement accuracy has not been tested yet. We show how these methods over-restrict the exposure of some highly discriminating items and, thus, the accuracy is decreased. It also shown that, when the desired maximum exposure rate is near the minimum possible value, these methods offer an empirical maximum exposure rate clearly above the goal. A new method, based on the initial estimation of the probability of administration and the probability of selection of the items with the restricted method ( Revuelta & Ponsoda, 1998 ), is presented in this paper. It can be used with the Sympson-Hetter method and with the two van der Linden's methods. This option, when used with Sympson-Hetter, speeds the convergence of the control parameters without decreasing the accuracy.

Structured methods for improving flow measurement accuracy in pipelines

2020 ◽  
pp. 30-35
Author(s):  
Gurami N. Akhobadze
Keyword(s):  
Flow Measurement ◽  
Measurement Accuracy ◽  
Directional Coupler ◽  
Signal To Noise Ratio ◽  
Scattered Wave ◽  
Orthogonal Polarization ◽  
Flow Sensors ◽  
Information Signal ◽  
Mass Flows ◽  
Processing Device

In the age of digital transformation of production processes in industry and science the development and design of intelligent flow sensors for granular and liquid substances transferring through pipelines becomes more important. With this in view new approaches for improving the accuracy of microwave flowmeters are proposed. Taking into account the characteristics ofelectromagnetic waves propagating through a pipeline, a wave scattered by inhomogeneities of the controlled medium is analyzed. Features of the transformation of the polarized scattered wave limiting the geometric dimensions of the pipeline and optimizing the values of the useful scattered signal are revealed. Expediency of collection of the information signal with orthogonal polarization of the scattered wave and through a directional coupler is substantiated. The method of estimating the measurement accuracy with reference to the signal-to-noise ratio at the input of the processing device is given. The research results can be used in cryogenic machine engineering to measure volume and mass flows of liquid cryogenic products.

Sign in / Sign up

Export Citation Format

Share Document