Radio Interferometer System Research Articles

A Method for Positioning and Timing Support of Remote Users based on Mobile Radio Interferometry

The results of a comparative analysis of methods for positioning and timing support of remote users based on GNSS measurements from a GLONASS receiver and observational data on quasar radiation from compact very long base radio interferometric (VLBI) systems are discussed. Using radio telescope measurements increases the stability of positioning-and-timing and navigation support of users owing to observations of radio-frequency radiation emitted by the sources of natural origin. The approach proposed in this paper focuses on using radio interferometry for precision positioning and timing of remote radio telescopes. This method can be helpful for specific applications relevant to positioning and timing support for remote users with an arbitrary positioning topology.

Sunyaev–Zel’dovich profile fitting with joint AMI-Planck analysis

ABSTRACT We develop a Bayesian method of analysing Sunyaev–Zel’dovich measurements of galaxy clusters obtained from the Arcminute Microkelvin Imager (AMI) radio interferometer system and from the Planck satellite, using a joint likelihood function for the data from both instruments. Our method is applicable to any combination of Planck data with interferometric data from one or more arrays. We apply the analysis to simulated clusters and find that when the cluster pressure profile is known a priori, the joint data set provides precise and accurate constraints on the cluster parameters, removing the need for external information to reduce the parameter degeneracy. When the pressure profile deviates from that assumed for the fit, the constraints become biased. Allowing the pressure profile shape parameters to vary in the analysis allows an unbiased recovery of the integrated cluster signal and produces constraints on some shape parameters, depending on the angular size of the cluster. When applied to real data from Planck-detected cluster PSZ2 G063.80+11.42, our method resolves the discrepancy between the AMI and Planck Y-estimates and usefully constrains the gas pressure profile shape parameters at intermediate and large radii.

Physical modelling of galaxy clusters detected by thePlancksatellite

We present a comparison of mass estimates for $54$ galaxy cluster candidates from the second Planck catalogue (PSZ2) of Sunyaev-Zel'dovich sources. We compare the mass values obtained with data taken from the Arcminute Microkelvin Imager (AMI) radio interferometer system and from the Planck satellite. The former of these uses a Bayesian analysis pipeline that parameterises a cluster in terms of its physical quantities, and models the dark matter & baryonic components of a cluster using NFW and GNFW profiles respectively. Our mass estimates derived from Planck data are obtained from the results of the Bayesian detection algorithm PowellSnakes (PwS), are based on the methodology detailed in the PSZ2 paper, and produce two sets of mass estimates; one estimate is calculated directly from the angular radius $\theta$ - integrated Comptonisation parameter $Y$ posterior distributions, and the other uses a `slicing function' to provide information on $\theta$ based on X-ray measurements and previous Planck mission samples. We find that for $37$ of the clusters, the AMI mass estimates are lower than both values obtained from Planck data. However the AMI and slicing function estimates are within one combined standard deviation of each other for $31$ clusters. We also generate cluster simulations based on the slicing-function mass estimates, and analyse them in the same way as we did the real AMI data. We find that inclusion in the simulations of radio-source confusion & CMB noise and measurable radio-sources causes AMI mass estimates to be systematically low.

Experimental determination of physical processes in space, leading to deviations of radio synchrotron radiation spectra from the power law

We present universal formulas for spectral characteristics of cosmic radio sources of synchrotron radiation upon the presence of spectral density maxima at certain frequencies (spectra with negative curvature) taking into account most typical physical processes observed in space. On the basis of long-term observations of angular radiation structure of cosmic radio sources in the decameter wavelength range by the URAN radio interferometer system, we determine most probable physical processes resulting in spectra with extremum values for several quasars, radio galaxies, and their separate components. On the basis of these data, we estimate some parameters of cosmic medium, magnetic field, and angular sizes of compact radio sources and their components.

Fundamental study on location of a partial discharge source with a VHF‐UHF radio interferometer system

AbstractThe electromagnetic waves emitted from partial discharges (PD) due to material defects in high‐voltage electric power apparatus and facilities are broadband signals including VHF, UHF (Very High Frequency, Ultra High Frequency). A new VHF‐UHF radio interferometer system (VURIS) for locating PD source has been designed, constructed, and tested. The system is based on the idea of using the Fourier transform to extract the phase differences of different frequency components between a pair of received signals and computing the direction of the electromagnetic waves emitted from the PD source. It can be small in size, because UHF half‐wavelength dipole antennas are used to receive the electromagnetic waves and the baseline between the antennas is short. It requires fewer antennas to achieve equivalent angular resolution than a narrow‐band interferometer system, which requires multiple baselines corresponding to a few times the half‐wavelength of the observation frequency. Therefore, its use reduces operating time at the measurement site because it is not necessary to arrange many antennas at many positions. The indoor test results indicate that the system is able to estimate the arrival angle of electromagnetic waves emitted from PD sources. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 144(1): 32–41, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10145

VHF-UHF帯電波干渉計システムによる部分放電源特定のための基礎研究

The electromagnetic waves emitted from partial discharge (PD) due to material defects in high-voltage electric power apparatus and facilities are broadband signals including VHF, UHF (Very High Frequency, Ultra High Frequency). A VHF-UHF radio interferometer system (VURIS) for locating PD source has been originally designed, constructed and tested. The system is based on the idea extracting the phase differences at different frequencies between a pair of the received signals by the Fourier transform and computing the direction of the electromagnetic waves emitted from PD source. It can be small-sized, more suitable for compact and portable system, because UHF half-wavelength dipole antennas are used to receive the electromagnetic waves and the baseline between the antennas is very short. And it requires fewer antennas to achieve equivalent angular resolution than a narrow band interferometer system, which requires multiple baselines corresponding to a few times of half-wavelength of the observation frequency. Therefore, it's able to reduce the operating time at the measurement site because it's not needed to arrange many antennas at the many points. The indoor test results indicate that the system is able to estimate the arrival angle of the electromagnetic waves emitted from PD source.

Observations of lightning phenomena using radio interferometry

A radio interferometer system is described which utilizes multiple baselines to determine the direction of lightning radiation sources with an angular resolution of a few degrees and with microsecond time resolution. An interactive graphics analysis procedure is used to remove fringe ambiguities from the data and to reveal the structure and development of lightning discharges inside the storm. Radiation source directions and electric field waveforms have been analyzed for different types of breakdown events for two lightning flashes. These include the initial breakdown and K type events of in‐cloud activity, the leaders of initial and subsequent strokes to ground, and activity during and following return strokes. Radiation during the initial breakdown of one flash was found to consist of intermittent, localized bursts of radiation that were slow moving. Source motion within a given burst was unresolved by the interferometer but was detected from burst to burst, with negative charge being transported in the direction of the breakdown progression. Radiation during initial leaders to ground was similar but more intense and continuous and had a characteristic intensity waveform. Radiation from in‐cloud K type events is essentially the same as for dart leaders; in both cases it is produced at the leading edge of a fast‐moving negative streamer that propagates along a well‐defined, often extensive, path. K type events are sometimes terminated by a fast field change that appears analogous to the field change of a return stroke. Dart leaders are sometimes observed to die out before reaching ground; these are termed “attempted leaders” and, except for their greater extent, are no different than K type events. Several modes of breakdown during and after return strokes have been documented and analyzed. One mode corresponds to the launching of a positive streamer away from the upper end of the leader channel, apparently as the return stroke reaches the leader start point. In another mode, the quenching of the dart leader radiation upon reaching ground reveals concurrent breakdown in the vicinity of the source region for the leader. In both instances the breakdown appears to establish channel extensions or branches that are followed by later activity of the flash. Finally, a new type of breakdown event has been identified whose electric field change and source development resemble those of an initial negative leader but which progresses horizontally through the storm. An example is shown which spawned a dart leader to ground.

Geopotential resonances on Vanguard orbits

Since their establishment in 1959 the orbits of Vanguard 3 (1959-7A) and the Vanguard 2 rocket (1959-2B) have been slowly contracting through at least five strong resonances of eleventh order. Tracking with Baker-Nunn cameras and the U.S. Navy space surveillance (radio interferometer) system over a 14-year period has revealed resonant fluctuations on them of up to 0.035 deg in inclination (peak to peak). Six geopotential terms (lumped coefficients) of eleventh order and three of twenty-second order have been measured by using orbit inclinations derived from this tracking record. The terms of eleventh order are significantly smaller than is predicted by Kaula's rule. (The lumped coefficients are sensitive to geopotential effects as high as thirty-seventh degree.) These observed terms are compatible with a recent 27-satellite geopotential solution (GEM 7) whose formal coefficent errors are increased by a factor of 3.3.

Radio Interferometer Phase-Channel Combiner Mod. II for the Navy Space Surveillance System

The Space Surveillance System developed at the U. S. Naval Research Laboratory, Washington, D. C., for the detection of earth satellites forms a fence across the southern part of the United States. Four receiving sites are alternated with three transmitting sites which illuminate satellites with radio energy as they traverse the fence. The angle of arrival of the reflected energy is measured at each receiving station by a compound radio interferometer. These signals yield a multiplicity of channels which are normally recorded on paper, read and resolved by using slide rules and/or mathematical tables. Operationally the resolution is done by a computer. With the increasing satellite population the number of fence crossings has increased considerably. Automation in the detection process is needed to facilitate identification and sorting of satellites from each other if a large backlog of data is to be avoided. The purpose of this report is to describe an electronic system which automatically combines several noisy ambiguous radio interferometer phase channels into one unambiguous quiet channel. This technique results in that given a multi-baseline radio interferometer system, normally having high angular resolution capability accompanied with the usual interferometer ambiguity problem associated with deciphering the multiple phase signal outputs it can be instrumented directly into a single unambiguous signal output which has an accuracy and resolution proportional to the longest baseline in the interferometer and whose noise content is inversely proportional to this baseline.

Calibration of Minitrack Mark II

view Abstract Citations (2) References (7) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Calibration of Minitrack Mark II Kahn, Werner D. Abstract . The Army Map Service is planning to use U.S. earth satellites for geodetic purposes. Minitrack Mark II, a radio interferometer system, designed and developed by the Naval Research Laboratory under the direction of R. L. Easton, will be used to track the satellites. This paper treats the calibration of Minitrack Mark II by an error analysis of preliminary results obtained by tracking stellar radio sources. The resulting data are then used in the determination of the coefficients of Mayer's equation for the purpose of determining instrumental errors in both azimuth and collima- tion. An example, using the Taurus and Cassiopeia sources, is given in which the mean square error in the recorded times of upper transit was found to correspond to positional uncertainty of +45'.'8. Publication: The Astronomical Journal Pub Date: December 1957 DOI: 10.1086/107561 Bibcode: 1957AJ.....62..396K full text sources ADS |