The space VLBI satellite HALCA was launched on February 12, 1997. It is the first Radio astronomy satellite. We report the performance of onboard radio astronomy system. Typical system noise ...temperatures are 70K and 90K at L and C band respectively. For K band, the apparent system noise temperature is 400 K. It is caused by the attenuation between the main antenna and the K band LNA. Bandpass characteristics of each observing band are almost the same as the ground test. The phase stability of local oscillators are around 5 degrees r.m.s. at C band. And the total gain of the receiving system and the bit distribution of high rate samplers are checked. Basically the in-orbit performance of the VLBI observing system matches the pre-launch ground test results.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Some problems owing to the magnetic field distribution often occur in magnetic powder flaw detection. For example, magnetic flux density concentrates locally because of geometry and configuration of ...magnetization equipment, and hence incorrect detection is caused. To overcome the problem two different techniques have been applied to a model of a square steel billet. The solution was obtained by using an AC nonlinear FEM analysis.
We have made VSOP observations of BL Lacertae (2200+420) using HALCA and the VLBA on 8 December 1997 at a resolution of 0.6 × 0.3 milliarcsec. The source structures are identified with the core and ...superluminal jet-components that are seen in VLBA images at 43 GHz from 1996 (Denn and Mutel 1998). Extended structure out to 20 milliarcsec from the core has been detected.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We investigate whether pc-scale jets of 3C 345 and 3C 279 are dominated by a normal plasma or an electron-positron plasma. We present a general condition that a jet component becomes optically thick ...for synchrotron self-absorption. The general condition gives a lower limit of the electron number density, with the aid of the surface brightness condition, which enables us to compute the magnetic field density. Comparing the lower limit with another independent constraint that is deduced from the kinetic luminosity, we can distinguish the matter content. We apply the procedure to the five components of 3C 345 (C2, C3, C4, C5, and C7) and the three components of 3C 279 (core, C3 and C4) of which angular diameters and radio fluxes at the peak frequencies were obtainable from literature. Evaluating the Doppler factors by their equipartition values, we find that four of the five components of 3C 345 and all the three components of 3C 279 are likely dominated by an electron-positron plasma.
We have investigated whether a pc-scale jet of 3C 279 is dominated by a normal plasma or an electron-positron plasma. By analyzing Very Long Baseline Interferometry data between 1983 and 1990, and ...utilizing the theory of synchrotron self-absorption, we have derived the lower limits for the proper electron number density. Comparing the lower limit with another independent constraint for the electron density that is deduced from the kinetic luminosity, we find that the core and components C3 and C4 are likely dominated by an electron-positron plasma.
We made a high-resolution VLBI observation of the gamma-ray loud quasar PKS 1622
$-$
297 with the HALCA spacecraft and ground radio telescopes at 5 GHz in 1998 February, almost 3 yr after the source ...exhibited a spectacular GeV gamma-ray flare. The source shows an elongated structure toward the west on the parsec scale. The visibility data are well modeled by three distinct components: a bright core and two weaker jet components. Comparison with previous observations confirms that the jet components have an apparent superluminal motion up to
$12.1 \,h^{-1} \, c$
, with the inner jet components having lower superluminal speeds. We applied the inverse Compton catastrophe model and derived a Doppler factor,
$\delta$
, of 2.45, which is rather lower than those of other gamma-ray loud active galactic nuclei (AGNs), suggesting that the source was in a more quiescent phase at the epoch of our observation. As an alternative probe of the subparsec-scale structure, we also present the results from multiepoch ATCA total flux monitoring, which indicate the presence of persistent intraday variability consistent with refractive interstellar scintillation. We examined the gamma-ray emission mechanism in light of these observations.
Three novel calculation methods for voltage-source problems with conductors, considering current distributions in conductors, have been developed using the finite element method and the A- phi ...formulation. The first is a dividing method for conductors. Equations for circuits including divided conductors are solved with Maxwell's equations. The second performs two sequential procedures: (1) current distributions are solved by putting electrical potentials on boundaries of conductors using Poisson's equation: and (2) eddy currents are solved by Maxwell's equations with the solutions of (1). The sum of both currents is the real distributions in conductors. The third is a direct method to put electric potentials as the scalar potential on the boundaries. These methods are applied to two models. The inductances were also measured, and the experimental results have shown good agreement with the calculations.< >
Abstract
The radio astronomy satellite HALCA was launched by the Institute of Space and Astronautical Science in 1997 February to participate in Very Long Baseline Interferometry (VLBI) observations ...with arrays of ground radio telescopes. HALCA is the main element of the VLBI Space Observatory Programme (VSOP), a complex international endeavor involving over 25 ground radio telescopes, five tracking stations and three correlators. Simultaneous observations with HALCA's 8 meter diameter radio telescope and ground radio telescopes synthesize a radio telescope over twice the size of the Earth, enabling the highest resolution 1.6 GHz and 5 GHz images to be made.
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