We present results of Very Long Baseline Array (VLBA) observations of PKS 0528+134 at five frequencies (2.3, 5.0, 8.4, 15.4, and 22.2 GHz). These quasi-simultaneous data enable us to study the spectral distribution of Very Long Baseline Interferometer (VLBI) components for the first time in this highly variable source, from which the central compact core is identified. Our observations indicate...

We present the results of six-epoch Very Long Baseline Array (VLBA) observations of 3C 66A. The high-resolution Very Long Baseline Interferometer (VLBI) maps obtained at multi-frequency (2.3, 8.4, and 22.2 GHz) simultaneously enabled us to identify the brightest compact component with the core. We find that the spectrum of the core can be reasonably fitted by the synchrotron self-absorption mod...

This paper examines options for orbit configurations a space interferometer. In contrast to previously presented concepts very long baseline interferometry, we propose combination of regular and retrograde near-Earth circular orbits in order achieve faster filling (u,v) coverage. With the rapid relative motion telescopes, it will be possible quickly obtain high quality images supermassive black...

The modernization of the GPS and the advent of the European Galileo will enhance the capability of quickly and correctly resolving the integer cycle carrier phase ambiguities in precise differential positioning. In this paper the performances of hybrid modernized GPS and Galileo positioning are analyzed for different scenarios by using the LAMBDA method in Japan. The scenarios include modernize...

Orbits for satellites o f the Global Positioning System (GPS) have been determined with submeter accuracy. Tests used to assess orbit accuracy include orbit comparisons from independent data sets, orbit prediction, ground baseline determination, and formal errors. One satellite tracked for 8 hours each day shows rms errors below I m even when predicted more than 3 days outside of a 1-week data ...

The ground-based optical interferometer with large apertures is a potential research tool for the study of stellar astrophysics and the synthesis of high-resolution stellar images. However, atmospheric turbulence can impose a significant limitation on the interferometer's performance. In order to reduce those degrading effects, we investigate the effectiveness of high-order adaptive optics in g...