Tropospheric delay statistics measured by two site test interferometers at Goldstone, California

Abstract

[1] Site test interferometers (STIs) have been deployed at two locations within the NASA Deep Space Network tracking complex in Goldstone, California. An STI measures the difference of atmospheric delay fluctuations over a distance comparable to the separations of microwave antennas that could be combined as phased arrays for communication and navigation. The purpose of the Goldstone STIs is to assess the suitability of Goldstone as an uplink array site and to statistically characterize atmosphere-induced phase delay fluctuations for application to future arrays. Each instrument consists of two~1 m diameter antennas and associated electronics separated by~200 m. The antennas continuously observe signals emitted by geostationary satellites and produce measurements of the phase difference between the received signals. The two locations at Goldstone are separated by 12.5 km and differ in elevation by 119 m. We find that their delay fluctuations are statistically similar but do not appear as shifted versions of each other, suggesting that the length scale for evolution of the turbulence pattern is shorter than the separation between instruments. We also find that the fluctuations are slightly weaker at the higher altitude site.

Measurements of phase fluctuations for reliable MIMO space communications

“…Based on the observation of these three days there is a strong suspicion that the sun and the rise of the phase fluctuations are correlated. Such a correlation is in accordance with the measured results in [5]. It has been evaluated that the system operates reliably for wind flow velocities up to 6 Beaufort (bft).…”

“…The averaging length is widely spread, e.g. from 10 samples per second [5], [6] up to one sample per 30 seconds [8]. As a consequence of this fact, the results are hardly comparable.…”

“…The measurement campaigns in [5]- [8] have in common that two or more antennas with different baselines focus on the same celestial source (satellite or cosmic compact radio source). The phase difference of the synchronously received signals of two antennas is then compared.…”

“…At present there are only a few measurement results available that allow prediction of the tropospheric influence on the phase of a radio signal. In the context of astronomical interferometry measurements some data has been published in [5]- [8].…”

Interferometric orbit determination for geostationary satellites

“…The signal-to-noise ratio presents a cyclic behavior where the negative lobes (daytime) are considerably noisier than the positive lobes (night time). Apart from the known atmospheric effects present during daytime [14], sun exposure of the cables connecting the two receivers might cause such behavior.…”