First measurement of scintillation and attenuation of 19.5 GHz beacon signal for experimental communication payload of ROCSAT-1

The ROCSAT-1 has been launched successfully on January 27, 1999. With employing transportable and fixed ground terminals to receive 19.5 GHz beacon signal of the experimental communication payload (ECP), the Ka band propagations experiment were carried out to study the atmospheric effects, including rain particles, clouds, water vapor content, melting hydrometeors, atmospheric refractivity fluctuations, and so on, on the satellite signal at Ka band over Taiwan area. Preliminary measurement shows that even during precipitation-free environment the variation range of 19.5 GHz beacon signal amplitude can be as large as 18 dB. Data analysis indicates that strong scintillations with peak-to-peak amplitude fluctuations greater than 5 dB are often observed under the cloudy condition. In addition, the frequency of amplitude fluctuation is higher at the low elevation angle than that at large elevation angle. A comparison between amplitude variation of beacon signal and sky noise temperature at 19.5 GHz measured by a ground-based radiometer is also made in this paper.