First Year Of Measurements Research Articles

Results of 11.6 GHz radiometric experiment in Kenya

Three experiments were set up within a joint African radiometric propagation measurement programme to provide data at frequencies above 10 GHz for predictive modelling. The results of the first year of measurements in Nairobi, Kenya, are reported. Significant differences are evident between the measured results and the CCIR rain zone and path attenuation predictions.

Results of 11.6 GHz radiometric experiment in Cameroon

Three experiments were set up within a joint African radiometric propagation measurement programme to provide data at frequencies above 10 GHz for predictive modelling. The results of the first year of measurements in Douala, Cameroon are reported. These show significant departures from the CCIR rain climate and path attenuation models.

Wind resource assessment in Sri Lanka

In the framework of the Sri Lanka-Netherlands Energy Programme an assessment of the wind and solar resources in the Central Highlands and Southern Lowlands of Sri Lanka was initiated in 1987. Actual data collection started end 1989. This paper reports the results of the first year of measurements. The results show a typical day-night wind pattern, with weak night-time winds and moderate to strong day-time winds peaking around 3 p.m. The pronounced sea breeze causes an augmentation and a directional change of the prevailing monsoonal winds. This is also reflected in the bimodal nature of the frequency distributions. The calculated outputs of a 250 kW wind turbine show promising values of the order of 800 to 900 kWh/m 2 per year. The monthly outputs peak in the period June–September, the period when the hydropower reservoirs in Sri Lanka are gradually emptying.

Polar stratospheric cloud observations over the Antarctic continent at Dumont d'Urville

The Istituto di Ricerca sulle Onde Electromagnetiche (IROE) two‐channel elastic backscattering lidar [Sacco et al., 1989], suitable for depolarization measurements, has been operated since January 8, 1989, at the French Antarctic base of Dumont d'Urville (66°40′S, 140°01′E). A continuous monitoring of the stratosphere was performed, which permitted measurement of the evolution of the background stratospheric aerosols and of polar stratospheric clouds (PSC) throughout the year. The data reported in this article correspond to the first year of measurements. Depolarization of the lidar signals was measured in order to obtain information on the type of clouds observed and on their particle size distribution. Both low (<10%) and high (>10%) depolarization ratios were detected, permitting discrimination between types Ia, Ib, and II PSC according to the classification given by Toon et al. (1990). Temporal continuity and high time resolution of the lidar measurements are evidence for altitude decreases in the PSC layers over periods of a few hours. These motions, if linked to sedimentation processes, led to values of velocity (≃10 cm s−1) compatible with large particles.

ATS-6 Millimeter Wave Propagation and Communications Experiments at 20 and 30 GHz

The Applications Technology Satellite (ATS-6) Millimeter Wave Experiment, developed and implemented by the NASA Goddard Space Flight Center, has provided the first direct measurements of 20-and 30-GHz Earth-space links from an orbiting satellite. Studies at eleven locations in the continental United States were directed at an evaluation of rain attenuation effects, scintillations, depolarization, site diversity, coherence bandwidth, and analog and digital communications techniques In addition to direct measurements on the 20-and 30-GHz links, methods of attenuation prediction with radars, rain gauges, and radiometers were developed and compared with the directly measured attenuation. This paper presents a review of the major results of the first year of measurements with ATS-6, with emphasis on the impact of the measurements on millimeter wave space systems design.