Satellite Information Systems Research Articles

Circular Waveguide Polarizer for Weather Radars and Satellite Information Systems

This research presents the design and main electromagnetic characteristics of the novel compact microwave waveguide polarizer. The developed device's structure is based on a circular waveguide and anti-phase conducting posts located in it. The application of a circular waveguide instead of a square one allowed simple integration of a polarizer with corrugated horn antennas. The obtaining of required phase difference using a posts-based design provides the possibility of fine tuning of the developed circular waveguide polarizer after its manufacturing process. In addition, simultaneous adaptive operation at orthogonal circular and linear polarizations is available in the antenna system including a polarizer with posts. An automatic control of posts height must be applied in a waveguide in order to provide this option. Numerical simulation, optimization, manufacture and measurements of the polarizer's characteristics were carried out in the operating band 7.4-8.5 GHz. Measured characteristics proved that the suggested circular waveguide polarizer provides good matching and polarization performance. Developed circular waveguide polarizer can be integrated in corrugated horn antenna systems and applied in modern weather radars and satellite information systems.

ВИСОКОЕФЕКТИВНИЙ ХВИЛЕВОДНИЙ ПОЛЯРИЗАТОР ДЛЯ СУПУТНИКОВИХ ІНФОРМАЦІЙНИХ СИСТЕМ

У сучасних супутникових інформаційних системах та безпровідних системах передачі даних широко використовують сигнали із коловими поляризаціями. Сигнали цього типу вимагають застосування спеціальних антенних систем із поляризаційним обробленням. Такий підхід дає можливість удвічі зекономити частотні ресурси, які є обмеженими. У результаті збільшується інформаційна ємність каналів передачі інформації в супутникових та інших інформаційних системах. Базовим елементом антенних систем із коловими поляризаціями є поляризатор. Такий пристрій здійснює перетворення електромагнітних хвиль із круговою поляризацією в лінійно поляризовані хвилі або навпаки. Використання поляризатора та ортомодового перетворювача в антенних системах забезпечує перетворення поляризації сигналів із одночасною передачею їх до розв’язаних хвилеводних каналів. Стаття містить результати аналізу та оптимізації нового високоефективного хвилеводного поляризатора для супутникових інформаційних систем. Конструкція розробленого поляризатора складається із хвилеводу квадратного перерізу з чотирма діафрагмами. Виконано оптимізацію поляризатора для його застосування в робочому діапазоні частот від 10,7 ГГц до 12,8 ГГц. Проаналізовано й оптимізовано фазові, поляризаційні характеристики та характеристики узгодження із застосуванням чисельного методу скінченного інтегрування. Розроблений хвилеводний поляризатор із чотирма діафрагмами забезпечує диференційний фазовий зсув 90° ± 3,5°, коефіцієнт стійної хвилі з напругою, меншою 1,24, коефіцієнт еліптичності, менший 0,53 дБ, кросполяризаційну розв’язку, вищу 30,3 дБ. Таким чином, створений новий поляризатор на основі квадратного хвилеводу з чотирма діафрагмами забезпечує якісну роботу в усьому робочому Ku-діапазоні частот 10,7–12,8 ГГц. Пристрій може широко використовуватися в сучасних антенних системах із поляризаційним обробленням сигналів у телекомунікаційних, радіолокаційних і супутникових інформаційних системах.

The models of transionospheric transmission channels with amplitude fading of signals

Descriptions of statistical models of narrow-band transionospheric radio lines with amplitude fading of signals due to the influence of the earth’s ionosphere are given. The models are based on the analytical description of signal propagation in randomly inhomogeneous media that generate temporal variations in signal amplitudes due to their reflection and scattering on ionospheric inhomogeneities. These analytical descriptions represent Rytov’s approximate solutions for the wave equation without taking into account the anisotropy due to the influence of the Earth’s magnetic field. The stationarity of the radio line associated with the temporal and spatial statistical characteristics of random temporal and spatial fluctuations of the electron density of ionospheric irregularities is considered as a parameter of the models that is important for applications. By calculating the considered models of radio lines with the parameters of the standard mid-latitude ionosphere, estimates of the temporal stationarity of radio lines for a number of velocities of movement of ionospheric irregularities are obtained. The calculated estimated values of the temporal stationarity of the considered radio lines due to the influence of the ionosphere are useful in the development of satellite information systems, in the selection of optimal signal structures and in the development of procedures for their processing during reception and synchronization.

ОРГАНИЗАЦИЯ КОМПЛЕКСНЫХ СИСТЕМ ОБЕСПЕЧЕНИЯ ЭКСПЛУАТАЦИОННОЙ НАДЕЖНОСТИ ПОДВИЖНОГО СОСТАВА

The use of digital and satellite information systems for the increase of quality and prompt maintenance and repair of rolling stock allows solving important transport tasks. On the modern stage the transportation process sets high requirements to operation of rolling stock that should be regulated by state standards. Modern machinery and technology should promote implementation of high-quality production in order to extend the life cycle of any product that responds the realization of production process. The international practice of standard application convincingly proves it. The paper proposes an organization of complex systems aimed at provision of operational reliability of rolling stock. The authors have determined possible reasons of non-compliance of the standards. As a result, they have set tasks on carrying out modern monitoring and execution of maintenance and repair.

Баллистические проблемы синтеза орбитального сегмента спутниковых систем информационного обеспечения на основе малых и сверхмалых космических аппаратов

Баллистические проблемы синтеза орбитального сегмента спутниковых систем информационного обеспечения на основе малых и сверхмалых космических аппаратов

On the concept of normative evaluation of cost-effectiveness of GLONASS application in coastal regions

Russia promotes the application of GLONASS satellite information system in regional economies. In three regions, the system has already been introduced and is widely used, 21 more regions are introducing the system. Experts believe that this process will take from 3 to 5 years. The introduction and integrated use of GLONASS pose a number of organisational and economic problems for regional administrations. One of such problems is the evaluation of economic benefit from GLONASS implementation in the region. Economics has developed a large number of methodological approaches to the calculation of such effects in different fields of satellite information application: Earth's remote probing, crop yield forecasts, forestry, water industry and agricultural monitoring, etc. However, the research shows that attempts to perform a calculation for various fields of satellite information application at a regional level prove the existing approaches to be inefficient due to the difficulties in obtaining initial data. To this effect, the authors developed a normative methodical approach to the calculation of the effect of integrated GLONASS application. This approach is meant to fill the existing gap and makes it possible to evaluate the economic benefit of an integrated GLONASS application for different fields.

Satellite information system malfunctions caused by broadband solar radio emission during solar flares

The paper briefly discusses the impairment of normal functioning of the global positioning system (GPS) and the global navigation satellite system (GLONASS) caused by broadband solar radio emission during large solar flares on October 28, 2003, and December 6 and 13, 2006.

Malaria on the World Wide Web.

The Internet is enabling scientists and clinicians in areas with endemic malaria to transfer information to scientists and clinicians in other countries. This should allow changes in therapy to follow the rapid changes in the disease that have posed such difficulties in the past. This article reviews Internet resources that focus on malaria. This includes 90 Web sites in 12 sections. Authoritative multinational organizational sites and regional sites, such as those in Africa, Asia (including Thailand and India), and South America (in Venezuela and Brazil), are described. Basic research-oriented databases, such as those that deal with plasmodia genomics, biochemistry, and vaccine development, as well as vector information and geographic satellite information systems, are reviewed. There is a section about malaria research-funding organizations that offer online applications. Useful teaching resources and journals, including those with full online access, are detailed.

Satellite Technology—A Farm Organization Perspective

The cost of information delivery and exchange is a concern for many organizations. The American Farm Bureau Federation began using a satellite data system in January 1989 to provide member organizations with a better, more robust communications network. Currently, 574 county offices located in four states plus 46 state Farm Bureau offices are part of the communications network. The video portion of the system is utilized for organizational messaging, including public policy issues, teleconferences, staff improvement, and electronic marketing of livestock. Another part of the system provides current market data, along with other less time-sensitive information, for individual member subscribers. This program is now operating for a significant number of Farm Bureau members in 18 states. The satellite information system enables American Farm Bureau Federation to service better the needs of its members.

Future space missions

An orbiting space factory, a self‐directed deep‐space exploration robot, a fully automated earth resources and environment monitor, and a lunar base that could grow through the self‐replication of many of its elements were examined in a space technology assessment workshop which looked at the next 25 years. The joint NASA/American Society of Engineering Education workshop, held this summer at the University of Santa Clara in California, selected and defined challenging space missions that would identify critical technology needs for future research and development. The workshop offered possible representative future missions rather than specific proposals.A highly versatile ‘intelligent’ satellite information system for most types of earth survey was suggested. Previous systems have produced huge masses of data because they record everything they see. The proposed information system would select and interpret data coming from its sensors to provide results tailored to specific needs.