COST 271 Action – Effects of the upper atmosphere on terrestrial and Earth-space communications : introduction

The COST 271 Action («Effects of the Upper Atmosphere on Terrestrial and Earth-space Communications») within the European ionospheric community has the objectives, embodied in the Memorandum of Understanding (MoU): to study the influence of upper atmospheric conditions on terrestrial and Earth-space communications, to develop methods and techniques to improve ionospheric models over Europe for telecommunication and navigation applications and to transfer the results to the appropriate Radiocommunication Study Groups of the International Telecommunication Union (ITU-R) and other national and international organizations dealing with the modern communication systems. This introductory paper summarises briefly the background and historical context of COST 271 and outlines the main objectives, working methods and structure. It also lists the participating countries and institutions, the Management Committee (MC) Meetings, Workshops and Short-term Scientific Missions. In addition, the paper discusses the dissemination of the results and the collaboration among the participating institutions and researchers, before outlining the content of the Final Report.


BACKGROUND AND HISTORICAL CONTEXT
Temporal and spatial changes in the upper atmosphere can act to limit and degrade the performance of terrestrial and Earth-space radio systems in many different ways.Command, control and communication systems involving transionospheric propagation may be disrupted; global positioning networks compromised and surveillance (optical and radar) systems affected.In addition, conditions in near-Earth space have other adverse effects on modern technology, ranging from the tracking and the lifetimes of satellites to the induction of damaging currents in power grids and transcontinental pipelines.The vulnerabilities of systems to changes in the upper atmosphere incorporate many different aspects.These include: space-weather effects on communication, navigation and surveillance systems; solar cycle phenomena and their impact on operational systems; modelling, forecasting, and prediction services; ionosonde sounder methods and measurements; applications of ionospheric tomography; transionospheric effects including scintillation; ionospheric propagation for high frequency communication systems; longwave propagation systems and effects; Global Positioning System (GPS) and ionospheric Total Electron Content (TEC) studies.The European ionospheric community has long been aware that co-operative research on an international basis is essential to deal with such complex issues.In particular, international co-operation is required for the collection of data, in both real-time and retrospective modes, the development and verification of new methods to improve the performance of both operational and future terrestrial and Earth-space communications systems and the exchange of expertise on space plasma effects on Global Navigation Satellite Systems (GNSS).
COST (the French acronym for «Co-operation in the field of Scientific and Technical Research») is an intergovernmental mechanism that sponsors scientific and technical co-operation and co-ordination between research teams and institutional partners from the 34 COST countries and with non-European institutions.COST 271 on «Effects of the Upper Atmosphere on Terrestrial and Earth-Space Communications» is an Action within the Telecommunications Information Science and Technology (TIST) Technical Committee.It is a four-year project that started in August 2000 to work collaboratively on the topics outlined above.The core of COST 271 Action has been a dynamic group of more than 100 active participants from 17 COST countries, 3 non-COST institutions and the European Space Agency (ESA), working as a technical community towards a common goal.The primary objective was to examine an area of research that had been given recent impetus by an increased technological interest in terrestrial and satellite radio communications and navigation (Zolesi and Cander, 2002).COST projects are well suited to developing research co-operation in fields where finance is provided at the national level, because the resultant benefits to the sponsors of work are greater than accrue from the efforts of individual organisations.The success of this approach has been demonstrated in the telecommunications domain in previous COST Actions concerned with the prediction of ionospheric propagation characteristics.
The earlier COST Actions relating to ionospheric radio propagation were particularly useful in creating a critical mass of researchers in projects where the initial emphasis was on long-term ionospheric prediction and retrospective ionospheric modelling over Europe.The COST 238 Action PRIME (Prediction and Retrospective Ionospheric Modelling over Europe) was a four-year research project with objectives to develop regional maps and models of the European ionosphere that are more accurate than internationally available global maps and models (Bradley, 1995).It involved the participation of some 72 scientists and engineers from 31 organisations in 17 nations.The work encompassed the production of regional monthly median maps and algorithms for generating 'instantaneous' snapshot maps of the standard vertical-incidence ionospheric characteristics from coordinated sounding measurements within Europe.Additional studies involved height profiles of electron density, the vertical total electron content up to an altitude of 1000 km and research leading to an improved understanding and thus potential for better modelling of ionospheric storm morphologies.Work conducted within COST 238 was continued in the follow-on project COST 251 IITS (Improved Quality of Service in Ionospheric Telecommunication Systems Planning and Operation) on the application of PRIME results in the improved quality of service in ionospheric telecommunication systems planning and operation (Hanbaba, 1999).
Both projects yielded significant results, but they also identified further areas where future development was needed.The topics for more research included: hour-to-hour and day-to-day variability prediction capabilities in the topside ionosphere, upgrading of the current models to include scintillation effects, the prediction of the ionospheric and plasmaspheric effects on navigational systems and the development of methods for calculating the reliability and compatibility of HF radio systems using digital modulation techniques and over the horizon HF backscatter radars (Zolesi and Cander, 2003).
The COST 271 Action was then established with a remit to examine a range of relevant research areas within four broad groupings.

COST 271 ACTION OBJECTIVES
COST 271 is an Action for the promotion, stimulation and co-ordination of the European research in ionospheric and plasmaspheric areas.The Memorandum of Understanding laid out the main objectives of the COST 271 Action as follows: -To perform studies to influence the technical development and implementation of new communication services, particularly for the GNSS and other advanced Earth-space and satellite-to-satellite applications.
-To develop methods and algorithms to predict and minimise the effects of ionospheric perturbations and variations on communications and to ensure that the best models over Europe are made available to the ITU-R.
-To collect additional and new ionospheric and plasmaspheric data for nowcasting and forecasting purposes.
-To stimulate further co-operation in the domain of ionospheric and plasmaspheric prediction and forecasting for terrestrial and Earth-space communications, including interactive repercussions on the corresponding standards in this field, taking into account the present and future needs of users.

COST 271 WORKING METHOD AND STRUCTURE
At the outset of the project consideration was given to a wide range of technical questions of practical relevance.In addition, a special issue of the journal Quaderni di Geofisica (Cander and Zolesi, 2001) was published at an early stage.The aim was assess the current state of knowledge and to outline the activities in each participating country in the work areas of the COST 271 Action, with an indication of their significance.The research within COST 271 was then organised within four Working Groups arranged into at total of 15 Work Packages that are shown in table I.The activities within each of these areas are documented fully in the papers that follow in this volume that serves to make up the Final Report of the COST 271 Action.on terrestrial and satellite-to-satellite communications. communications.

Working Group 1: impact of variability of space environment on communications
Space weather and its impact on terrestrial and space communications have drawn increasing attention in recent years.Four working packages were defined under this heading: Impact of space weather on communication -To identify present and future anticipated terrestrial and Earth space radio systems, to identify propagation phenomena which can lead to impairments of these radio systems that need to be modelled, to identify those space weather parameters that impact adversely and significantly on propagation conditions and to develop mitigation techniques.
Real-time satellite and terrestrial measurements for nowcasting, forecasting and warning purposes -To establish a space weather database consisting of both past and new measurements and to use these measurements for the development of now-casting and forecasting propagation procedures and software tools.
Long-term trends in the ionosphere and upper atmosphere parameters -To investigate and understand the nature of the long-term behaviour of all ionospheric regions and potential effects of the long-term trends on prediction models.
Upper atmosphere parameters monitoring for nowcasting and forecasting purposes -To develop methods to extract thermospheric parameters using routine ionospheric observations and to develop a version of the Self-Consistent method which would use routine electron density ionosonde profiles to monitor the upper neutral atmosphere above Europe.Some initial activities on improved robustness of prediction, which were separated as additional work packages at the beginning of the investigation, were later incorporated into the studies of real-time satellite and terrestrial measurements for nowcasting, forecasting and warning purposes.

Working Group 2: assessment of space plasma effects for satellites applications
The distribution and dynamics of the ionospheric plasma have a significant impact on GNSS applications for navigation, positioning and remote sensing of the Earth's atmosphere.Three working packages were included in this area: Plasma effects on GNSS applications -To explore the amplitude and dynamics of horizontal structures in TEC by combining data derived by different measuring techniques (ground-and spacebased GPS, NNSS, satellite altimetry), in particular under perturbed ionospheric conditions, to detect and analyse TID's and the resultant phase fluctuations that degrade accuracy in GNSS applications under various geophysical conditions.
Assessment of plasma propagation errors in navigation systems and merits and shortcomings of novel data sources -To assess ionospheric effects in non-ionospheric applications of GNSS signals, a) ionospheric influences in the use of GNSS occultation for stratosphere/troposphere applications, b) the effects of higher order ionospheric propagation errors in advanced ground based applications, like water vapour retrieval.
Investigation of extremes of ionization -To deal with observations aimed to come up with reasonable occurrence statistics when possible, to guide the data collection, to collect well-documented extremes and to provide a list of criteria to define type and nature of the extreme cases.

Working Group 3: ionospheric effects on terrestrial communications
Additional knowledge of the effects of large-scale ionospheric fluctuations, small-scale ionospheric irregularities, noise and interference with terrestrial communications including remote sensing, radio location techniques and radar is required.Four working packages were established within this general area: Effects of large-scale fluctuations on terrestrial communications -To determine at regional/global scale the percentage contribution to the variability of main ionospheric parameters.
Effects of small-scale ionospheric irregularities, interference and noise on terrestrial communication, including remote sensing, radio localization and radar -To give a definition of the classes of irregularities to be taken into account, an analysis of their effects on the performances of the systems, the establishment of a catalogue of the known characteristics and of the available equipment for the studies.
Mid-latitude ionospheric features in radio propagation models -To assess the role of ionospheric and plasmaspheric irregularities of various dimensions in radio propagation at middle latitudes.
Development of methods and algorithms to minimize the above-referred effects on terrestrial communications, including remote sensing, radio localization and radar -To identify the most important problems due to the ionospheric characteristics and variability, to develop possible methods, if any, to minimize the deleterious effects and when possible, propose specific algorithms.

Working Group 4: space plasma effects on Earth-space and satellite-tosatellite communications
Space plasma variability and irregularities effects are of increasing interest to the practical operation of satellite systems.Four working packages were included in this topic: Effects of space plasma variability and irregularities on Earth-space and satellite-to-satellite communication channels -To develop a database of space plasma variability and irregularities characteristics, using both measurements and results from theoretical models and to review the effects of variability and irregularities on communications, considering different locations of transmitter and receiver.
Development of algorithms and software to treat with disturbances in Earth-space and satelliteto-satellite communications -To forecast TEC in time and space from 1 to 24 h in advance by using neural networks, signal processing and other relevant techniques and to obtain quantitative description of the TEC variability and develop algorithms for nowcasting and forecasting.
Application of theoretical considerations to the study of space plasma effects -To study the ionospheric disturbances generated by natural electromagnetic and electrostatic instabilities.
Effects of the electron density vertical and horizontal gradients on satellite communications -To assess the effect of electron density gradients in the slant to vertical time delay conversion in Earth-space communications, to assess the effect of electron concentration gradients in satellite-to-satellite communication, to validate and improve existing topside electron concentration models by using the large Russian topside profiles database and to validate models of electron concentration profiles based on instantaneous (nowcasting) maps of basic parameters from vertical soundings data by using IGS slant TEC data and tomographic reconstruction.leading role in Working Party SG3L (Ionospheric Propagation).Further steps are planned to make the most applicable results of the Action available to ITU-R.Close links have also been established with several organizations that deal with GNSS (at present mainly GPS) applications for navigation and surveying.There is a strong involvement of Action members in ESA/ESTEC projects: a) concerning EG-NOS and GALILEOSAT and b) in connection with assessment studies for the use of GNSS occultation for atmospheric and ionospheric research.There is an active collaboration of group members in INTAS projects with Russian and Ukrainian participation.Another ongoing collaboration involves the International Reference Ionosphere (IRI) Working Group, with international Task Force Activities being carried out at the Abdus Salam ICTP on improvements to the IRI model.
Participants in COST 271 have made a considerable contribution to the international HIgh RAte Campaign (HIRAC) of the International GPS and in the validation of CHAMP results.They are also involved in the DIAS (Digital Upper Atmosphere Server) eContent framework activity and the ROSE project on establishing an international geophysical observatory at Gaudos.

OUTLINE OF THE REPORT
This COST 271 Final Report, published as a supplement to the international journal Annals of Geophysics, is organised in five Sections.
The First Section comprises this Introduction that contains the COST 271 Action background and historical context, the general objectives and priorities agreed in the Memorandum of Understanding, the working methods and structure, the participating countries and institutions, information about the MC meetings, workshops and short-term scientific missions, dissemination of results and finally the scientific and technical cooperation The Second Section contains 18 scientific papers concerning the main activities and results achieved in the four Working Groups of COST 271.Each paper is in the form of an independent review of one of the activities of the Action with an introduction, discussion of the results and references.
Four scientific papers, in which each WG Leader reviews the main achievements obtained in their respective areas of responsibility, make up the Third Section of the report, together with an additional paper containing some latest results.
The Fourth Section summarises the main achievements of COST 271 as a whole in the context of the MoU requirements and looks to the way ahead.Significant achievements have been made, developing out understanding of the issues and relevance of field and offering new knowledge that will serve to increase economic and social development.In addition, new challenges have been identified and a concrete proposal is outlined for a follow-on from COST 271.
The Fifth Section comprises a joint paper by two internationally recognized experts, not directly involved in the Action, who provide a final comment on COST 271.In particular, they assess the results within the context of the research activities in the other parts of the world, their importance to ITU-R and the IRI and consider the future for this area of radio science and its applications.
The Final Report is addressed primarily to those in the MoU signatory countries involved in frequency planning, spectrum management and system design; to those who sponsored the work undertaken; to industrial partners concerned with the technology who will learn from the results and to those in national radio regulatory administrations and international planning.In addition, the report is of interest to students of radiowave communication and navigation and others in the propagation research community.

Table I .
COST 271 Action structure.