Part I of this report last month focused on individual countries and their contributions and achievements related to the microwave industry. But the continent as a whole plays a key role in all sectors including industrial, biomedical, military, aerospace and emerging wireless technologies. Since there is such a broad range of sectors, in Part II we will only focus on the technological development in Europe of two sectors: Satellite communications from the launch of Sputnik to the use of satellites for mobile communication and broadcast TV; and microwave radar, which has developed to span the vastly differing demands of conflicts from WWII to the fight against terrorism to more peaceful applications such as automotive.
Satellite Communications in Europe: A Historical Perspective
Warsaw University of Technology, Poland
Satellite communications is an important part of telecommunications, and the main function of satellite-based commercial systems, alongside navigation and Earth observation. A satellite placed in a geostationary orbit (GEO) fixed above the Earth has the capability to cover up to a quarter of the Earth’s surface (except for the polar regions) and to realize long distance transmissions between users separated by a distance of several thousands of kilometres.
Satellite communication systems offer many different services for different groups of users, independently from the terrestrial telecommunications infrastructure. In general, these services can be divided into two groups:
Services for stationary users
- Two-way transmission Fixed Satellite Services (FSS) and broadcast applications - Direct Broadcast Services (DBS)
- Broadcast of digital TV programmes in DVB-S and DVB-S2 standard
- International telephony connections
- Data transmission networks - i.e. Very Small Aperture Terminals (VSAT) networks
- Occasional transmissions
- Back-up for terrestrial systems
Services for mobile users - Mobile Satellite Services (MSS)
- Voice and low rate data transmission
- Broadcasting of radio programmes (XM Radio and Sirius in US)
- Future broadband interactive services — to realize communications, “anywhere and at any time”
Broadcasting of TV programmes to individual users—Direct To Home (DTH)—is a major driving force for satellite communications. Conversion to High Definition TV (HDTV) will be an additional impulse to growth as will multimedia broadband services for mobile users. Currently there are over 200 active communications satellites in GEO, with more than 100 in Low Earth Orbit (LEO).
Satellite Communications Development
The new satellite era dawned on 4th November 1957, when the first satellite, Sputnik-1, was launched by the USSR. From the very beginning, the use of satellites for military and commercial telecommunications was considered to be an important and promising application. Initial investigations were carried out both in the US and the USSR. The first experimental communications satellite SCORE, which stood for Signal Communications by Orbiting Relay Equipment, was launched in 1958.
Echo-1 satellite, a passive reflector realized as a 30 m balloon coated with aluminium and launched in 1960, was the first intercontinental satellite transmitting between stations in the US and Western Europe. However, Telstar-1, launched in 1962, was the first true communications satellite, with an active transponder working in C-band. This satellite was used to realize the first transmission of a TV signal between ground stations in the US and in Europe (the UK and France).
Because a satellite in low orbit moves above the Earth’s surface, and many satellites are necessary to provide continuous services, the next step was to investigate the use of satellites placed in GEO. In 1964, Syncom-3 was the first geostationary communications satellite to be launched, which was used to transmit TV signals from the Summer Olympic Games in Tokyo, Japan.
In 1964, the International Telecommunications Satellite Organization (INTELSAT) was established as an inter-governmental organization with 12 participating countries, but the number of members grew rapidly over the next few years. The main task of this organization was to design, develop, construct, establish, maintain and operate the space segment of global commercial satellite systems.
In 1965, Early Bird (Intelsat-1) was the first commercial communication satellite launched in GEO, and the new era of commercial satellite communications began. Early Bird was 38.5 kg spin stabilized spacecraft with 2 transponders with the capacity of 240 telephone channels or one TV channel for point-point connections between ground stations placed in the US and Europe. Due to the low power signal transmitted by the satellite, in the ground station, a very large parabolic antenna had to be used. In subsequent years, new generations of Intelsat satellites increased the number of available transponders.
At the same time the USSR developed its own satellite communications system to distribute TV programmes. Because a large part of the USSR territory lay in the polar region where GEO satellites cannot be operated, satellites placed in elliptical orbits were used—Molnia satellites.
The enormous growth in demand for satellite communications resulted in a plethora of operational satellites. In the 1970s, the regional satellite operators were established: INTERSPUTNIK for the USSR and Eastern Europe, and EUTELSAT for Western Europe. Also, the first national communications satellites were launched.
Technical developments of the 1970s and 1980s, which resulted in the increase of the satellite weight and supply power and the realization of low noise and high power microwave components, made it possible to use Ku-band and facilitate the significant reduction of antenna dimensions in the ground stations. Hence, the broadcasting of TV programmes, firstly to head-ends of cable television networks and then directly to individual users equipped with receiving terminals.
In 1991, SES ASTRA realized a new concept of collocation of many satellites in the same orbit position in order to increase the number of TV programmes accessible to the user without changing the orientation of the receiving antenna.
Digital transmission of TV programmes in the 1990s using the MPEG-2 compression standard was the next stage of development. It enabled the transmission of several digital programmes in the single transponder channel instead of one analogue programme, with comparable reception quality. This seriously increased the number of transmitted programmes available for the user.
With regards to the use of satellite communications to provide services for mobile users, 1979 saw the International Maritime Satellite Organization (INMARSAT) established to realize communication with ships using GEO satellites operating in L-band.
At the beginning of the 1990s, investigations into the development of satellite mobile telephony systems were launched and specifically the use of constellations of satellites placed in Low Earth Orbit (LEO) and Medium Earth Orbit (MEO), in order to improve the power budget of the radio link between the satellite and handheld user terminal, in comparison with GEO satellites.
Two systems: IRIDIUM and GLOBALSTAR started commercial services in 1999 and 2000, respectively. However, these systems hit financial problems caused by the high cost of system development and short predicted life time in comparison to GEO systems plus a severe lack of user take-up. As a result, the implementation of other systems using LEO and MEO orbits were terminated.
This coincided with developments in satellite technology at the end of the 1990s whereby high power satellites with large deployable antennas could be built, meaning that mobile satellite telephony systems could be realized using GEO satellites. Thus, two systems—THURAYA and ACES—were built.
Satellite Communications in Europe
After the experimental tests of satellite communications in the US at the beginning of the 1960s, it was evident that telecommunications could be one of the most promising commercial applications of satellite systems. However, European activity was non-existent in comparison to the US and the USSR, and at the beginning of the satellite communication era, the European effort was virtually insignificant, being limited to the building of ground stations in the UK and France and then in Germany and Italy.
To change this situation, two major initiatives were instigated, namely international projects coordinated by the European Space Agency (ESA) and its predecessors, the European Space Research Organization (ESRO) and European Launcher Development Organization (ELDO) and national projects.
In 1967 ESRO began studies on the technical feasibility and economic aspects of a European satellite communications system. It was deemed that going into competition with INTELSAT would be difficult so special applications for Europe were considered: intra-continental telephone connections (for the European Conference of Postal and Telecommunications Administrations - CEPT), distribution and exchange of TV programmes (for the European Broadcasting Union - EBU) and maritime communications.
In the early 1970s, a satellite communication system project was launched to consider the realization of an experimental satellite for the transmission of telephone calls and TV programmes [Orbital Test Satellite (OTS)] and a satellite for maritime communications [Maritime Orbital Test Satellite (MAROTS)].
At the same time, some countries started national or joint venture experimental communications satellite projects: SKYNET in the UK in cooperation with the US for military applications, SYMPHONY in Germany and France, and SIRIO in Italy. SYMPHONY-1, with two C-band transponders, was the first European communications satellite placed in GEO in 1974. In 1977, the ESA OTS-2 satellite was launched. This was the first communications satellite with Ku-band transponders capable of handling 7,200 telephone connections.
The first commercial European communications satellites were launched in 1981 [Maritime European Communication Satellite 1 (MARECS-1)] and in 1983 [European Communications Satellite 1 (ECS-1)]. MARECS-1 was the continuation and re-definition of the MAROT experimental programme and was used by INMARSAT. ECS-1 was the first of five satellites built by ESA and after the launch transferred to EUTELSAT as EUTELSAT I satellites.
In the 1980s and the 1990s, the next generations of EUTELSAT satellites, and also national communications satellites were launched, and European satellite communications began to play a significant role in the everyday life of citizens.
In the 1980s, the satellite broadcasting of TV programmes using telecommunications satellites with medium power transponders entered Europe by the back-door, avoiding the decisions of WARC 77, with the use of high power Ku-band broadcasting satellites. Only a few broadcast satellites were launched and used, with the bulk of satellite TV programmes being transmitted using Ku-band transponders of telecommunication satellites. Increases in the number of satellites and the transponders they carried increased the volume of programmes available to users. In 1985, SES ASTRA, the first European private satellite operator in Europe, was established, launching the ASTRA-1 satellite and offering TV programmes to individual users, thus becoming a rival to EUTELSAT.
The great success of European satellite communications operators was connected to the broadcasting of digital TV programmes using DVB-S standards. The family of DVB standards were proposed by the European Broadcasting Union (EBU) and the European Telecommunications Standard Institute (ETSI) in 1995 to realize the transmission of digital television in different media (satellite, cable and then terrestrial) in Europe. Over the next few years DVB-S, based on the MPEG-2 compression method, became the worldwide standard. In 1996, satellite digital television based on this standard was launched in Europe, and now over 1,000 digital TV programmes and several hundred digital radio programmes are transmitted by ASTRA’s satellites and EUTELSAT’s HotBirds.
The DVB-S standard is also used for data transmission, i.e. realization of access to Internet via satellite, supported by a return channel realized by terrestrial telephone networks or by a satellite in Ka-band using the DVB-RCS standard.
In 2003, the next version of the DVB-S2 standard, based on the MPEG-4 image compression method, and adaptive spectrum effective modulation schemes was announced and implemented. Using this standard, a larger number of TV programmes can be transmitted in a single transponder channel. This transition to the digital television standard is related to the increasing number of programmes and the introduction of HDTV services in Europe. The DVB-SH standard relates to the provision of multimedia data broadcasting services to mobile users. As for the near future, the new satellite applications of interactive broadband transmissions, operating in S- and Ka-bands, will be offered to mobile and fixed users, respectively. Also, new satellites will be equipped with multi-beam antennas and advanced modern transponders operating at increased power levels.
Microwave Radar in Europe: A Historical Perspective
Consulting engineer and author
When Microwave Journal was first published in July 1958, European electronics had scarcely recovered from the devastation of World War II. The industry needed to make up for lost time, be innovative and build on significant pre-war technological breakthroughs. These can be traced back to as early as the 1920s when European scientists were attracted by ‘Ultra High Frequencies’ and the unexplored world opening up beyond the 1 GHz border.
In 1923, Professor René Mesny went down to wavelengths of 1.2 m (250 MHz), and with his colleague, Pierre David, he organized a public demonstration of a radio link using such ‘short’ waves at the Physics and Wireless Telegraphy Exhibition in Paris, France. David had other applications in mind too, and as early as 1926 he started trials to detect airplanes by their electromagnetic radiation.
Next came Professor Heinrich Barkhausen of the Technical University of Dresden, Germany, who, with his colleague Kurz, reached the magical 30 cm limit with a triode fed in an unusual way: for their Positive Grid Tube they applied the high voltage to the grid instead of the traditional plate. This Barkhausen-Kurz oscillator is considered to be the first microwave oscillator.
In 1927, using a modified Barkhausen scheme, Professor Emile Pierret at the University of Nancy, France, reduced the wavelength to a new 12 cm record. During his tests he observed many effects of reflections in the cluttered yard of the faculty. Henri Gutton, a student who assisted him, would later remember these effects and deduce that a ship could be detected in this way. I shall explain later how he turned this idea into a radar reality.
The most spectacular achievement, however, was undoubtedly the link set up in 1931 across the Channel by an Anglo-French team from ITT, led by André Clavier. They demonstrated a focused beam—which they named a micro-ray—at 18 cm. Thus the advent of the European microwave pioneer was confirmed.
Magnetron: a European Success Story
In 1904, the German Christian Hülsmeyer failed in his project to provide shipping companies with his patented Telemobiloskop, which incidentally, could have saved the Titanic eight years later. For almost 30 years there were no significant microwave radar developments, all things being confined to the metric field due to the lack of sufficient powerful centimetric sources. However, in 1940 the definitive solution arrived in the form of the magnetron.
This valve had been envisaged in 1918 by the American A.W. Hull as a Lee de Forest’s triode competitor, but it was not used as an RF source until 1924 when the Czech August Žaček and the German Erich Habann succeeded in bringing it into oscillation. In his Praha laboratory, Žaček got a 29 cm wave with a sort of Barkhausen mounting, and Habann took it one step further at the Jena University by suggesting that Barkhausen’s negative resistance effect could be produced with a cylindrical fenced anode. This opened the way to a field of research that focused around three eminent European scientists: E.C.S. Megaw at GEC, UK, Klaas Posthumus at Philips NatLab, Netherlands, and Maurice Ponte at SFR-CSF, France.
Ponte began his magnetron research in 1932, with the aim of higher emitted levels and reduced magnetic fields. Pursuing Habann’s idea he found that cutting the anode in multiple paired segments divided the magnetic field required by the number of segments. Over the next five years he continued his anode geometry trials with Henri Gutton. In 1937 they reached a peak power of 10 W at 16 cm with a tube they named M-16.
Ponte was in contact with Megaw who was mostly involved in the theoretical question of multi-modes coexistence in a given valve. He pursued this work in open competition with Posthumus, author of a new theory that he had named rotating field oscillations. Apart from their theoretical debates, Posthumus also set up a split anode magnetron that delivered about 10 W at 30 cm in 1933.
These ‘first generation’ magnetrons, despite their limited performance, found immediate applications as radar sources. In Germany in 1933 the trials for a naval radar by Rudolf Kühnhold used a Posthumus magnetron giving 40 W at 48 cm. In France, a decimetric radar (16 cm) was installed on board the liner Normandy by Gutton, first (1935) with a positive grid triode and later (1937) with his M-16 magnetron. In Holland in 1936 detection tests ordered to C.H. Staal by the Koninklijke Marine used a 10 W, 30 cm Philips magnetron. With the levels available, only large targets—civil liners or warships—could be considered for these attempts. All these research programmes proved the need for improved power sources.
It is well documented that, in England, Robert Watson-Watt had deliberately, and for a time successfully, excluded microwaves to set his Chain Home on a decametric basis. But when the enemy turned to bombing by night, Chain Home was not accurate enough to direct night-fighters within their interception range, and the need for efficient AI radars quickly resumed the interest in centimetric waves.
The decisive turnaround came from Professor John Randall and his student Henry Boot at Birmingham University, UK, who in 1939 had the bright idea to substitute cylindrical cavities in place of the external oscillating circuits of traditional magnetrons and to cut those cavities in a large copper ring used as the anode. On February 21, 1940, a six cavity prototype gave 400 W at 9.9 cm. Their next magnetron (E-1188), produced on May 16, was calibrated to give at least 1 kW.
Its only defect was a very short lifespan, due to the fast evaporation of the directly heated tungsten filament they used as the cathode. The last word lay with Ponte, who on May 9, 1940, only two days before the German army broke through the front line and rushed to Paris, crossed the Channel with two samples of a new M-16 using an oxide coated and indirectly heated cathode. Bringing together the principles of the anode cavities and the oxide cathode, Megaw on June 26 achieved a 15 kW level, which exceeded all expectations. The cavity magnetron, disclosed three months later to the American allies by the Tizard mission, opened the way to the centimetric radar revolution, which was claimed to have changed the course of WWII.
Post-war European Radar
Directly after WWII and for the next three decades, radar together with microwave radio links, supported the revival of the European microwave industry. British companies such as Marconi, GEC, Plessey and Ferranti had the privilege of priceless experience acquired during the war. In 1948 Marconi was charged with a study for the complete overhaul of the RAF radar chain round the whole of the UK. However, this favourable period was followed by two decades without any significant public orders. British companies, without major government procurements, struggled against US and new European competitors on the export market. The success of the privately-developed Martello in the 1980s came probably too late, when the dramatic restructuring of the European defence industry arose after the fall of the Berlin Wall.
In other countries, companies such as CFTH (France) or Microlambda (Italy) entered the field without any radar background, and chose to start on a US licensed basis. CFTH’s first radars (a Precision Approach Radar, replica of the AN/MPN-1, and COTAL, a gun control radar issued from the SCR-584) were successful enough to give the company a solid position for markets of gun guidance (NATO Hawk programme, 1958); spatial trajectography (Aquitaine, 1955); and long-range 3D air surveillance systems. In 1963 CFTH won the NATO competition for equipping the NADGE long-range stations with its Palmier/ARES.
Microlambda opened in 1951 at Fusaro near Napoli in a pre-war torpedo factory, as a joint venture between the Italian holding Finmeccanica and Raytheon, to start a radar production business. The first apparatus transferred to Fusaro was the TPS-1D. The successful completion of the contract opened the way for Microlambda to develop in an autonomous way. It became Selenia, which received the Italian part of the NATO Hawk programme.
In the Netherlands Signaalapparaten (opened in 1922 at Hengelo) was a manufacturer of gun guidance systems. Captured by the Germans, and harshly damaged by allied raids, the factory reopened in 1945 to restart its original business. In the meantime radar had become a required element of Gun Laying systems. The task was given to Max Staal, who had installed, before the war, a 70 cm radar prototype on board the Dutch destroyer Isaac Sweers. As general manager of Signaal, Staal later produced a large range of successful radars for the Dutch Navy and for a worldwide export.
Named head of CSF, Ponte created a Radar Application Department in 1950 to take advantage of the pre-war experience of Gutton’s decimetric radars, and acquired know-how in magnetron applications. CSF was the first to respond to French government requests for Naval radars, but its most significant success occurred in the airborne radar domain, after it won the bid for the fighter Mirage 3C radar with its famous Cyrano (1958), from which more than 1,000 sets were sold over the next 20 years.
For many years all these companies were confronted by the lack of microwave components, which they had to develop themselves, or buy from new specialist companies such as EEV in the UK. Until the mid 1960s progress in radar meant longer ranges (more powerful transmitters), and increased resolution (larger antennas). In 1957 CFTH achieved a world record with an S-band klystron delivering 30 MW peak power. This trend slowed down when advances in signal processing gave priority to wideband components. In 1968 the same CFTH laboratory succeeded in reaching a 10 percent bandwidth at 200 kW average power.
In the meantime, Doppler filtering and pulse compression had been implemented. Pulse compression was patented during WWII by the German engineer E. Huttman (1940) but remained unapplied. In 1954, Charles E. Cook revived it at the US Sperry Co. for the AN/FPS35. It was not long before the idea came back to Europe: in March 1959, M.H. Carpentier at STTA, France, tested a laboratory model, which is said to be the second recorded in the world. In 1962 it was applied by CFTH to the experimental Conrad radar.
Active Antennas: Key to the New Multi-function Systems
In the ‘80s, R&D efforts considered the new concepts of phased arrays and electronic scanning, one major technical gap in radar development. It was not exactly a new idea, insofar as the WWII German Mammut was already an electronically scanned phased array. The concept was revived when size and weight of ABM early warning radars made mechanical scanning impracticable, and progressively it extended to complete radar families.
Three decades were necessary for making it technically workable, with two main ways of implementation:
- Passive Electronically Scanned Antennas (PESA) are powered by a single source sharing its output between many phase shifters plus transmitters modules. Power may be distributed to the radiating elements by a more or less complicated net of waveguide feeders, as implemented in the ‘80s French DRBJ11 or 22XX. In a more advanced architecture the power source may face an array of multiple phased reflectors (reflect array), or send its waves through an electronic lens. This solution, combined with a fast mechanical rotation, has been adopted both by Thales (Arabel) for the French SAAM anti-missile system and Selex (Empar) for the Horizon frigates PAAMS system.
- Active Electronically Scanned Antennas (AESA) feature the most advanced architecture. They use a large number of solid-state transmit/receive (T/R) modules, instead of the PESA single source. This improves beam agility and flexibility, saves energy and increases reliability. AESAs are specially suitable for multifunctional systems (to make a ground radar evolve from a general Air Defence mission to an extended Air and Missile Defence mission, for example.) First implementations were limited to an elevation ‘1D’ e-scanning, with a classical rotating mode for azimuths: MASTER-A (Thales, 1995) or RAT-31DL (Selex, 1999) are both fitted with horizontal rows of radiating elements, fed with a vertical column of solid-state phase-controlled transmit amplifiers.
Getting full ‘2D’ scanning required major investment. The UK Multi-function Electronically Scanned Adaptive Radar (MESAR) research programme was launched in 1982 jointly by Plessey and DERA. It resulted in an array of 1,264 elements, each delivering 10 W, quad-packed on a total of 316 T/R-modules. MESAR has initiated Sampson, an S-band Multi-Function Radar (MFR) produced by BAE Systems Insyte to be fitted to the PAAMS missile system of the Royal Navy’s Type 45 destroyers.
Sampson’s closest competitor is the Thales-NL X-band MFR Active Phased Array Radar (APAR), evolving from a Netherlands, Germany and Canada joint programme. As opposed to the Sampson’s two rotating arrays, it uses a four array fixed structure.
Other projects have been in conjunction with US companies: Counter Battery Radar (COBRA) was a 1997 tripartite programme for equipping French, British and German armies with battlefield AESA C-band radar. It was developed in just two years by the Euro-ART (Advanced Radar Technology) consortium including Thales Air Defence, EADS Deutschland GmbH, Thales Defence Ltd., and Lockheed-Martin, which brought its T/R solid-state GaAs technology. Today Thales works in association with Raytheon in a 50/50 joint venture, Thales-Raytheon Systems, which develops the M3R project, a very flexible system with a fully modular architecture of octopacks (8 T/Rs).
Airborne radars are basically multifunction systems; ensuring air surveillance, air-to-ground and weapon control missions, and AESA should logically be the most suitable choice. But it has suffered for some time from the lack of mass-produced X-band T/R modules. The Airborne Multirole Solid-state Active Array (AMSAR) programme was launched in 1992 in order to set up a technology demonstrator within GTDAR [a consortium between Thomson-CSF, GEC-Marconi Avionics and Daimler Benz Aerospace (now EADS)]. This tripartite programme began in 2003 with flight trials beginning in 2008.
However, markets don’t wait. To fit in with the Typhoon and Rafale fighter programmes, radar manufacturers had to provide interim solutions, respectively CAPTOR with a mechanical slotted antenna for the first, and RBE2 with an electronic lens PESA for the second. At the same time Thales studied a new 1000 T/R active antenna, based on AMSAR experience, featuring a ‘plug and play’ antenna to be included in a new RBE2-AA. Simultaneously, a Euroradar consortium, with Selex Sensors & Airborne Systems, Galileo Avionica —both united since May 2005 as Selex Galileo—EADS Defence Electronics, and INDRA made CAESAR, a 1425 T/R array to be plugged in an upgraded Captor-E CAESAR. AESA technology had become the de-facto standard for the radars of all advanced European fighters.
Technologically, active modules of an AESA are implemented with a limited number of monolithic integrated circuits, performing functions of phase shifter, microwave mixing, high power amplification, low noise amplification and T/R high frequency switching. More often HPA, LNA, attenuator and phase shifters use GaAs and the T/R switch uses a circulator. Today efforts lay in packaging, cooling, and compatibility with ‘tile’ antenna architectures. In the next five years, new components like GaN (which support higher power density and wider bandwidth) should be introduced for HPA and LNA, SiGe for phase shifters, and MEMS for power switching.
Providing radar manufacturers with adequate AESA components has become a top priority for the European microwave industry. It is a good opportunity to enforce Europe’s position in the highly competitive market of GaAs and other MMIC technologies. In return, radar should benefit to some extent from the mass production techniques developed for the consumer electronics market.
This Report began by relating the state of the European microwave industry in the early 1960s and posed questions as to how it had changed and developed during the intervening years. Of course, there are no definitive answers apart from the fact that the continent has had to adapt to political change, particularly in Eastern Europe and the expansion of the EU, economic pressures and competition from emerging markets such as India and China.
A stark reality is that against the background of changing markets and increased competition, companies have undergone rationalisation, merged or made acquisitions. In recent years the landscape of European microwave companies has changed with many of the household names that were synonymous with the industry being renamed, merged or gone completely. Now, companies are rarely single country flagships, but more likely part of large international organisations.
However, what has not changed and what has been illustrated in this Report is the wealth of industrial and academic expertise that is not only a part of Europe’s history, but is also its present and its future. Europe is at the forefront of technological development in many sectors. Through Europe-wide initiatives such as the Framework Programme (now in its 7th stage) and the associated Networks of Excellence Programmes, microwave research is taking an interdisciplinary and collaborative approach enabling system capabilities to guide the selection of new technologies. This is being backed up with financial investment and commercial development in an environment of coordination and cooperation at academic, industrial and political levels. Europe has a rich and valuable microwave history. That can continue if it focuses on exploiting its core competencies of a highly skilled research and development capability and the production of added value products and services.
The author would like to thank Józef Modelski and Yves Blanchard for their time and effort, and for sharing their knowledge and expertise.