PARC GUELL

Leer más »

COLLIOURE

Collioure és un poblet coster amb un encant especial, ple de reminiscències de l'época medieval i un aspecte veritablement cuidat fins a l'últim detall, alegre i ple de color. Fets que li atorguen un aire de poblet de conte de fades, realment idíl·lic.

La riera de Collioure va a morir directament a la zona del port, zona on es troba el Castell Reial


Aquest és l'aspecte de la riera direcció muntanya. El dia era calurós i el sol brillava amb força

El port de Collioure, petitó i situal sota la protecció del Castell Reial. En altre época, Collioure va ser un punt estràtegic de la costa catalana i és per això que posseix una important xarxa de fortificacions

Vam tenir la sort de trobar una petita orquestra al carrer que donava una alegria afegida a la proporcionada pels colors vistosos de façanes, portes i finestres. La música inundava l'àmbient d'un aire festiu que impregnava tot el poble

A partir de l'any 981, els Comtes del Roselló i els Reis de Mallorca van començar a acondicionar i a fortificar Collioure, que va esdevenir entre 1276 i 1344 la residència d'estiu dels Reis de Mallorca. El Castell Reial del fons de la imatge n'era un dels elements principals d'aquesta fortificació

L'església de Collioure de Nostra Senyora dels Angels té els fonaments en constant contacte amb el Mar Mediterrani. El campanar, constuit durant l'edat mitjana, servia de far pel port

El Castell Reial de Collioure és la peça mestra del dispositiu de defensa. Principalement acondicionat pels Comtes del Rosselló i els Reis d'Aragó entre 1276 i 1344 va ser la seu de la cort dels Reis de Mallorca

El Sol primaveral va animar alguns banyistes a apropar-se a la platja més propera al Castell Reial, separada d'aquest pel port

Vista des d'un dels espigons del campanari de l'església i del Castell Reial. Veient aquesta vista, no puc evitar enrecordar-me de Cadaqués per la situació de les platges. No obstant, Cadaqués destaca pel blanc de les cases, i Collioure pel marró clar de la pedra

Els carrerons del casc antic de Collioure estan plens de color i són molt animats, sempre plens de gent passejant


Un altre carreró on podeu veure els colors alegres de les façanes i com d'estrets són


Des de l'entrada al Castell Reial és té una bona vista de l'església i d'una de les platges. Les façanes de pedra atorguen un aire medieval al poble força atractiu


Petit parc infantil al passeig marítim de Collioure

La vista des d'aquest passeig del Castell Reial, amb el malecon, i el campanar de l'església al fons era una de les millors d'aquest petit poble encantador

Vista bonica del Castell Reial i de l'església

En un lloc destacat del cementiri de Collioure descansa eternament Antonio Machado, el gran poeta espanyol i membre destacat de la generació del 98

Al seu lloc de descans, protegit i arropat per uns arbres que transformen l'escalfor d'un sol primaveral en un mini entorn càlid i íntim, cartes i dedicatòries vingudes principalment del seu país d'origen l'acompanyen en el seu viatge etern

Collioure és un petit poblet coster plenament encarat al mar Mediterrani, protegit a banda i banda per dos turons que li donen un aspecte molt recollit i compacte. En el seu moment va esdevenir un punt estratègic de la costa catalana i per això posseix un xarxa important de fortifcacions, com la que apareix timidament en l'extrem superior dret de la imatge

Aquest arbre donava una ombra agradable en aquesta tarda plenament primaveral, en un petit parc amb vistes privilegiades al port i a l'esgésia de Collioure

La posada del sol sobre l'església de Collioure, flanquejada per dos espigons, es podia veure així des d'un punt lleugerament elevat amb l'agradable i càlida sensació a la cara dels raigs tebis d'un sol ja donant el relleu a la lluna

Leer más »

POST 2

Leer más »

POST 1

Communications Satellites


In 500 years, when humankind looks back at the dawn of space travel, Apollo's landing on the Moon in 1969 may be the only event remembered. At the same time, however, Lyndon B. Johnson, himself an avid promoter of the space program, felt that reconnaissance satellites alone justified every penny spent on space. Weather forecasting has undergone a revolution because of the availability of pictures from geostationary meteorological satellites--pictures we see every day on television. All of these are important aspects of the space age, but satellite communications has probably had more effect than any of the rest on the average person. Satellite communications is also the only truly commercial space technology- -generating billions of dollars annually in sales of products and services.


The Billion Dollar Technology


Perhaps the first person to carefully evaluate the various technical options in satellite communications and evaluate the financial prospects was John R. Pierce of AT&T's Bell Telephone Laboratories who, in a 1954 speech and 1955 article, elaborated the utility of a communications "mirror" in space, a medium-orbit "repeater" and a 24-hour-orbit "repeater." In comparing the communications capacity of a satellite, which he estimated at 1,000 simultaneous telephone calls, and the communications capacity of the first trans-atlantic telephone cable (TAT-1), which could carry 36 simultaneous telephone calls at a cost of 30-50 million dollars, Pierce wondered if a satellite would be worth a billion dollars.

After the 1957 launch of Sputnik I, many considered the benefits, profits, and prestige associated with satellite communications. By the middle of 1961, NASA had awarded a competitive contract to RCA to build a medium-orbit (4,000 miles high) active communication satellite (RELAY); AT&T was building its own medium-orbit satellite (TELSTAR) which NASA would launch on a cost-reimbursable basis; and NASA had awarded a sole- source contract to Hughes Aircraft Company to build a 24-hour (20,000 mile high) satellite (SYNCOM).

Sputnik satellite, the first Satellite launched into space

By 1964, two TELSTARs, two RELAYs, and two SYNCOMs had operated successfully in space. This timing was fortunate because the Communications Satellite Corporation (COMSAT), formed as a result of the Communications Satellite Act of 1962, was in the process of contracting for their first satellite. On April 6, 1965 COMSAT's first satellite, EARLY BIRD, was launched from Cape Canaveral. Global satellite communications had begun.


The Global Village: International Communications


Some glimpses of the Global Village had already been provided during experiments with TELSTAR, RELAY, and SYNCOM. These had included televising parts of the 1964 Tokyo Olympics. Although COMSAT and the initial launch vehicles and satellites were American, other countries had been involved from the beginning. AT&T had initially negotiated with its European telephone cable "partners" to build earth stations for TELSTAR experimentation. Further negotiations in 1963 and 1964 resulted in a new international organization, which would ultimately assume ownership of the satellites and responsibility for management of the global system. On August 20, 1964, agreements were signed which created the International Telecommunications Satellite Organization (INTELSAT).

Three Crew Members Capture Intelsat VI

By the end of 1965, EARLY BIRD had provided 150 telephone "half- circuits" and 80 hours of television service. The INTELSAT II series was a slightly more capable and longer-lived version of EARLY BIRD. The INTELSAT III series was the first to provide Indian Ocean coverage to complete the global network. This coverage was completed just days before one half billion people watched APOLLO 11 land on the moon on July 20, 1969.

From a few hundred telephone circuits and a handful of members in 1965, INTELSAT has grown to a present-day system with more members than the United Nations and the capability of providing hudreds of thousands of telephone circuits. Cost to carriers per circuit has gone from almost $100,000 to a few thousand dollars. Cost to consumers has gone from over $10 per minute to less than $1 per minute. If the effects of inflation are included, this is a tremendous decrease! INTELSAT provides services to the entire globe, not just the industrialized nations.


New Technology


In the early 1960s, converted intercontinental ballistic missiles (ICBMs) and intermediate range ballistic missiles (IRBMs) were used as launch vehicles. These all had a common problem: they were designed to deliver an object to the earth's surface, not to place an object in orbit. Upper stages had to be designed to provide a delta-Vee (velocity change) at apogee to circularize the orbit. The DELTA launch vehicles, which placed all of the early communications satellites in orbit, were THOR IRBMs that used the VANGUARD upper stage to provide this delta-Vee. It was recognized that the DELTA was relatively small and a project to develop CENTAUR, a high-energy upper stage for the ATLAS ICBM, was begun. ATLAS-CENTAUR became reliable in 1968 and the fourth generation of INTELSAT satellites used this launch vehicle.

Atlas Centaur rocket launch. A rocket like this one launched the satellite Intelsat IV

The fifth generation used ATLAS-CENTAUR and a new launch-vehicle, the European ARIANE. Since that time other entries, including the Russian PROTON launch vehicle and the Chinese LONG MARCH have entered the market. All are capable of launching satellites almost thirty times the weight of EARLY BIRD.

Ariane V lift-off

In the mid-1970s several satellites were built using three-axis stabilization. They were more complex than the spinners, but they provided more despun surface to mount antennas and they made it possible to deploy very large solar arrays. The greater the mass and power, the greater the advantage of three-axis stabilization appears to be. Perhaps the surest indication of the success of this form of stabilization was the switch of Hughes, closely identified with spinning satellites, to this form of stabilization in the early 1990s.

Much of the technology for communications satellites existed in 1960, but would be improved with time. The basic communications component of the satellite was thr traveling-wave-tube (TWT). These early tubes had power outputs as low as 1 watt. Higher- power (50-300 watts) TWTs are available today for standard satellite services and for direct-broadcast applications. An even more important improvement was the use of high-gain antennas. Focusing the energy from a 1-watt transmitter on the surface of the earth is equivalent to having a 100-watt transmitter radiating in all directions. Focusing this energy on the Eastern U.S. is like having a 1000-watt transmitter radiating in all directions. The principal effect of this increase in actual and effective power is that earth stations are no longer 100-foot dish reflectors with cryogenically-cooled maser amplifiers costing as much as $10 million (1960 dollars) to build. Antennas for normal satellite services are typically 15-foot dish reflectors costing $30,000 (1990 dollars). Direct-broadcast antennas will be only a foot in diameter and cost a few hundred dollars.


Mobile Services


In February of 1976 COMSAT launched a new kind of satellite, MARISAT, to provide mobile services to the United States Navy and other maritime customers. In the early 1980s the Europeans launched the MARECS series to provide the same services. In 1979 the UN International Maritime Organization sponsored the establishment of the International Maritime Satellite Organization (INMARSAT) in a manner similar to INTELSAT. INMARSAT initially leased the MARISAT and MARECS satellite transponders, but in October of 1990 it launched the first of its own satellites, INMARSAT II F-1. The third generation, INMARSAT III, has already been launched.

An aeronautical satellite was proposed in the mid-1970s. A contract was awarded to General Electric to build the satellite, but it was canceled--INMARSAT now provides this service. Although INMARSAT was initially conceived as a method of providing telephone service and traffic-monitoring services on ships at sea, it has provided much more. The journalist with a briefcase phone has been ubiquitous for some time, but the Gulf War brought this technology to the public eye.

The United States and Canada discussed a North American Mobile Satellite for some time. In the next year the first MSAT satellite, in which AMSC (U.S.) and TMI (Canada) cooperate, will be launched providing mobile telephone service via satellite to all of North America.


Competition


In 1965, when EARLY BIRD was launched, the satellite provided almost 10 times the capacity of the submarine telephone cables for almost 1/10th the price. This price-differential was maintained until the laying of TAT-8 in the late 1980s. TAT-8 was the first fiber-optic cable laid across the Atlantic. Satellites are still competitive with cable for point-to-point communications, but the future advantage may lie with fiber-optic cable. Satellites still maintain two advantages over cable: they are more reliable and they can be used point-to-multi-point (broadcasting).

Cellular telphone systems have risen as challenges to all other types of telephony. It is possible to place a cellular system in a developing country at a very reasonable price. Long-distance calls require some other technology, but this can be either satellites or fiber-optic cable.


The LEO Systems


Cellular telephony has brought us a new technological "system"-- the personal communications system (PCS). In the fully developed PCS, the individual would carry his telephone with him. This telephone could be used for voice or data and would be usable anywhere. Several companies have committed themselves to providing a version of this system using satellites in low earth orbits (LEO).

The most ambitious of these LEO systems was Iridium, sponsored by Motorola. Iridium planned to launch 66 satellite into polar orbit at altitudes of about 400 miles. Each of six orbital planes, separated by 30 degrees around the equator, would contain eleven satellites. Iridium originally planned to have 77 satellites-- hence its name.


Prospect and Retrospect


Arthur C. Clarke's 1945 vision was of a system of three "manned" satellites located over the major land masses of the earth and providing direct-broadcase television. The inherent "broadcast" nature of satellite communications has made direct-broadcast a recurrent theme--yet one never brought to fruition. The problems are not technical--they are political, social, and artistic. What will people be willing to pay for? This is the question-- especially with the availability of 120-channel cable systems. Hughes is apparently about to enter this field and may encourage others to do the same. Only then will Clarke's prophetic vision be fulfilled.

There are currently six companies providing fixed satellite service to the U.S.: GE Americom, Alascom, AT&T, COMSAT, GTE, and Hughes Communications. They operate 36 satellites with a net worth of over four billion dollars. Each year from 10-20 communications satellites are launched valued at about $75 million each. The launch vehicles placing them in orbit have similar values. Both satellites and launch vehicles are multi-billion dollar businesses. The earth station business is equally large. Finally the communications services themselves are multi-billion dollar businesses. John R. Pierce was right--it would be worth a billion dollars.



A Selective Communications Satellite Chronology


* 1945 Arthur C. Clarke Article: "Extra-Terrestrial Relays"
* 1955 John R. Pierce Article: "Orbital Radio Relays"
* 1956 First Trans-Atlantic Telephone Cable: TAT-1
* 1957 Sputnik: Russia launches the first earth satellite.
* 1960 1st Successful DELTA Launch Vehicle
* 1960 AT&T applies to FCC for experimental satellite communications license
* 1961 Formal start of TELSTAR, RELAY, and SYNCOM Programs
* 1962 TELSTAR and RELAY launched
* 1962 Communications Satellite Act (U.S.)
* 1963 SYNCOM launched
* 1964 INTELSAT formed
* 1965 COMSAT's EARLY BIRD: 1st commercial communications satellite
* 1969 INTELSAT-III series provides global coverage
* 1972 ANIK: 1st Domestic Communications Satellite (Canada)
* 1974 WESTAR: 1st U.S. Domestic Communications Satellite
* 1975 INTELSAT-IVA: 1st use of dual-polarization
* 1975 RCA SATCOM: 1st operational body-stabilized comm. satellite
* 1976 MARISAT: 1st mobile communications satellite
* 1976 PALAPA: 3rd country (Indonesia) to launch domestic comm. satellite
* 1979 INMARSAT formed.
* 1988 TAT-8: 1st Fiber-Optic Trans-Atlantic telephone cable

This post is an extract from: Communications Satellites: Making the Global Village Possible by David J. Whalen

Leer más »