Sofia (София, ˈsɔ.fi.ja), is the capital and largest city of the Republic of Bulgaria, with a population of 1,395,568 in the Capital Municipality. It is located in western Bulgaria, at the foot of the mountain massif Vitosha, and is the administrative, cultural, economic, and educational centre of the country.

One of the oldest cities in Europe, the history of Serdica-Sredets-Sofia can be traced back some 7000 years; prehistoric settlements were excavated in the centre of the present city, near the royal palace, as well as in outer districts such as Slatina and Obelia. The well preserved town walls (especially their substructures) from antiquity date back before the 7th century BC, when Thracians established their city next to the most important and highly respected mineral spring, still functioning today. Sofia has had several names in the different periods of its existence, and remnants of the city's millenary history can still be seen today alongside modern landmarks.

Names

Geography

Sofia's development as a significant settlement owes much to its central position in the Balkans. It is situated in western Bulgaria, at the northern foot of the Vitosha mountain, in the Sofia Valley that is surrounded by mountains on all sides. The valley is the largest one in the country with territory of and average altitude of . Three mountain passes lead to the city, which have been key roads since antiquity, connecting the Adriatic Sea and Central Europe with the Black and Aegean Seas.

A number of low rivers cross the city, including the Vladaiska and the Perlovska. The Iskar River in its upper course flows near eastern Sofia. The city is known for its numerous mineral and thermal springs. Artificial and dam lakes were built in the last century.

It is located northwest of Plovdiv, Bulgaria's second largest city, west of Burgas, west of Varna, Bulgaria's major port-cities on the Bulgarian Black Sea Coast. The city is situated at less than from the borders with three countries: from Kalotina on the Serbian border, from Gyueshevo on the frontier with the Republic of Macedonia and from the Greek border at Kulata.

Climate

History

Antiquity

Sofia was originally a Thracian settlement called Serdica, or Sardica, possibly named after the Thracian tribe Serdi. Around 500 BC another tribe settled in the region, the Odrysi, known as an ethnos with their own kingdom. For a short period during the 4th century BC, the city was ruled by Philip of Macedon and his son Alexander the Great.

Around AD 29, Serdica was conquered by the Romans. It became a municipium, or centre of an administrative region, during the reign of Emperor Trajan (98-117) and was renamed Ulpia Serdica.

It seems that the first written mention of Serdica was made by Ptolemy (around 100 AD).

Serdica (Sardica) expanded, as turrets, protective walls, public baths, administrative and cult buildings, a civic basilica, an amphitheatre - the City Council (Boulé), a large Forum, a big Circus (Theatre), etc. were built. When Emperor Diocletian divided the province of Dacia into Dacia Ripensis (at the banks of the Danube) and Dacia Mediterranea, Serdica became the capital of Dacia Mediterranea. The city subsequently expanded for a century and a half, it became a significant political and economical centre, moreso — it became one of the first roman cities where Christianity was recognized as an official religion (Еmperor Galerius). So it was only very natural that Constantine the Great called Serdica (Sardica) "My Rome".

Serdica was of moderate size, but magnificent as an urban concept of planning and architecture, with abundant amusements and an active social life. It flourished during the reign of Byzantine Emperor Justinian I, when it was surrounded with great fortress walls whose remnants can still be seen today.

The city was destroyed by the Huns in 447 but was rebuilt by Justinian and for a while called Triaditsa. | |- | |}

Middle Ages

Sofia first became part of the First Bulgarian Empire during the reign of Khan Krum in 809 after a long siege. Afterwards, it was known by the Bulgarian name Sredets and grew into an important fortress and administrative centre. After the fall of North-eastern Bulgaria under John I Tzimiskes' armies in 971, the Bulgarian Patriarch Damyan chose Sofia for his seat in the next year. After a number of unsuccessful sieges, the city fell to the Byzantine Empire in 1018, but once again was incorporated into the restored Bulgarian Empire at the time of Tsar Ivan Asen I.

From the 12th to the 14th century, Sofia was a thriving centre of trade and crafts. It is possible that it has been called by the common population Sofia (meaning "wisdom" in Ancient Greek) about 1376 after the Church of St. Sofia. However, in different testimonies it was called both "Sofia" and "Sredets" until the end of the 19th century. In 1382 Sofia was seized by the Ottoman Empire in the course of the Bulgarian-Ottoman Wars - after a long siege the city was captured with treason. The new name — Sofia, replaced the old one — Sredets, after the liberation of the city from Turkish rule in 1878. Quite a time after 1878 there was a strong will, expressed by Bulgarian committees, to keep the name Sredets, but the Russian administration accepted Sofia.

Ottoman rule

The town was seized for several weeks by Bulgarian haiduks in 1599. In 1610 the Vatican established the See of Sofia for Catholics of Rumelia, which existed until 1715 when most Catholics had emigrated. In the 16th century there were 126 Jewish households, and there has been a synagogue in Sofia since 967.

End of Ottoman Rule

Sofia was taken by Russian forces on 4 January 1878, during the Russo-Turkish War, 1877-78, and became the capital of the autonomous Principality of Bulgaria in 1879, which became the Kingdom of Bulgaria in 1908. It was proposed as a capital by Marin Drinov and was accepted as such on 3 April 1879. By the time of its liberation the population of the city was 11,649. For a few decades after the liberation the city experienced large population growth mainly from other regions of the country.

In 1925 the St Nedelya Church assault was carried out by the Bulgarian Communist Party which claimed the lives of 170 people and injured another 500.

During World War II, Sofia was bombed by Allied aircraft in late 1943 and early 1944, and was later occupied by the Soviet Union. As a consequence of the Russian occupation with the approval of the Allied countries USA, Great Britain, France, Bulgaria's government, which allied the country with Germany, was overthrown by a Communist revolution. Like Prague, Warsaw, Bucharest etc. Sofia became a capital of the Communist-ruled People's Republic (1944). The country did not lose territory, but lost vital and important connections with Bulgarian population abroad and all over the world. During that time the population of Sofia expanded at high rates, as a large emphasis was placed on the industrial development of the city — many new large factories and manufacturing plants were built in and around the city. That led to the creation of many new neighbourhoods and the expansion of the public transport network.

Administration

Municipalities of Sofia City:

Demographics

According to 1999 data, the whole Capital Municipality, with a population of 1,246,651 , had a population density of 917.8.

The ratio of women per 1,000 men was 1,114 and the rate of population ageing was 100.3. The birth rate per 1000 people was 7.9 and steadily declining in the last 15 years, the death rate reaching 12.2 and growing. The population was declining by 4.3 per cent. However, considerable immigration to the capital from poorer regions of the country, as well as urbanization, are the reasons Sofia's population is in practice increasing. 5.7 people of every one thousand were married (only heterosexual marriage is possible in Bulgaria) and the infant mortality rate was 11 dead babies per 1,000 born alive, down from 18.9 in 1980.

According to the 2001 census, Sofia's population is made up of 96% ethnic Bulgarians; among minority communities, nearly 18,000 (1.5%) officially identified themselves as Roma, 6,000 as Turkish, 3,000 as Russian, 1,700 as Armenian, and 1,200 as Greek.

The unemployment is significantly lower than in other parts of the country — 2.45% of the active population in 1999 and declining, compared to 7.25% for the whole of Bulgaria as of July 1, 2007 (also on the decrease). The large share of unemployed people with higher education, 27% as compared to 7% for the whole country, is a characteristic feature of the capital.

When Sofia was declared capital in 1879 it was the fifth-largest city in the country after Plovdiv, Ruse, Varna and Shumen. Plovdiv remained the most populous town in Bulgaria till 1892 when Sofia took the lead.

Culture

Music and nightlife

Yalta Club and Chervilo are among the most popular clubs in Bulgaria. Yalta Club has hosted some of the most popular DJs: Pete Tong, Axwell, Steve Angello, Dimitri From Paris, Tom Novy and many others.

Museums

Places of special interest

Sofia currently enjoys a booming film industry as the filming ground of several international film productions. Vitosha Boulevard, also called Vitoshka — ranked as the world's 22nd most expensive commercial street — represents numerous fashion boutiques and luxury goods stores and features exhibitions by world fashion designers. Sofia's geographic location, situated in the foothills of the weekend retreat Vitosha mountain, further adds to the city's specific atmosphere.

Tourist attractions

The masterplan for the Sofia underground includes three lines with a total of 47 stations. In recent years the marshrutka, a private passenger van, began serving fixed routes and proved an efficient and popular means of transportation by being faster than public transport but cheaper than taxis. As of 2005 these vans numbered 368 and serviced 48 lines around the city and suburbs.  There are some 6,000 licensed taxi cabs operating in the city and another 2,000 operating somewhat illegally. Low fares in comparison with other European countries, make taxis affordable and popular among a big part of the city population.

The Stratospheric Observatory for Infrared Astronomy (SOFIA), is a joint project of NASA and the German Aerospace Center (DLR). Universities Space Research Association (USRA) was awarded the prime contract by NASA in 1996 for development, operation of the observatory and management of the American part while the DSI (Deutsches SOFIA Institut) manage the German part (mainly science and telescope related).

Facility

Once ready for use, it is hoped that observing flights will be flown 3 or 4 nights a week for the next 20 years. SOFIA will be based at NASA's Dryden Flight Research Center at Edwards AFB, California (near Lancaster, CA).

The telescope

SOFIA uses a 2.5-meter reflector telescope, which has an oversized primary mirror (2.7 meters in diameter) in common with most large infra-red telescopes. The telescope looks out of a large door in the side of the fuselage near the airplane's tail, and will initially carry nine instruments for infrared astronomy at wavelengths from 1–655 micrometres and high-speed optical astronomy at wavelengths from 0.3–1.1 micrometres. Although SOFIA’s telescope is by far the largest ever to be placed in an aircraft, compared to normal ground-based research observatories it is only medium-sized.

The project also has its own mirror coating facility in Moffett Field allowing a fast recoating of the primary mirror.

DLR is responsible for the entire telescope assembly (whereas NASA is responsible for the plane). The manufacturing of the telescope was subcontracted to European industry (The telescope is German, the mirror is French-made and the secondary mirror mechanism is Swiss-made).

For each mission one interchangeable science instrument will be attached to the telescope. Two groups of general purpose instruments are available. In addition an investigator can also design and build a special purpose instrument.

The open cavity housing the telescope will be exposed to high-speed turbulent winds. In addition, the vibrations and motions of the aircraft introduce observing difficulties. The telescope was designed to be very light-weight, and the mount includes a system to isolate the instrument from vibration. The telescope cabin must be pre-cooled prior to aircraft takeoff so that the telescope matches the external temperature (thus avoiding thermally-induced shape changes). Prior to landing the cabin is flooded with nitrogen gas in order to avoid condensation of moisture on the chilled instrument.

The aircraft

The SOFIA aircraft is a Boeing 747SP with a distinguished history. It was originally acquired by Pan American World Airways and was delivered in May 1977. The "SP" designates that this is a special short-body version of the 747, designed for longer flights than the basic model. United Airlines purchased the plane in February 1986, and removed it from active service in December 1995. Two years later, NASA purchased it from United for use by the SOFIA project. A series of "baseline" flight tests were conducted in 1997 prior to heavy modification of the aircraft by L-3 Communications Integrated Systems of Waco, Texas for its new role as a flying astronomical observatory. A dismantled section from another 747SP was used as a full-size mock-up to ensure proper modification.

Pan Am had named this aircraft Clipper Lindbergh in honor of the famous aviator Charles Lindbergh. The aircraft was personally christened by Lindbergh's widow, Anne Morrow Lindbergh, on the occasion of the 50th anniversary of her husband's historic flight from New York to Paris in 1927, although the aircraft had been officially placed into service on May 6, 1977. Similarly, Lindbergh's grandson, Erik Lindbergh, re-christened the aircraft Clipper Lindbergh on May 21, 2007 at L-3's Waco facilities.

The telescope is mounted in the aft part of the aircraft behind a pressurized bulkhead. The telecope's focal point is located at a science instruments suite in the pressurized section. In the center of the aircraft is the mission control and science operations section, while the forward section hosts the education and public outreach area.

Project development

The first use of an aircraft for performing infrared observations occurred in 1965 when Gerard P. Kuiper used the NASA Convair 900 to study Venus. Three years later, Frank Low used the Ames Learjet to perform observations of Jupiter and nebulae. In 1969, planning began for mounting a telescope on an airborne platform. The goal of this instrument was to perform astronomy from the stratosphere, where there was a much lower optical depth from water vapor absorbing infrared radiation. This project was named the Kuiper Airborne Observatory, and it was dedicated on May 21, 1975. The telescope became instrumental in numerous scientific studies, including the discovery of the ring system around the planet Uranus.

The proposal for a larger aircraft-mounted telescope was officially presented in 1984, which called for a Boeing 747 to carry a three meter telescope. The preliminary system concept was published in 1987 in the Red Book. It was agreed that Germany would contribute 20% of the total cost, and they would provide the telescope. However, the reunification of Germany and budget cuts at NASA led to a five year slide in the project. NASA then contracted the work out to the Universities Space Research Association (USRA), and in 1996, NASA and DARA signed a memorandum of understanding for the building and operation of SOFIA.

The SOFIA telescope's primary mirror was manufactured out of Zerodur, a glass-ceramic composite produced by Schott AG that has almost zero thermal expansion. REOSC, the optical department of the SAGEM Group in France, performed weight reduction by milling honeycomb-shaped pockets out of the back. They finished polishing the mirror on December 14, 1999, achieving an accuracy of 8.5 nm over the optical surface. The hyperbolic-shaped secondary mirror was made out of silicon carbide, with polishing completed by May 2000.

During 2002, the main components of the telescope were assembled in Augsburg, Germany. These consisted of the primary mirror assembly, the main optical support and the suspension assembly. After successful integration tests were made to check the system, the components were shipped to Waco, Texas on board an Airbus Beluga aircraft. They arrived on September 4, 2002. SOFIA completed its first ground-based "on-sky" test on August 18-19, 2004 by taking an image of the star Polaris.

In February 2006, following delays, and costs which increased from US$185 million to $330 million,, NASA placed the project "under review" and suspended funding. On the 15 June 2006, SOFIA passed the review when NASA concluded that there were no insurmountable technical or programmatic challenges to the continued development of SOFIA.

The first school children to see it were students from Waco Montessori School.

The maiden flight of SOFIA took place on 26 April 2007 at the L-3 Integrated Systems' (L-3 IS) Waco, Texas facility. After a brief test program was conducted in Waco to partially expand the flight envelope and perform post-maintenance checks, the aircraft was moved to Edwards Air Force Base on May 31, 2007. The first phase of loads and flight testing was used to check the aircraft characteristics with the external telescope cavity door closed. This phase was successfully completed by January, 2008 at NASA-Dryden F.R.C.

In late 2008, the aircraft will undergo flight tests at high altitude cruising speed with the telescope door open. This test phase is scheduled to run through the middle of 2009, after which SOFIA will begin limited science observation flights. Normal science observation flights should begin in 2011 and the observatory is slated for full capability by 2014.

Scientific research

The primary science objectives of SOFIA are to study the composition of planetary atmospheres and surfaces; to investigate the structure, evolution and composition of comets; to determine the physics and chemistry of the interstellar medium; and to explore the formation of stars and other stellar objects.

References

External links

• USRA SOFIA website
• SOFIA Mission Profile by NASA's Solar System Exploration
• SOFIA Website des DLR (de)
• SOFIA on Astronomy Picture of the Day
• L-3 Communications Integrated Systems
• Evergreen International Airlines

See also

• Kuiper Airborne Observatory
• Infrared astronomy
• Far infrared astronomy