Question: Which mission was completed first, Cos-B or Uhuru?

Context paragraphs:
Smith-class destroyer: The Smith"-class destroyers were the first ocean-going destroyers in the United States Navy, and the first to be driven by steam turbines instead of the reciprocating engines fitted in the sixteen earlier and much smaller torpedo boat destroyers ordered in 1898.  "Flusser" and "Reid" are sometimes considered to be Flusser"-class ships.  Also, since "Flusser" was completed first, some period documentation refers to the entire class as "Flusser"s.

Central Plaza Complex: The Central Plaza Complex consists of three commercial office buildings located in the Central Business District of Brisbane, Queensland, Australia.  The complex was constructed in three phases with Central Plaza 1 completed first in 1988, followed by Central Plaza 2 in 1990 and Central Plaza 3 in 2008.  Central Plaza 1 is the tallest of the three buildings, as well as the fifth tallest building in Brisbane.

Roosevelt Bridge (Florida): The Roosevelt Bridge is a major highway segmental bridge across the St. Lucie River in Stuart, Florida.  Carrying U.S. Route 1 (Federal Highway; unsigned State Road 5), it was built to supersede the old Roosevelt Bridge, which had twin parallel drawbridges, one for northbound traffic (opened in 1934, ) and the other for southbound (opened in 1964, ).  The new bridge, completed in 1996, is raised and much longer than the older twin drawbridges.  The southbound span of the old bridge is still functional for road and boat traffic and now carries two-way road traffic for what is now known as Dixie Highway, County Road 707.  The new high-level Roosevelt Bridge is approximately one mile long and is made of two three-lane sections running parallel to each other.  The northbound bridge was completed first, and housed two lanes of both north and south-bound traffic until the second bridge was finished.

Nevada City Firehouse No. 2: Nevada City Firehouse No. 2 is a historic firehouse located at 420 Broad Street in Nevada City, California.  Built in 1860-61, the firehouse was the first built in Nevada City.  At the time, Nevada City had two factions competing for public funds for a firehouse: the Broad Street fire company and a group based on Main Street.  While the Main Street company officially organized a day before the Broad Street company, the Broad Street firehouse had more private funding and was completed first, and hence Firehouse No. 2 became the first in the city.  The firehouse features a two-story portico in front and a Greek Revival cornice.

Uhuru (satellite): Uhuru was the first satellite launched specifically for the purpose of X-ray astronomy.  It was also known as the X-ray Explorer Satellite, SAS-A (for "Small Astronomy Satellite" A, being first of the three-spacecraft SAS series), SAS 1, or Explorer 42.  The observatory was launched on December 12, 1970 into an initial orbit of about 560 km apogee, 520 km perigee, 3 degrees inclination, with a period of 96 minutes.  The mission ended in March 1973.  Uhuru was a scanning mission, with a spin period of ~12 minutes.  It performed the first comprehensive survey of the entire sky for X-ray sources, with a sensitivity of about 0.001 times the intensity of the Crab nebula.

French ironclad Couronne: The French ironclad "Couronne" ("Crown") was the first iron-hulled ironclad warship built for the French Navy in 1859–62.  She was the first such ship to be laid down, although the British armoured frigate HMS "Warrior" was completed first.  The ship participated in the Franco-Prussian War of 1870–71, but saw no combat.  She was served as a gunnery training ship from 1885 to 1908 before she was hulked the following year and became a barracks ship in Toulon.  "Couronne" was scrapped in 1934, over 70 years after she was completed.

String Trio (Schubert): Franz Schubert wrote three string trios, all of them in the key of B-flat major.  From the first of these, D 111A, a trio Schubert wrote in 1814, only a few measures are extant.  The string trio D 471 consists of a completed first movement and an incomplete second movement, composed in 1816.  The last of these trios, D 581, was completed in four movements, exists in two versions and was composed in 1817.

2013 FC Bunyodkor season: The 2013 season was Bunyodkors 7th season in the Uzbek League in Uzbekistan.  Bunyodkor completed first treble in the season.  They completed a Domestic double winning both the League and Cup.  Also Bunyodkor youth team won "2013 Uzbek Youth League".  Bunyodkor also competed in the AFC Champions League, reaching the Round of 16 stage before being knocked out by Buriram United of Thailand.

Greg Mail: Gregory John Mail (born 29 April 1978, Penrith, New South Wales) is a batsman for the New South Wales Blues.  A tall opening batsman with a solid technique, he debuted for New South Wales in 1999-2000, and was awarded the prestigious Bradman Scholar award in 2000.  His most successful season was 2003-04, after which he has struggled to hold a place in the first XI.  Of the 12 occasions that a NSW player has carried their bat through a completed First Class innings and the 16 occasions that a player has scored a century in each innings of a First Class match, Mail is the only NSW player in history to have achieved both of these feats during his career.

Cos-B: COS-B was the first European Space Research Organisation mission to study cosmic gamma ray sources.  COS-B was first put forward by the European scientific community in the mid-1960s and approved by the ESRO council in 1969.  The mission consisted of a satellite containing gamma-ray detectors, which was launched by NASA on behalf of the ESRO on August 9, 1975.  The mission was completed on April 25, 1982, after the satellite had been operational for more than 6.5 years, four years longer than planned and had increased the amount of data on gamma rays by a factor of 25.  Scientific results included the 2CG Catalogue listing around 25 gamma ray sources and a map of the Milky Way.  The satellite also observed the X-ray binary Cygnus X-3.

Supporting paragraphs: Cos-B Uhuru (satellite)
Answer: Uhuru