Question: Bill Nelson flew as a Payload Specialist on a Space Shuttle launched for the first time in what year?

Context:
Payload specialist
A payload specialist (PS) is an individual selected and trained by commercial or research organizations for flights of a specific payload on a NASA Space Shuttle mission.
 People assigned as payload specialists included individuals selected by the research community, a company or consortium flying a commercial payload aboard the spacecraft, and non-NASA astronauts designated by international partners.
STS-61-C
STS-61-C was the twenty-fourth mission of NASA's Space Shuttle program, and the seventh mission of Space Shuttle "Columbia".
 It was the first time that "Columbia", the first operational orbiter to be constructed, had flown since STS-9.
 The mission launched from Florida's Kennedy Space Center on 12 January 1986, and landed six days later on 18 January.
 STS-61-C's seven-person crew included the second African-American shuttle pilot, future NASA Administrator Charles Bolden, the first Costa Rican-born astronaut, Franklin Chang-Diaz, and the second sitting politician to fly in space, Representative Bill Nelson (D-FL).
 It was the last shuttle mission before the Space Shuttle "Challenger" disaster, which occurred just ten days after STS-61-C's landing.
Byron K. Lichtenberg
Byron Kurt Lichtenberg, Sc.
 D. (born February 19, 1948) is an American engineer and fighter pilot who flew aboard two NASA Space Shuttle missions as a Payload Specialist.
 In 1983, he and Ulf Merbold became the first Payload Specialists to fly on the shuttle.
STS-51-G
STS-51-G was the eighteenth flight of NASA's Space Shuttle program, and the fifth flight of Space Shuttle "Discovery".
 The seven-day mission launched from Kennedy Space Center, Florida, on June 17, 1985, and landed at Edwards Air Force Base, California, on June 24.
 Sultan Salman Al Saud of Saudi Arabia was on board as a payload specialist; Al Saud became the first Arab, the first Muslim, and the first member of a royal family to fly into space.
 It was also the first Space Shuttle mission which flew without at least one astronaut from the pre-Shuttle era among its crew.
Space Shuttle Columbia
Space Shuttle "Columbia" (Orbiter Vehicle Designation: OV-102) was the first space-rated orbiter in NASA's Space Shuttle fleet.
 It launched for the first time on mission STS-1 on April 12, 1981, the first flight of the Space Shuttle program.
 Over 22 years of service it completed 27 missions before disintegrating during re-entry near the end of its 28th mission, STS-107 on February 1, 2003, resulting in the deaths of all seven crew members.
Dirk Frimout
Dirk Dries David Damiaan, Viscount Frimout (born 21 March 1941 in Poperinge, Belgium) is an astrophysicist for the European Space Agency.
 He flew aboard NASA Space Shuttle mision STS-45 as a payload specialist , making him the first Belgian in space .
Martin J. Fettman
Martin Joseph Fettman (B.S., D.V.M., M.S., Ph.D., Diplomate, ACVP) is an American pathologist and researcher who flew on NASA Space Shuttle mission STS-58 aboard the Space Shuttle Columbia as a Payload Specialist.
Bill Nelson
Clarence William Nelson II (born September 29, 1942) is an American politician and a member of the Democratic Party who serves as the senior United States Senator from Florida, in office since 2001.
 Nelson began his career in the Florida House of Representatives, where he served from 1972 to 1978.
 He then served in the United States House of Representatives from 1979 to 1991.
 In January 1986, Nelson became the first sitting member of the United States House of Representatives to fly in space.
 He flew as a Payload Specialist on the Space Shuttle "Columbia".
Shuttle Radar Topography Mission
The Shuttle Radar Topography Mission (SRTM) is an international research effort that obtained digital elevation models on a near-global scale from 56° S to 60° N, to generate the most complete high-resolution digital topographic database of Earth prior to the release of the ASTER GDEM in 2009.
 SRTM consisted of a specially modified radar system that flew on board the Space Shuttle Endeavour during the 11-day STS-99 mission in February 2000, based on the older "Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar" (SIR-C/X-SAR), previously used on the Shuttle in 1994.
 To acquire topographic data, the SRTM payload was outfitted with two radar antennas.
 One antenna was located in the Shuttle's payload bay, the other – a critical change from the SIR-C/X-SAR, allowing single-pass interferometry – on the end of a 60-meter (200-foot) mast that extended from the payload bay once the Shuttle was in space.
 The technique employed is known as interferometric synthetic aperture radar.
Albert Sacco
Albert Sacco Jr. (born May 3, 1949) is an American chemical engineer who flew as a Payload Specialist on the Space Shuttle Columbia on shuttle mission STS-73 in 1995.

Answer: 1981