Question: Which astronaut flew on more space missions, Piers Sellers or Jean-Jacques Favier?

Context paragraphs:
NewSpace: NewSpace—formerly alt.space; also new space, entrepreneurial space, astropreneurship, and commercial space—are umbrella terms for a movement and philosophy encompassing a highly visible, globally emerging, private spaceflight industry.  Specifically, the terms are used to refer to a global sector of relatively new, distinctly commercially minded, aerospace companies and ventures working to independently (of governments and their prime or major contractors, i.e., Old Space) develop faster, better, and cheaper access to space, space and spaceflight technologies, and overall space missions—again, all largely driven by commercial, as distinct from political or other, motivations (although many view the commercial aspects of NewSpace as simply the best means to broader, more socioeconomically-oriented, NewSpace ends; notably, the settlement of Mars and space colonization).  These terms also naturally extend to the worldwide community of designers, refiners, promoters, and advocates of building-block concepts, architectures, systems, technologies, missions, programs, protocols, and policies that enable and support NewSpace activities across all relevant dimensions.

Jean-Loup Chrétien: Jean-Loup Jacques Marie Chrétien (born 20 August 1938) is a French retired "Général de Brigade" (brigadier general) in the "Armée de l'Air" (French air force), and a former CNES spationaut.  He flew on two Franco-Soviet space missions and a NASA Space Shuttle mission.  Chrétien was the first Frenchman and the first western European in space.

European Astronaut Corps: The European Astronaut Corps is a unit of the European Space Agency (ESA) that selects, trains, and provides astronauts as crew members on U.S. and Russian space missions.  As of Nov 2014, 24 ESA astronauts are now able to go board the ISS.  There are currently 47 members of the Corps, 26 currently active.  The European Astronaut Corps is based at the European Astronaut Centre in Cologne, Germany.  They can be assigned to various projects both in Europe (at ESTEC, for instance) or elsewhere in the world, at NASA Johnson Space Center or Star City.

Claude Nicollier: Claude Nicollier (born 2 September 1944 in Vevey, Switzerland) is the first astronaut from Switzerland.  He has flown on four Space Shuttle missions.  His first spaceflight (STS-46) was in 1992, and his final spaceflight (STS-103) was in 1999.  He took part in two servicing missions to the Hubble Space Telescope (called STS-61 and STS-103).  During his final spaceflight he participated in a spacewalk, becoming the first European Space Agency astronaut to do so during a Space Shuttle mission (previous ESA astronauts conducted spacewalks aboard "Mir", see List of spacewalks and moonwalks 1965–1999).  In 2000 he was assigned to the Astronaut Office Extravehicular Activity Branch, while maintaining a position as Lead ESA Astronaut in Houston.  Nicollier retired from ESA in April 2007.

Discovery Program: NASA's Discovery Program is a series of lower-cost (as compared to New Frontiers or Flagship Programs), highly focused American scientific space missions that are exploring the Solar System.  It was founded in 1992 to implement then-NASA Administrator Daniel S. Goldin's vision of "faster, better, cheaper" planetary missions.  Discovery missions differ from traditional NASA missions where targets and objectives are pre-specified.  Instead, these cost-capped missions are proposed and led by a scientist called the Principal Investigator (PI).  Proposing teams may include people from industry, small businesses, government laboratories, and universities.  Proposals are selected through a competitive peer review process.  All of the completed Discovery missions are accomplishing ground-breaking science and adding significantly to the body of knowledge about the Solar System.

Apollo TV camera: The Apollo TV Camera refers to several television cameras used in the Apollo program's space missions, and on the later Skylab and Apollo-Soyuz Test Project missions, in the late 1960s and 1970s.  These cameras varied in design, with image quality improving significantly with each successive model.  Two companies made these various camera systems: RCA and Westinghouse.  Originally, these slow-scan television (SSTV) cameras, running at 10 frames-per-second (fps), produced only black-and-white pictures and first flew on the Apollo 7 mission in October 1968.  A color camera — using a field-sequential color system — flew on the Apollo 10 mission in May 1969, and every mission after that.  The Color Camera ran at the North American standard 30 fps.  The cameras all used image pickup tubes that were initially fragile, as one was irreparably damaged during the live broadcast of the Apollo 12 mission's first moonwalk.  Starting with the Apollo 15 mission, a more robust, damage-resistant camera was used on the lunar surface.  All of these cameras required signal processing back on Earth to make the frame rate and color encoding compatible with analog broadcast television standards.

Piers Sellers: Piers John Sellers OBE (11 April 1955 – 23 December 2016) was a British-American meteorologist, NASA astronaut and Director of the Earth Science Division at NASA/GSFC.  He was a veteran of three space shuttle missions.

Jean-Jacques Favier: Jean-Jacques Favier (Born April 13, 1949) is a French engineer and a former CNES astronaut who flew aboard the STS-78 NASA Space Shuttle mission.  Favier was due to fly aboard the Columbia mission in 2003, but later signed out of the mission.

Nikolay Rukavishnikov: Nikolay Nikolayevich Rukavishnikov (Russian: Никола́й Никола́евич Рукави́шников ; September 18, 1932 – October 19, 2002) was a Soviet cosmonaut who flew three space missions of the Soyuz programme: Soyuz 10, Soyuz 16, and Soyuz 33.  Two of these missions, Soyuz 10 and Soyuz 33 were intended to dock with Salyut space stations, but failed to do so.

List of Russian manned space missions: This is a list of the manned space missions conducted by the Russian Federal Space Agency since 1992.  All Russian manned space missions thus far have been carried out using the Soyuz vehicle, and all visited either Mir or the International Space Station.

Supporting paragraphs: Piers Sellers Jean-Jacques Favier
Answer: Piers John Sellers