Question: Who was the French professor that the Robert brothers built the world's first hydrogen balloon for?
Context: Langworthy Historic District is a nationally recognized historic district located in Dubuque, Iowa, United States.  It was listed on the National Register of Historic Places in 2004.  At the time of its nomination it consisted of 110 resources, which included 94 contributing buildings, five contributing structures, nine non-contributing buildings, and two non-contributing structures.  This residential area was developed from the end of the American Civil War to the beginning of World War I.  Most of the houses were built between 1890 and 1910, with four large houses pre-dating the Civil War.  For the most part, the houses here are larger in scale and include examples of Victorian and the various revival and American Movement styles from the late 19th and 20th centuries.  The district is completely residential with no commercial or institutional buildings, and with only one multi-family house, a duplex.  Two houses were individually listed on the National Register: Langworthy House, an Octagon house from 1855, and the Garland House (1907).  The district derives its name from the Langworthy family who were early settlers in Dubuque and played a prominent role in the development of the local lead mining industry and the city itself.  Three of the brothers built houses here. Alec Wilkinson (b. 1952 - ) is a writer who has been on the staff of "The New Yorker" since 1980.  According to "The Philadelphia Inquirer" he is among the "first rank of" contemporary American (20th and early 21st century) "literary journalists...(reminiscent) of Naipaul, Norman Mailer and Agee."  He is the author of ten books: "Midnights," (1982), "Moonshine," (1985), "Big Sugar," (1989), "The Riverkeeper," (1981), "A Violent Act, (1993), "My Mentor," (2002), "Mr. Apology," (2003), "The Happiest Man in the World," (2007), the latter about Poppa Neutrino, the only man to cross the Atlantic in a raft made of trash, and "The Protest Singer: An Intimate Portrait of Pete Seeger," (2009).  His most recent book is "The Ice Balloon," (2012), the account of the Swedish visionary aeronaut S.A. Andree's attempt, in 1897, to discover the North Pole by flying to it in a hydrogen balloon.  Before Wilkinson was a writer, he was a policeman in Wellfleet, Massachusetts, on Cape Cod, which is the subject of "Midnights," and before that he was a rock and roll musician, playing in a number of bands, including one in Berkeley, California with Tony Garnier, Bob Dylan's longtime bass player and bandleader.  Wilkinson began writing when he was twenty-four, showing work to William Maxwell, his father's friend, who in addition to being a novelist and short-story writer, had for forty years been an editor of fiction at The New Yorker.  They worked together closely for years.  Maxwell died in July 2000.  "My Mentor" describes their friendship.  Wilkinson's honors include a Lyndhurst Prize, a Robert F. Kennedy Book Award and a Guggenheim fellowship.  He is married, has a son, and lives in New York City.  He is also the brother of Leland Wilkinson. Testu-Brissy made his first balloon ascent in 1785, and the first night ascent on 18 June 1786 in a hydrogen balloon.  He made the world's first electrical observations on 18 June 1786 as he ascended into thunderclouds, and said that he drew remarkable discharges from the clouds by means of an iron rod, carried in the car. S. A. Andrée's Arctic balloon expedition of 1897 was an effort to reach the North Pole in which all three expedition members perished.  S. A. Andrée (1854–97), the first Swedish balloonist, proposed a voyage by hydrogen balloon from Svalbard to either Russia or Canada, which was to pass, with luck, straight over the North Pole on the way.  The scheme was received with patriotic enthusiasm in Sweden, a northern nation that had fallen behind in the race for the North Pole. Jacques Alexandre César Charles (November 12, 1746 – April 7, 1823) was a French inventor, scientist, mathematician, and balloonist. A fire balloon (風船爆弾 , fūsen bakudan , lit.  "balloon bomb") , or Fu-Go (ふ号[兵器] , fugō [heiki] , lit.  "Code Fu [Weapon]") , was a weapon launched by Japan during World War II.  A hydrogen balloon with a load varying from a 15 kg antipersonnel bomb to one 12 kg incendiary bomb and four 5 kg incendiary devices attached, it was designed as a cheap weapon intended to make use of the jet stream over the Pacific Ocean and drop bombs on American and Canadian cities, forests, and farmland. L'Intrépide ("The Intrepid") was a hydrogen balloon of the "Compagnie d'Aérostiers" (French Aerostatic Corps) and is the oldest preserved aircraft in Europe. Jean-François Pilâtre de Rozier (30 March 1754 – 15 June 1785) was a French chemistry and physics teacher, and one of the first pioneers of aviation.  He and the Marquis d'Arlandes made the first manned free balloon flight on 21 November 1783, in a Montgolfier balloon.  He later died when his balloon crashed near Wimereux in the Pas-de-Calais during an attempt to fly across the English Channel.  He and his companion, Pierre Romain, thus became the first known fatalities in an air crash.  He also risked himself while researching the flammability of hydrogen: in "A Short History of Nearly Everything", Bill Bryson writes "In France, a chemist named Pilatre de Rozier tested the flammability of hydrogen by gulping a mouthful and blowing across an open flame, proving at a stroke that hydrogen is indeed explosively combustible and that eyebrows are not necessarily a permanent feature of one’s face." Energy Observer is a hydrogen vessel launched in April 2017.  Developed in collaboration with engineers from the CEA- the boat will test and prove the efficiency of a full production chain that relies on the coupling of different renewable energies.  Energy Observer will be the "first hydrogen vessel around the world".  Following its launch, scheduled for winter 2017, the boat will leave in the Spring for a world tour lasting 6 years in order to optimize its technologies and lead an expedition that will serve durable solutions for energy transition. Les Frères Robert were two French brothers.  Anne-Jean Robert (1758–1820) and Nicolas-Louis Robert (1760–1820) were the engineers who built the world's first hydrogen balloon for professor Jacques Charles; which flew from central Paris on August 27, 1783.  They went on to build the world's first manned hydrogen balloon, and on 1 December 1783 Nicolas-Louis accompanied Jacques Charles on a 2-hour, 5-minute flight.  Their barometer and thermometer made it the first balloon flight to provide meteorological measurements of the atmosphere above the Earth's surface.
Answer: Jacques Alexandre César Charles