7P/Pons–Winnecke
7P/Pons–Winnecke (also known as Comet Pons–Winnecke) is a periodic Jupiter-family comet with a six-year orbit. Early calculations for the 1921 apparition suggested that the orbit of the comet might collide with Earth in June, but observations on 10 April ruled out an impact. It made a very close approach to Earth in June 1927. The outward migration of perihelion created impressive meteor showers in 1916, 1921 and 1927. The next perihelion passage is 27 May 2021 when the comet will have a solar elongation of 107 degrees at approximately apparent magnitude 11 . It passed from Earth on 12 June 2021. The last perihelion was on 30 January 2015, and at the 2015 perihelion it had a solar elongation of 24 degrees. Jean Louis Pons (Marseille) originally discovered the comet on 12 June 1819, it was later rediscovered by Friedrich August Theodor Winnecke (Bonn) on 9 March 1858. It is the parent body of the June Bootids of late June. 7P has an orbital period of 6.37 years. It has a perihelion of 1.3 AU and an aphelion of 5.6 AU (past the orbit of Jupiter). It passed within of Earth in June  1927, and in 1939; but it will not come as close in the 21st century. A close approach to Jupiter in July 2037 will drop perihelion back to 0.982 AU. The comet nucleus is estimated at about 5.2 km in diameter. Proposed exploration. The Jet Propulsion Laboratory proposed a flyby of the comet with a flight spare of Mariner 4 with the closest approach taking place in 1969. The probe was instead used for a Venus flyby as Mariner 5.