January – Proposed launch date for Inspiration Mars, a private mission to send two people on a flyby of Mars. It’s highly unlikely the mission will ever happen, however.
February – NASA’s Juno mission, which is currently studying Jupiter, is scheduled to end. A recent issue with the spacecraft, however, has meant the mission may be extended beyond 2019.
April – The European Space Agency (ESA) will launch BepiColombo, Europe’s first mission to Mercury.
May 5 – NASA will launch its delayed InSight lander to Mars. Touchdown is expected on November 26. The unmanned probe will study the interior of the Red Planet.
May – SpaceX plans to launch its first unmanned mission to Mars, which will also be the first private Mars mission.
June – First unmanned test of Boeing's Starliner crew capsule. A manned flight will follow in August 2018.
July 31 – NASA’s Solar Probe Plus mission will launch, the first mission to fly into the Sun’s upper atmosphere, approaching within just 8.5 solar radii of the “surface”.
July – Japan’s Hayabusa 2 spacecraft will arrive at its target, the asteroid Ryugu. It launched on December 3, 2014, on its way to the asteroid, and will attempt to return a sample to Earth in December 2020.
August – NASA’s OSIRIS-REx spacecraft will arrive at the asteroid Bennu, returning to Earth in September 2023 with a sample of between 60 grams and 2 kilograms (0.1 and 4.4 pounds) – the largest sample returned to Earth since the Apollo missions.
OSIRIS-REx will fire bursts of nitrogen to loosen material from the asteroid. NASA
October – NASA’s huge new rocket, the Space Launch System (SLS), is scheduled to launch for the first time. It will send the Orion spacecraft on a three-week mission around the Moon, although rumors abound that one – or both – of the SLS or Orion may be scrapped.
October – NASA’s James Webb Space Telescope (JWST), the high-profile successor to the Hubble space telescope that has experienced numerous cost overruns and delays, will finally launch.
October - ESA will launch its Solar Orbiter (SolO), a mission that will study the Sun's heliosphere, its poles, and solar wind.
December – India will launch its next mission to the Moon, Chandrayaan-2, which will include an orbiter, lander, and rover.
TBD – Japan will launch a new Moon mission called SELENE-2, a successor to 2007’s SELENE mission. Like India’s mission, it will consist of an orbiter, lander, and rover.
TBD – China will aim to become the first nation to land a probe on the far side of the Moon with its Chang’e 4 lunar lander.