China will launch the Chang’e-4 relay satellite to the Moon, intended to be the orbital component of a planned lunar lander on the far side of the Moon at the end of the year.
Japan’s Hayabusa-2 spacecraft will reach its target asteroid Ryugu. The plan is to return a sample of the asteroid to Earth in December 2020.
NASA’s Parker Solar Probe will launch on July 31, and will study the Sun by getting closer than any spacecraft has before, just 17 times further than the width of the Sun itself. It will also become the fastest spacecraft on record as it “touches the Sun”, reaching a speed of 200 kilometers (124 miles) per second.
NASA’s Juno mission at Jupiter is expected to end by plunging into the atmosphere of the gas giant, although there is a chance the mission could be extended.
Boeing will perform an uncrewed test of its CST-100 Starliner spacecraft, with plans to then launch humans in November at the earliest.
SpaceX says it will perform a crewed flight test of the Crew Dragon. If this goes ahead, it will be the first time astronauts have launched from US soil since 2011. (Update November 11: Pushed back to December 2018 at the earliest)
NASA’s Osiris-REx spacecraft will reach its target, the asteroid Bennu, from which it will return a sample to Earth in 2023.
The joint European and Japanese BepiColombo mission will launch to Mercury. The mission comprises two orbiters, but it will not arrive into orbit around Mercury until December 2025, owing to the complexities of orbiting a body so close to the Sun.
On December 20, we’re finally expecting the launch of one of the final modules of the ISS, the Russian-built Nauka module, which has been delayed since 2007.
And this final one is kind of cheating but… On December 31, it will be one day before the New Horizons spacecraft arrives at its next target, the Kuiper Belt Object called MU69. Not a bad way to ring in 2019.