Ground crews at the Guiana Space Center in South America. BepiColombo spacecraft, a tandem mission with European and Japanese science orbiters bound for Mercury, for launch aboard an Ariane 5 rocket.
Liftoff is scheduled for 0145 GMT on Oct. 20 (9:45 p.m. EDT on Oct. 19) from Kourou, French Guiana.
The BepiColombo spacecraft stands 21 feet (6.4 meters) tall at launch and weighs 8,997 pounds (4,081 kilograms) fully fueled with hydrazine and xenon propellants for the 7.2-year journey to Mercury.
Workers at the spaceport in French Guiana have spent the last few months reading the BepiColombo spacecraft for launch. Key steps included filling the spacecraft with propellant, and stacking the major parts of the vehicle for the planet system.
BepiColombo's European-built Mercury Planetary Orbiter carries 11 instruments, a suite comprising a high-resolution mapping camera, a laser altimeter, an accelerometer, and a set of spectrometers on a downward-facing science deck that will remain pointed to the planet over each orbit .
The Japanese-made Mercury Magnetospheric Orbiter's Five Science Scientists will study the plasma environment around Mercury's attempt to image the planet's sodium-rich atmosphere, and measure Mercury's magnetic field.
The spacecraft also includes the Mercury Transfer Module, a section with a steerable plasma engines and solar arrays designed to steer BepiColombo through the inner solar system through a series of gravity assist encounters with Earth, Venus and Mercury before finally arriving in the orbit of the planet innermost in December 2025.
The BepiColombo will be part of the Mercury, with the European and Japanese orbiters heading to different orbits. The Mercury Transfer Module will be jettisoned along with a sunshield that will keep the Japanese part of the world at the crossroads of Earth to Mercury.
BepiColombo will become the second mission to orbit Mercury after NASA 's MESSENGER spacecraft, which explored the planet from 2011 through 2015.
The photos below show the BepiColombo spacecraft's launch preparations in French Guiana after a series of Antonov cargo flights delivered the major parts of the mission to the launch base from Europe.