The deployment of ESA's Mercury Planetary Orbiter (MPO) solar array is tested as part of launch preparations at Europe's Spaceport in Kourou. The solar array is not yet installed on the MPO module, which can be seen in the back left corner of the image.
The MPO is one of the three modules of the ESA-JAXA BepiColombo along with the Japanese Mercury Magnetospheric Orbiter (MMO) and the Mercury Transfer Module (MTM). The MTM will use solar electric propulsion to take the two science orbiters to the Mercury, together with gravity assist flybys at Earth, Venus and Mercury itself.
BepiColombo is Europe's first mission to Mercury, due to launch this year on a journey to the smallest and least explored terrestrial planet in the inner Solar System.