The double-satellite Proba-3 is the most ambitious member yet of ESA’s Proba family of experimental missions. Two spacecraft will fly together as one, maintaining precise formation down to a single millimeter.

One will block out the fiery disk of the sun for the other, to enable prolonged observations of the sun’s surrounding atmosphere, or corona, the source of the solar wind and space weather.

Usually, the corona can only be glimpsed for a few minutes during terrestrial total solar eclipses. Proba-3 aims to reproduce such eclipses for up to six hours at a time, in a highly elliptical orbit taking it more than 60,000 km from Earth.

The two spacecraft are being launched together by India’s PSLV-XL launcher from the Satish Dhawan Space Center. Follow the mission’s deployment and commissioning, up to its first glimpse of the corona, in this overview video.