Europe’s two eclipse-creating spacecraft are set to launch from India on Wednesday, beginning a mission that will require precision spaceflight down to the millimeter.The European Space Agency Proba-3 mission will launch from the Satish Dhawan Space Centre in Sriharikota, India, at 4:38 p.m. local time. Proba, which is Latin for “let’s try,” is another mission from an ESA program dedicated to precision satellite flying. According to the ESA, achieving precise formation spaceflight will open “a whole new era for science and applications” on a much larger scale. Probe-3 consists of two spacecraft that will work in tandem as one spacecraft casts a controlled shadow, creating an eclipse for the other spacecraft. An eclipse is the only time you can observe the ghostly corona or the Sun’s outer atmosphere.While eclipses of the Sun on Earth happen about every 18 months, Proba-3 will be able to create one on demand. The Coronagraph spacecraft and the other Occulter spacecraft will fly in formation using the Coronagraph to block out the solar disk and obtain views of the corona.According to the ESA, the spacecraft will fly 150 meters apart with precision down to the thickness of a fingernail. The pair must maintain this dance for every six hours within a 19.5-hour orbit.Proba-3 will also test sensors and algorithms for a rendezvous in an elliptical orbit, which could be used for the upcoming Mars sample retrieval mission with NASA.After liftoff, the Proba-3 spacecraft are expected to separate from the rocket 18 minutes later and establish contact with ground stations in Europe about 15 minutes later.