That's No Moon

(Image from European Space Agency.)

From the European Space Agency today, "Proba-3's first artificial solar eclipse":

This March, Proba-3 achieved what no other mission has before – its two spacecraft, the Coronagraph and the Occulter, flew 150 metres apart in perfect formation for several hours without any control from the ground.

While aligned, the pair maintain their relative position down to a single millimetre – an extraordinary feat enabled by a set of innovative navigation and positioning technologies.

Demonstrating the degree of precision achieved, the two spacecraft use their formation flying time to create artificial total solar eclipses in orbit – they align with the Sun so that the 1.4 m large disc carried by the Occulter spacecraft covers the bright disc of the Sun for the Coronagraph spacecraft, casting a shadow of 8 cm across onto its optical instrument, ASPIICS.

And here's the actual corona, with the full occulting:

(Also from the European Space Agency.)