PROBA-3 is a dual-probe technological demonstration mission by the European Space Agency devoted to high-precision formation flying to achieve scientific coronagraphy.

[5] The twin spacecraft reached the launch site, Satish Dhawan Space Center on the Eastern coast of India on 3 November 2024.

[3][11][12] ESA said that by flying in tight formation about 150 metres apart, the Occulter will precisely cast its shadow onto the Coronagraph’s telescope, blocking the Sun’s direct light.

[13] Along the apogee arc, when the gravity gradient is significantly smaller, the two spacecraft will autonomously acquire a formation configuration, such that the CSC remains at a fixed position in the shadow cast by the OSC.

Besides formation flying for coronagraphy, some demonstration manoeuvers (retargeting and resizing) will be attempted during the apogee phase of the orbit, as well as a space rendezvous experiment.

Along the perigee phase of the orbit, the two spacecraft acquire GNSS data to derive a precise estimation of the relative position and velocity, which is propagated for a few hours up to the reacquisition of the metrology before the next apogee arc.

Scientists hope that PROBA-3’s unique vantage point will provide new insights into the origins of coronal mass ejections (CMEs) – eruptions of solar material that can disrupt satellites and power grids on Earth.

The mission will also measure total solar irradiance, tracking changes in the Sun’s energy output that may influence Earth’s climate.

[15] It is expected that the data from ASPIICS will fill the gap in term of field of view between EUV imagers and externally occulted coronagraphs, when the latter are monolithic instruments that don't benefit from the longer distance enabled by formation flying.

Members of the team plan to test flight hardware during April's total solar eclipse over North America, gaining valuable experience for interpreting PROBA-3’s future results.