Proba-3, consisting of two spacecraft operating as a single unit, will use a unique design to block the Sun's glare, enabling continuous observation of the corona. This mission will expand our understanding of solar dynamics, including the forces driving coronal mass ejections (CMEs) and the solar wind.

The corona's mysteries began unraveling with Bernard Lyot's 1931 coronagraph, a telescope using an occulting disc to block the Sun. However, diffraction, a phenomenon where light waves bend around edges, limits the effectiveness of ground-based instruments. ESA's Proba-3 overcomes this by separating the Sun-blocking disc from the observing telescope, allowing for clearer views.

"This might sound simple, but it's rendered much harder by the peculiar fact that light acts as both particles and waves," explained Damien Galano, ESA's Proba-3 mission manager. "This diffraction must be minimized to prevent unwanted sunlight from reaching the instrument."

By flying the occulter and telescope on separate spacecraft, spaced 150 meters apart, Proba-3 achieves an exceptional level of clarity. Principal Investigator Andrei Zhukov noted, "We'll observe much closer to the Sun's edge than previously possible, filling gaps in our understanding of the corona."

This groundbreaking approach builds on earlier experiments, such as the Apollo-Soyuz mission, which attempted similar observations but faced challenges from spacecraft-generated glare. Two decades of development led to the refined design adopted by ESA, which balances technological capability with practical limitations like precision tracking and fuel efficiency.

Proba-3's ASPIICS instrument, developed with input from European teams, incorporates innovations like a dual-disc system to counteract stray light. The primary 1.4-meter occulting disc, crafted from carbon fiber reinforced plastic by Airbus in Spain, works in tandem with a smaller central disc to block diffracted light waves.

The instrument, hosted on the Coronagraph spacecraft, and the accompanying Occulter spacecraft form a virtual telescope stretching 150 meters. This configuration allows observation of the corona from just 1.1 solar radii, a significant improvement over conventional coronagraphs.

During its operational phase, Proba-3 will deliver six-hour observations twice a week. "Instead of relying on fleeting solar eclipses, we'll have extended and detailed views of the corona," said Zhukov. Rapid imaging at intervals as short as 30 seconds will capture the evolution of solar events with unprecedented detail.

Mission scientist Joe Zender added, "The closer we get to launch, the more I realize the excitement of what we're achieving, including coordinated observations with other solar missions."

After a four-month commissioning period, Proba-3 will enable scientists to monitor the solar corona and the phenomena within it, significantly advancing our understanding of the Sun's influence on the solar system.

Related Links
Proba-3 at ESA
Solar Science News at SpaceDaily