ESA's upcoming space mission will produce solar eclipse events on demand

The European Space Agency (ESA) recently unveiled a pair of spacecraft that make up its new Proba-3 mission, planned to produce orbital solar eclipse events on demand for up to 6 hours at a time.

Due to launch in 2024, the two spacecraft - Occulter and Coronagraph - will fly approximately 150 meters apart, aligning with such precision that the former casts a shadow over the latter, blanking out the Sun to reveal the corona.

The precise formation will allow Proba-3's main ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun) instrument to yield data as if it were aboard a single rigid spacecraft, opening up a previously elusive region of study between 3 and 1.1 solar radii out from the Sun.

"The underlying idea is not new: a cylindrical Apollo capsule attempted to do the same for a Soviet Soyuz spacecraft during the Apollo-Soyuz Test Project in 1975. But the aim with Proba-3 is to produce these artificial eclipses routinely through precise formation flying, for up to six hours at a time per 19 hour 36 minute orbit," ESA explained in a recent blog post.

To achieve this level of precision, a sophisticated array of positioning technologies including satellite navigation; radio-based inter-satellite links, visible-light cameras homing in on LEDs and finally a laser beam reflected between spacecraft, will be employed.

The mission's other instrument is a radiometer measuring the Sun's total energy output, important for climate modelling.

The formation flying will be fully autonomous, taking place at the peak of each 60,000 km altitude orbit where disturbances from gravity, atmosphere, and magnetic fields are least pronounced. Outside these peak periods, the spacecraft will drift in a passive safe mode.

Next @ESA's #Proba3 spacecraft will try the same using specially-designed platforms 150 m - or 1.5⚽️fields - apartThrough precise formation flying one will cast a shadow onto the other, enabling a #SolarEclipse on demand for up to 6 hours at a time https://t.co/5QswphVz7X pic.twitter.com/1sRdSIyFGb

— ESA Technology (@ESA_Tech) April 8, 2024