"This ambitious ESA mission has been many years in the making, because it is seeking to do something in space that has previously been impossible," said Damien Galano, ESA mission manager.
The Proba-3 satellites will be capable of providing sustained views of the Sun's faint corona, which is otherwise only observable during brief solar eclipses on Earth. To achieve this, the two spacecraft must keep their shadow precisely aligned, requiring autonomous formation flight with an accuracy of about one millimeter.
Galano added, "It has taken a lot of work by ESA and our industrial and academic partners to reach this point of flight readiness. There's a little sadness to finally say goodbye to these unique satellites, but we're also very excited to be progressing to the final stage before launch."
The spacecraft are scheduled to be flown to India on November 2, ahead of a new launch date set for December 4. This will be the first ESA mission launched from India since the original Proba-1 Earth-observing mission in 2001.
The planned transport process faced a delay when the spacecraft were initially not accepted by the air freight company due to their batteries being installed. This was resolved by shipping the batteries separately.
The Proba-3 satellites will be launched aboard ISRO's PSLV-XL rocket, which has the capability to lift the 550-kg combined payload into a highly elliptical orbit, extending up to 60,000 km from Earth and dropping as close as 600 km. The high-altitude orbit is crucial for minimizing Earth's gravitational influence and reducing propellant use during their precise formation flying.
The mission's industrial team includes partners from 14 ESA Member States and Canada, led by Sener in Spain for ESA. Airbus Defence and Space in Spain developed the satellite platforms, while Redwire Space in Belgium handled mission avionics, pre-launch testing, and will oversee operations after launch. GMV in Spain and Poland is responsible for formation flying systems, and Spacebel in Belgium provided software support.
Proba-3's ASPIICS instrument (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun), mounted on the Coronagraph spacecraft, will be managed by the Royal Observatory of Belgium. The Occulter spacecraft will be fitted with a 1.4-meter disk to block sunlight for the Coronagraph spacecraft during active operations.
It also carries the DARA (Davos Absolute Radiometer), which was developed by the Physical Meteorological Observatory (PMOD) in Davos, Switzerland, to measure the Sun's total energy output for climate studies. A third instrument, developed by the Catholic University of Louvain in Belgium, is the 3D Energetic Electron Spectrometer, which will measure electron energies in Earth's radiation belts to support space weather research.
Mission control for Proba-3 will be operated from ESA's ESEC (European Space Security and Education Centre) in Redu, Belgium, which is currently undergoing extensive pre-launch simulations and training.