Europe says farewell to eclipse-making Proba-3

“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,” explains ESA mission manager Damien Galano.  

“Once in orbit, Proba-3’s two satellites will enable sustained views of the Sun’s faint surrounding atmosphere, or corona, that has previously only been visible for a few brief moments during terrestrial solar eclipses. To achieve this the shadow being cast between the spacecraft must remain in precise position, which means they must fly autonomously in formation to an accuracy of a single millimetre – about the thickness of an average fingernail. 

“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.” 

Proba-3 is now due to be flown to India on Saturday 2 November, for a new launch date of 4 December.  

This is the first time that an ESA mission is being launched from India since the original Proba-1 Earth-observing mission in 2001, and the planned transport process was hit by a delay. The spacecraft were initially not accepted by the air freight company since their batteries were already installed aboard them. This was solved by removing the batteries to be shipped in a separate box. 

The two Proba-3 spacecraft will be launched together by the PSLV-XL launcher of the Indian Space Research Organisation, ISRO, which possesses the necessary power at a workable cost to place the 550-kg combined pair into their highly elliptical (or elongated) orbit which will ascend to 60 000 km away from Earth before coming as low as just 600 km. 

This high orbit is required because the pair will perform their active formation flying for a planned six hours at a time around their maximum altitude, where Earth’s gravitational pull will be diminished, as will the amount of propellant needed to fine-tune their positions. 

An industrial grouping from 14 ESA Member States including Canada contributed to the mission, led for ESA by Sener in Spain, with Airbus Defence and Space in Spain contributing the satellite platforms and Redwire Space in Belgium responsible for the mission avionics, pre-launch testing and post-launch operations.  

GMV in Spain and Poland – focused on formation flying, relative satnav and flight dynamics – plus software-providing Spacebel in Belgium complete the core industrial team.

Proba-3’s main corona-observing ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun) instrument, hosted on the Coronagraph spacecraft, will be overseen by the Royal Observatory of Belgium. 

The mission’s Occulter spacecraft, fitted with a 1.4-m disk, is tasked with blocking out of the Sun for the Coronagraph spacecraft during active formation flying. It carries its own instrument on the Sunward side, DARA (Davos Absolute Radiometer) to measure the Sun’s total energy output for climate studies, developed by the Physical Meteorological Observatory. PMOD, in Davos, Switzerland. 

A third instrument led by Belgium's Catholic University of Louvain, the 3D Energetic Electron Spectrometer, will measure prevailing angle-resolved electron spectra energies in Earth’s surrounding radiation belts, providing valuable data for space weather modelling. 

Mission control for Proba-3 will take place from ESA’s ESEC European Space Security and Education Centre, in Redu, Belgium, which is currently undertaking an extensive pre-launch simulation and training campaign. 

Find out more about the Proba-3 industrial consortium here.