08/05/2025
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For the primary time, two spacecraft in orbit have been aligned in formation with millimetre precision and maintained their relative place for a number of hours with none management from the bottom.
The European Area Company’s Proba-3 mission has achieved its formidable aim when its two spacecraft, the Coronagraph and the Occulter, flew 150 metres aside in excellent formation, simulating a single big spacecraft.
Earlier this yr, step one of the mission was efficiently accomplished. The operations group, consisting of engineers from ESA and its intently collaborating industrial companions, got here collectively on the Company’s European Area Safety and Training Centre in Redu, Belgium.
Utilizing a set of positioning devices, they have been capable of align the 2 spacecraft in formation, and monitor them as they maintained their relative place autonomously.
Now, following extra finetuning and testing, the group has achieved the specified precision, making Proba-3 the world’s first-ever precision formation flying mission.
The mission depends on a number of progressive applied sciences, lots of that are expertise demonstrations developed by means of ESA’s Common Assist Know-how Programme (GSTP). “To do one thing that has by no means been completed earlier than, we would have liked to develop new applied sciences,” notes Esther Bastida Pertegaz, Proba-3 methods engineer.
“The formation flying is carried out when the spacecraft are greater than 50 000 km above Earth,” explains Raphael Rougeot, Proba-3 methods engineer.
“Right here, the Earth’s gravity pull is sufficiently small, in order that little or no propellant is required to take care of the formation. Then the formation is damaged and must be acquired once more over the subsequent orbit, in a repeated cycle.”
The last word aim is for the 2 spacecraft to align with the Solar in order that the 1.4-m massive disc carried by the Occulter casts a 5-cm shadow onto the optical instrument on the Coronagraph, permitting it to check the faint photo voltaic corona.
Teodor Bozhanov, formation flying system engineer, explains additional: “The initiation of this formation-flying repetitive sequence is carried out by the bottom management centre, with the operations group acquiring place info to find out the precise location of the 2 satellites in house. The mission’s thrusters are then used to carry them nearer collectively.
“All the remainder is completed autonomously. The spacecraft measure and management their relative place utilizing the Visible Based mostly System, which features a wide-angle digital camera on the Occulter monitoring a set of flashing LED lights on the Coronagraph.
“As soon as the satellites get shut sufficient to one another, a narrow-angle digital camera locking onto the identical set of lights allows a extra correct positioning.”
Raphael describes the final step wanted to shut the precision hole: “Though we have been beforehand capable of carry out formation flying utilizing solely the camera-based methods on board, we have been nonetheless lacking the specified precision.
“Two main achievements have been key to unlocking it. First, it was the calibration of the on-board laser instrument, and its integration into the complete formation flying loop.”
“This laser instrument, known as the Superb Lateral and Longitudinal Sensor (FLLS), allows relative positioning all the way down to a millimetre accuracy,” provides Jorg Versluys, Proba-3 payloads supervisor. “It consists of a laser beam fired from the Occulter spacecraft and mirrored within the Coronagraph’s retroreflector again to the Occulter, the place it’s detected.”
“The second essential achievement was efficiently utilizing the shadow place sensor,” Raphael continues. “An on-board algorithm based mostly on the measurement of sunshine depth across the coronagraph aperture ensures that the Coronagraph spacecraft stays within the shadow solid by the Occulter spacecraft.”
Esther notes: “Combining all these sensors, and due to the on-board software program managing all of the spacecraft methods and offering Navigation, Steering and Management capabilities, the formation is secure past expectations.”
Damien Galano, Proba-3 mission supervisor, concludes: “We’re speaking about millimetric accuracy in vary, and sub-millimetric within the lateral place. We are able to’t wait to see the completion of the instrument calibration and the primary processed picture of the Solar’s corona.”
The Proba-3 mission is led by ESA and put collectively by a consortium managed by Spain’s Sener, with participation of greater than 29 firms from 14 international locations and with key contributions from GMV and Airbus Defence and Space in Spain and Redwire Space and Spacebel in Belgium.
The coronagraph instrument comes from Belgium’s Centre Spatial de Liège (CSL) and the science information can be processed by the Royal Observatory of Belgium. The mission was launched on 5 December 2024 on a PSLV-XL launcher from Satish Dhawan Area Centre in Sriharikota, India.
