Proba-3 Mission Prepares for Precision Formation Flying with Laser Metrology Tests

Proba-3 Mission Prepares for Precision Formation Flying with Laser Metrology Tests
by Robert Schreiber
Kruibeke, Belgium (SPX) Mar 01, 2024

In a significant step toward realizing the European Space Agency's (ESA) ambitious Proba-3 mission, a crucial laser-based test campaign is currently underway at Redwire Space's facilities in Kruibeke, Belgium.

This mission, poised to revolutionize our approach to observing the sun, involves two satellites, namely the 'Occulter' and the 'Coronagraph,' which will maintain a precise formation in space, effectively creating an artificial solar eclipse. This will allow for unprecedented, sustained observation of the sun's corona for up to six hours during each 19.5-hour orbit.

Scheduled for launch later this year aboard a PSLV-XL launcher from India, the Proba-3 mission's primary objective is to block out the sun's luminous face with the Occulter spacecraft, casting a shadow on the Coronagraph spacecraft. This setup will enable scientists to study the sun's corona in detail, a feat that has been challenging to achieve through other means. The key to this mission's success lies in the ability of the two satellites to maintain their relative positions with millimetre precision, despite being 150 meters apart in space.

Achieving such precision requires an advanced suite of sensors, including intersatellite radio links, GNSS, visual imaging, and most critically, a laser metrology system. This system is designed to measure the distance and attitude between the two spacecraft with unprecedented accuracy. The Occulter spacecraft will emit a laser towards a corner cube retroreflector on the Coronagraph spacecraft, enabling precise tracking of their relative positions.

Damien Galano, Proba-3's mission manager, elaborated on the meticulous calibration process for the laser metrology system. "Within the expansive 60-meter long cleanroom at Redwire, we tested the Coronagraph's laser by reflecting it off a retroreflector. The resulting positioning measurements were then validated against an absolute 'ground truth' provided by a separate laser tracking system," he explained.

The construction of the Proba-3 mission is a collaborative effort led by Spain's Sener, with contributions from over 29 companies across 14 countries. Notably, the Proba-3 platforms were designed by Airbus Defence and Space in Spain, with satellite integration carried out by Redwire in Belgium. The formation flying subsystem is the responsibility of GMV in Spain, while the main coronagraph instrument is a product of Belgium's Centre Spatial de Liege (CSL).