The CSL (Centre Spatial de Liège) is a research center of the University of LIEGE. The activities of CSL are international: collaborations with ESA and NASA, with most of the European space industries and laboratories and with many large US laboratories. Through its space activities, CSL has accumulated high-level instrumentation which is regularly set to the disposal of the industry.


The Coarse Lateral Sensor (CLS) developed by CSL is based on a camera (CMOS detector), a telecentric lens, a fiber-coupled laser-diode bar, and a corner cube. The fiber-coupled laser-diode bar emits a diverging beam, from the coronagraph satellite. A corner cube located on the occulter satellite sends the light back. This light is captured by the telecentric lens and camera, located on the other satellite. A lateral shift of the PROBA-3 Occulter S/C is seen on the camera as an image displacement. Pseudo real time centroidisation algorithms, allow tracking the image position and feed the on-board computer with this information, allowing position stabilization.

DELTATEC has developed the EM (engineering model) of the Optical Head Unit (OHU) of the CLS and is now in charge of the QM (Qualification Model) and FM (Flight Model).


Additionally to the standard space constraints already met in the SWAP project, CLS project presented two challenges, successfully overcome by DELTATEC.

The first one was to deal with a space qualified mechanical design. Space mechanical design needs particular attention in order to fulfill the space environment requirements (vibrations, thermos-elastic constraints in a huge temperature range…).

The second one was the elaboration and implementation in the RTAX FPGA of the centroid algorithm. This Algorithm has to deal with the sun that could be in the field of view of the system.


DELTATEC developed the CLS Optical Head Unit (OHU). Based on the Proba 2 SWAP development, the OHU is based on one HAS CMOS APS image sensor from Cypress.

The proximity detector electronics provides clock drivers, sensor control, signal conditioning and Analog to Digital Conversion (ADC).

The processing, for centroid computation, is based on a Microsemi RTAX FPGA.

Interface with the higher level unit is provided by a bi-directional RS422 serial link. This link allows CLS control (TM/TC) and centroid coordinates acquisition.

Additionally a high speed unidirectional serial link for EGSE image read-out and data read-out.

DELTATEC also developed the Electrical Ground Support Equipment (EGSE) for the CLS.