Laser Retro-Reflector (LRR)
Precise orbit determination relies on the data from the GPS receivers providing full global coverage of orbit data. The alternative method of Satellite Laser Ranging (SLR) is used as a supporting and independent means for orbit determination. Its limitation is the rather poor global and temporal coverage, but the SLR data is free from ambiguities and directly related to the terrestrial reference frame.
Each of the Swarm satellites is equipped with a Laser Retro-Reflector (LRR) of novel design (More Information) for external calibration and validation of the onboard GPS receiver. A basic requirement for LRR is to enable the worldwide SLR station network to track the satellite with high accuracy and with a sufficiently high link budget under both night and daytime ranging conditions.