Fig. 1: Identification concepts for satellites.
From: Space object identification via polarimetric satellite laser ranging
a Coded light signals (e.g., from a light-emitting diode, LED) are emitted at the satellite and detected on Earth with an optical telescope. An example for this technology is the Extremely Low Resource Optical Identifier (ELROI). b A radio signal carrying an ID is detected by a radio telescope. An example for this technology is the CubeSat Identification Tag (CUBIT). c In satellite laser ranging (SLR) emitted laser light (Tx) is retroreflected from one or more retroreflectors (red spots on the satellite) and the signal Rx (the red dots represent detected photons) is detected at the SLR ground station. d Modulated retroreflectors use electro-optical shutters to modulate the retroreflected intensity of a laser beam. This can be used for laser communication or provide an ID of the satellite.
