... EXPERIMENTS AND RESEARCHES . ... SPQR EXPERIMENT . ... SPQR unit is a retroreflector for a laser radiation of an optical range coming through the window. ... Testing of the ISS imaging system using special ground-based optics and image processing aids to detect possible damages on the external surface of the Station. ... Determination of a reference point of the ISS orbit using cube cone reflector and ground station laser with simultaneous reception of ISS image on the ground using a telescope. ...