Influence of reflecting surface characteristics on a laser rangefinder

The laser rangefinder can enable the distance of remote objects, such as satellites, to be determined with an accuracy of 1.5 m up to a distance of 3000 km. This performance level accrues from three main factors: (i) the directivity of the laser light, which allows the emitted power to be concentrated in a very narrow cone; (ii) the high detection capability of up-to-date photomultipliers, which can generate a signal even in response to a mere hundred or so photons received; (iii) the directive reflexion properties of the retroreflective systems located on the object observed. The present paper investigates this last factor. It outlines the reflective photometric characteristics of various scattering and reflecting surfaces for comparison with those of retroreflectors, and describes several retroreflective systems. The comparison is made with a practical example, which corresponds to a rangefinder used for satellites. It is thereby demonstrated that a single 2 cm diameter retroreflector ensures a range 29 times that obtained on a 1 m2 diffusing surface and 6.7 times that achieved on a 1 m2 surface covered with glass balls.