CHAMP
RetroReflector Array (RRA) Characteristics:

Courtesy of GFZ
The laser retro reflector is a simple passive payload instrument consisting of four prisms to reflect short laser pulses back to the transmitting ground station. This enables the measurement of the direct two-way range between ground station and satellite with an accuracy of 1 to 2 cm. More information on laser ranging analysis for CHAMP can be found in the paper 'The Retro-Reflector for the CHAMP Satellite: Final Design and Realization' presented in 1998 at the International Laser Ranging Workshop in Deggendorf, Germany.