The corner reflectors are used to reflect laser beams and are invisible to amateur observers, but the mirrors are spectacular. They are designed to reflect sunlight so the satellite can be photographed by ground stations for precise geodetic surveying measurements. The glints are probably in the third magnitude range but are visible to the naked eye only in very dark skies under good conditions.
Corner reflectors and mirrors are used to bounce laser beams, making them invisible to amateur observers; however, the mirrors stand out. They are designed to reflect sunlight for precise geodetic surveying measurements by ground stations. The glints are likely within the third magnitude range but can be seen only under ideal conditions with the naked eye.