COSMOS 1688 (also known as Kosmos-1688) is a radar calibration satellite launched on October 2, 1985, from the Kymry Space Center's LC107/1 launch pad using the Kosmos 11K65M launch vehicle. The spacecraft, manufactured by YUZH and owned by PVO, has dimensions of 2.5 meters in length and a diameter of 1.8 meters, with a span of 23 meters. It has a dry mass of 925 kilograms and a launch mass of 1045 kilograms. The satellite is equipped with eight deployable fixed solar arrays and batteries for power generation. Its payload includes the Taifun-2V (08) system, and it features a cylindrical shape augmented by antennas. The spacecraft's radar cross-section is measured at 39.9031 square meters.