DS-P1-Yu was a series of Soviet satellites developed by the Yuzhnoye Design Office of Ukraine, for use in calibrating the Dnestr space surveillance and early-warning radar system. Between 1964 and 1976, a total of 79 satellites were launched on Kosmos-2I 63S1 launchers, with seven failing to reach orbit. The dodecahedral satellites had a mass of 193–240 kilograms (425–529 lb) and an operational lifetime of 60 days. They were covered in solar panels and a metallic mesh transparent to visible spectrum light and opaque to radio frequencies.