Cosmos 174

The Molniya-1Yu satellites were modified Molniya-1 satellites to test and calibrate the deep space tracking systems of the Soviet lunar program. The Molniya-1Yu satellites shared the same bus with the comsat series, but transponders were replaced by radio equipment, both operational and new, to be calibrated for tracking purposes. Two satellites, Kosmos 174 and Kosmos 260 were successfully launched.