The D-5 satellite project involved a pair of satellites known as Castor and Pollux; however the satellites were not twins - D-5A was a geodetic satellite while D-5B tested an accelerometer. (Although some sources say the first pair were never given the Castor and Pollux names, Le Monde for 23 May 1973 refers to Castor and Pollux). This first pair of D-5 satellites were lost when the launch vehicle failed in May 1973. Planned orbit was 300 x 1290 km x 20 deg. The third stage burned well but tumbled, and the velocity of the payload ended up 0.3 km/s too low to make orbit.
|1973 May 21||Launch by Diamant B||CSG ELD|
|Third stage guidance failed|
|Fell in Indian Ocean|