Venera 11:
Venera 11 was one of two identical probes (the other being Venera 12) that followed up on the highly successful Soviet missions to Venus in 1975.
Veneras 11 and 12 differed from their predecessors principally in the fact each carried a flyby bus/lander combination instead of the previous orbiter/lander combination. Engineers reverted to the flyby combination partly because of the weight limitations of the 1978 launch window, but also because flyby probes afforded better transmission time for landers. Several of the scientific instruments were also modified and new ones added.
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