The backup D-2A satellite was prepared for a mission to obtain complementary measurements from a 75 degree polar orbit. The satellite, referred to as D-2A Polaire, carried the same experiments as Tournesol plus one new one to measure the distribution of hydrogen and helium in the geocorona. Minutes after launch on 1971 Dec 5 from Kourou, the second stage of the Diamant B failed and the payload was lost.  As far as I can determine, 'Polaire' is strictly speaking an adjective applied to the D-2A name and not the name of the satellite in its own right.
|1971 Dec 5||Launch by Diamant B||CSG ELD|
|Stage 2 failed|