The image below, found in this answer shows four "Solar Pressure Vanes" on Mariner 4.
I've never heard of such a thing.
I can imagine that it might have been thought to help favor the spacecraft's direction more towards the Sun than away from it which might at least keeping the low gain antenna from being completely behind the spacecraft relative to Earth in the event of loss of attitude control.
But I wonder, without damping would they just induce crazy though extremely slow oscillations?
Question: What is the principle behind Mariner 4's "Solar Pressure Vanes"? In what case(s) would they be effective?
above x2: Cropped from image in COSMOS Magazine. "The Mariner 4 spacecraft. CREDIT: NASA / JPL"