Dec 092015
Images of the Mariner 4 probe, which flew past Mars on July 15, 1965, the first time a spacecraft successfully explored the planet. Note the “Solar pressure Vanes.” These were, as may seem obvious from the photos, very lightweight reflectors. While solar photon pressure was not enough to turn the Mariner 4 into any sort of meaningful solar sail, it was enough to actually adjust the attitude of the spacecraft.
