Fifty years ago today — September 28, 1962* — the Alouette 1 satellite launched from Vandenberg AFB on a Thor Agena rocket.
(Alouette 1 before launch. NASA image.)
Alouette 1 was a Canadian-built spacecraft designed to make scientific observations of the ionosphere, that region above the stratosphere where the atmosphere is ionized by the sun. Despite attitude control issues that caused the spin-stabilized satellite to slow down more than expected, it continued to operate until September 1972.
The Wikipedia entry on Alouette 1 notes that Alouette 1 is sometimes the subject of confusion regarding its place in space history. To be clear, it was not the third satellite placed in orbit, nor was it the first satellite to be owned by a country other than the U.S. and U.S.S.R — instead, it was the first satellite to be built by a third country, making Canada the third nation to have a home-built spacecraft in orbit.
*Sometimes listed as the 29th, using UTC.