The following images were photographed from aboard the Columbia
Space Shuttle in 1986 and appear to show a black triangle high above the Earth's atmosphere and relatively close to the Shuttle.
This first one is archived here
in NASA's online database, described as 'space debris' and as having been taken on the 12th of January 1986 while the object was over the Atlantic Ocean.
Mission STS-61-C was the twenty-fourth mission of NASA's Space Shuttle program, the seventh mission of Space Shuttle Columbia
, and the last successful Space Shuttle flight before the Challenger
disaster, which occurred only 10 days after Columbia
's return (Wikipedia
, of course, later disintegrated upon re-entry in 2003.
'Space debris' may be many things, but sharply defined triangles probably isn't one of them...