The best that can be said about Discoverer 17 (aka Corona 9012) is that it wasn’t a complete failure. It was launched on November 12th 1960, from Vandenburg Air Force Base in California. Low Earth orbit was attained, and the plan was to shoot a roll of high resolution black and white 70mm film showing how quickly the Soviet Union were developing their long range ballistic missile capability, then return it to Earth aboard the “satellite recovery vehicle” (SRV). Unfortunately, the mission suffered from premature separation of the SRV, resulting in only a couple of feet of unused film being returned to Earth. The rest of Discoverer 17 remained in orbit until 29th December, at which point it was burnt up on reentry.
There was also a biological research aspect to Discoverer 17 (the cover story), involving a study of the effect on human beings of leaving the atmosphere (at that time no-one had yet got into space). This was the part of the mission that didn’t fail, as insight was gained on the effect of massive doses of radiation on human tissue. (And yet they still found volunteers to go up there.)
1862 ⇒ Discovery of asteroid 77 Frigga by Christian Heinrich Friedrich Peters. This M-type main belt asteroid is named after the Norse goddess Frigg, wife of Odin.
1879 ⇒ Discovery by Johann Palisa of the F-type asteroid 210 Isabella. F-types are a sub-division of the carbocaceous “C” group. They are similar to B-types, but are suspected to lack hydrated minerals. There’s a big day coming soon(-ish) for B-type asteroids, as we are fast approaching the arrival of NASA’s OSIRIS-Rex mission at B-type 101955 Bennu, in August 2018.
1885 ⇒ Discovery of asteroid 253 Mathilde by Johann Palisa. It is a dark main belt asteroid of about 50km wide, named after the wife of the director of the Paris Observatory, Maurice Loewy.
Mathilde is a rare beast among early asteroid discoveries, as we actually have close-up photographs of her, taken by the passing NASA mission, NEAR Shoemaker, which was on its way to rendezvous with the near-Earth asteroid, 433 Eros.
2015 ⇒ Two years ago today ESA successfully landed (or bounced) their Philae lander on comet 67P/Churyumov–Gerasimenko, having been launched from the Rosetta spacecraft some hours earlier.
This was a big day for ESA, and spaceflight in general, as it was the first time a probe had landed on a comet.