Explorer 3 was launched on March 26th 1958 from Cape Canaveral, using a Juno I four stage launcher, the same rocket that had been used to launch (successfully) Explorer 1 and (less than successfully) Explorer 2.
Explorer 3 looked almost exactly like Explorer 1, hence the non-committal title of the above photograph, and had the same task, to explore the Earth’s radiation belts. Those whip-like things sticking out from the body are transmitting antennae, kept extended by the rotation of the satellite.
Asteroid 561 Ingwelde discovered by Max Wolf in 1905. The prevailing view seems to be that Ingwelde was named after the opera by Max von Schillings. I’m inclined to agree, as the opera had been doing the rounds in the years leading up to 1905. Following its premiere in Karlsruhe (1894) it had been revived in Munich in 1896, directed by no less a person than Richard Strauss (albeit for only three performances).