This Day In Space History: August 18

1686

https://www.revolvy.com/topic/Neith%20(hypothetical%20moon)&uid=1575

Giovanni Cassini (1625-1712) sights what he believes is a natural satellite of Venus. The hypothetical moon is called Neith.

1868

https://www.wired.com/2009/08/dayintech_0818/
In his observation of the spectral lines of a solar eclipse in Guntur, India, French astronomer Pierre Janssen (1824-1907) discovers helium, recognizing that a wavelength didn't match that of any known element.

1960

Discoverer XIV, "the first successful low resolution photo surveillance spacecraft" (nasa.gov) is launched from Vandenberg Air Force Base. learn more here: https://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1960-010A

1976

http://www.onthisday.com/events/august/18

The Soviet spacecraft Luna 24 lands on the moon's surface, ten days after its launch.

1993

http://www.yearinspace.com/the-week-in-space

The first flight of the Delta Clipper (DC-X), a reusable spacecraft.

For a complete list of today’s Space History, see  http://www.astronautix.com/a/august18.html