Daily Extra :
Astronomy & Space Word of The Day
synchronous orbit radius: The orbital radius at which the satellite's orbital period is equal to the rotational period of the planet. A synchronous satellite with an orbital inclination of zero (same plane as the planet's equator) stays fixed in the sky from the perspective of an observer on the planet's surface (such orbits are commonly used for communications satellites).
Today in History:
1969: Apollo 10, USA Lunar Manned Orbiter, (May 18-26, 1969) Crew: Thomas Stafford, Eugene A. Cernan, John W. Young. Manned lunar fly-around and Earth return. Stafford and Cernan tested the Lunar Module, separating it from the Command and Service Module and descended to within 50,000 feet of the lunar surface. The astronauts acquired a large number of excellent 70-mm photographs.