The Space Shuttle was a partially reusable low Earth orbital spacecraft system that was operated from 1981 to 2011 by the U. S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program name was Space Transportation System (STS), taken from a 1969 plan for a system of reusable spacecraft of which it was the only item funded for development. The first of four orbital test flights occurred in 1981, leading to operational flights beginning in 1982. In addition to the prototype whose completion was cancelled, five complete Shuttle systems were built and used on a total of 135 missions from 1981 to 2011, launched from the Kennedy Space Center (KSC) in Florida. Operational missions launched numerous satellites, interplanetary probes, and the Hubble Space Telescope (HST); conducted science experiments in orbit; and participated in construction and servicing of the International Space Station. The Shuttle fleet’s total mission time was 1322 days, 19 hours, 21 minutes and 23 seconds.
The original goal of Cassini-Huygens was to study Saturn and its large, misty, tortured, moon Titan. Titan, the second-largest moon in our Solar System, after Ganymede of Jupiter, is a world long-shrouded in mystery, hiding behind a thick orange veil, and slashed with hydrocarbon lakes and seas. However, there are other enticing moons known to circle the ringed planet. Saturn's mid-sized icy moons (Mimas, Enceladus, Tethys, Dione, Rhea, Hyperion, Iapetus, and Phoebe) are enchanting worlds. Each one of these frozen little moons reveals an interesting and unique geology. So far, Saturn is known to sport 62 icy moons! Ganymede: Ganymede is both the largest moon of Jupiter, our Solar System's planetary behemoth, as well as the largest moon in our entire Solar system. Observations of Ganymede by the HST in 2015 suggested the existence of a subsurface saline ocean. This is because patterns in auroral belts and rocking of the magnetic field hinted at the presence of an ocean. It is estimated to be approximately 100 kilometers deep with a surface situated below a crust of 150 kilometers. Enshrouded in a dense golden hydrocarbon mist, Saturn's largest moon Titan is a mysterious mesmerizing world in its own right. For centuries, Titan's veiled, frigid surface was completely camouflaged by this hazy golden-orange cloud-cover that hid its icy surface from the prying eyes of curious observers on Earth. However, this misty moisty moon-world was finally forced to show its mysterious face, long-hidden behind its obscuring veil of fog, when the Cassini Spacecraft's Huygens Probe landed on its surface in 2004, sending revealing pictures back to astronomers on Earth. In September 2018, astronomers announced that new data obtained from Cassini show what appear to be gigantic, roaring dust storms, raging through the equatorial regions of Titan. The discovery, announced in the September 24, 2018 issue of the journal Nature Geoscience, makes this oddball moon-world the third known object in our Solar System--in addition to Earth and Mars--where ferocious dust storms have been observed. The observations are now shedding new light on the fascinating and dynamic environment of Titan, which is the second largest moon in our Solar System, after Ganymede of Jupiter.