The "unforgettable" Skylab...

Da "NASA - Picture of the Day", del 29 Aprile 2006:"Skylab was an orbiting laboratory launched by NASA in May 1973. Skylab, pictured above, was visited 3 times by NASA Astronauts who sometimes stayed as long as two and a half months. Many scientific tests were performed on Skylab, including astronomical observations in ultraviolet and X-ray light. Some of these observations yielded valuable information about Comet Kohoutek, our Sun and about the mysterious X-ray Background Radiation that (apparently) comes from all over the sky.
Skylab fell back to Earth on July, 11, 1979".