NASA/Marshall Solar Physics

Skylab, the first US space station, was launched into orbit on May 14, 1973 as part of the Apollo program. This 91 metric ton structure was 36 meters (four stories) high, 6.7 meters in diameter and flew at an altitude of 435 km (270 miles). Three different Apollo crews manned Skylab during its 9 month mission: Charles Conrad, Joseph Kerwin, and Paul Weitz from May 25 to June 21, 1973; Alan Bean, Owen Garriott, and Jack Lousma from July 28 to September 24, 1973; and Gerald Carr, Edward Gibson, and William Pogue from November 16, 1973 to February 8, 1974.

Skylab included eight separate solar experiments on its Apollo Telescope Mount: two X-ray telescopes (S-054 sponsored by American Science and Engineering and S-056 sponsored by Marshall Space Flight Center); an X-ray and extreme ultraviolet camera (S-020 sponsored by the Naval Research Laboratory); an ultraviolet spectroheliometer (S-055 sponsored by Harvard College Observatory); an extreme ultraviolet spectroheliograph and an ultraviolet spectroheliograph (S-082A and S-082B sponsored by the Naval Research Laboratory); a white light coronagraph (S-052 sponsored by the High Altitude Observatory); and two hydrogen-alpha telescopes (H-alpha no. 1 sponsored by Harvard College Observatory and H-alpha no. 2 sponsored by Marshall Space Flight Center).

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MSFC Solar Physics Branch members were involved with the soft x-ray telescope, S-056. This grazing incidence telescope produced images of the Sun in x-rays with wavelengths from 6 to 49 Å. Images (84 kb GIF image) taken through 6 different filters were recorded on film which was then returned to Earth with the astronauts for processing. A movie (601 kb mpeg movie) of these images shows some of the discoveries made from Skylab including coronal holes and x-ray bright points. Coronal holes are seen as dark regions in which the hot coronal material is very thin. X-ray bright points are small, compact, short-lived brightenings that are most easily seen in the coronal holes themselves. Coronal holes were observed to rotate fairly rigidly and maintain their shape through several 27-day solar rotations in spite of the variations in rotation rate of the solar surface.

When Skylab was launched it lost a solar panel and part of its external shielding. Skylab astronauts had to rig a "golden umbrella" to keep their habitat comfortable. Skylab re-entered the Earth's atmosphere in 1979 over Australia. This re-entry was a year or two earlier than expected.