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Skylab
Skylab, a science and
engineering laboratory, was launched into Earth orbit by a Saturn V
rocket on 14 May 1973. Three crews of 3 men each visited the station,
with their missions lasting 28, 59, and 84 days. Circling 50 degrees
north and south of the equator at an altitude of 435 km, Skylab had an
orbital period of 93 minutes. There were a plethora of UV astronomy
experiments done during the Skylab lifetime, as well as detailed X-ray studies
of the Sun. Skylab fell from orbit on 11 July 1979.
S150
Skylab 3, the second manned mission to Skylab, carried the S150 X-ray
experiment. The S150 was attached to the inside wall of the instrument
unit which was itself mounted atop the SIV-B upper stage of the Saturn
1B rocket which orbited briefly behind and below Skylab on 28 July
1973.
After the astronauts had separated their Apollo capsule
from the SIV-B stage, the S150 experiment was deployed from its
protective housing and activated. The entire SIV-B stage underwent a
series of preprogrammed maneuvers, scanning about 1 degree every 15
seconds, to allow the instrument to sweep across selected regions of
the sky. The pointing direction was determined during data processing,
using the inertial guidance system of the SIV-B stage combined with
information from two visible star sensors which formed part of the
experiment. Data was stored on a tape recorder and replayed to
suitable ground stations when possible.
Galactic X-ray sources were observed with the S150 experiment. The
experiment was designed by Kraushaar, Bunner, and
collaborators at the University of Wisconsin to detect 40-100 angstrom
photons. It consisted of a single large (~ 1500 cm2) proportional
counter, electrically divided by fine wire ground planes into separate
signal-collecting areas and looking through collimator vanes. The
collimators defined 3 intersecting fields of view (~2x20 degrees) on
the sky, which allowed source positions to be determined to ~ 30
arcmin. The front window of the instrument consisted of a 2 micron
thick plastic sheet. The counter gas was a mixture of argon and
methane.
Analysis of the data from the S150 experiment provided strong evidence
that the soft X-ray background cannot be explained as the cumulative
effect of many unresolved point sources.
[Gallery] (http://heasarc.gsfc.nasa.gov/docs/heasarc/missions/images/skylab_images.html)
[Publications] (http://heasarc.gsfc.nasa.gov/docs/heasarc/missions/biblio/skylab_biblio.html)
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