* Mission Overview

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.

* Instrumentation

The links in the following table go to the respective experiment pages at the NSSDC.
Major Skylab Astronomical Experiments
EXPScientific Objective
H-alphaStudy H-alpha emission from the Sun during solar flares
S009Cosmic Ray flux measurement - nuclear emulsion detector
S019UV line spectra of young, hot stars and galaxies
S020UV and X-ray solar photography for highly ionized atoms
S052Analysis of solar corona
S054X-ray spectrography of solar flares and active regions
S055Chromospheric and coronal extreme UV photography
S056X-ray emissions of lower solar corona
S073Gegenshein and zodiacal light intensity and polarization
S082AStudy of inner corona structure via spectroheliography
S082BSpectrographs of coronal and chromospheric transition region
S149Mass, speed and chemical composition of interplanetary dust
S150Faint X-ray source survey
S183UV Panorama Experiment - photometer for stellar spectrographyand a wide-field imaging camera
S201Far-UV Electrographic camera to study Comet Kohoutek structure
S228Transuranic Cosmic Ray Experiment


SIV-B 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 sq-cm) 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.

* Science

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.

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