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Mission Overview
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The International Ultraviolet Explorer (IUE) was launched
successfully on 26 January 1978, from Cape Canaveral, Florida. The
satellite was developed to provide a general facility for observing
ultraviolet (UV) spectra of astronomical sources over the wavelength
range from about 1150 A to 3200 A. The project has been a joint
undertaking in which the US National Aeronautics and Space
Administration (NASA) provided the spacecraft, the optical and
mechanical components of the scientific instrument, the US ground
observatory and spacecraft control software; the UK Science Research
Council (SRC) in collaboration with University College London (UCL)
provided the television cameras used to record the spectroscopic
data; and the European Space Agency (ESA) provided the solar arrays
and European ground observatory. The image processing software was
developed jointly by NASA and the SRC's Appleton Laboratory. The
satellite has been placed in geosynchronous orbit over the Atlantic
Ocean and is operated for 16h each day, for NASA sponsored
observers, from the US ground observatory located at the Goddard
Space Flight Center (GSFC) near Washington, D.C., and for the
remaining 8h by ESA, for ESA and UK sponsored observers, from the
European ground observatory located near Madrid.
A synchronous orbit has other advantages. Because the Earth subtends
an angle of only 17 degrees the unconstrained area of sky is much
greater than for low orbits and, as its movement along the ecliptic
is at the diurnal rate, the occurrence of occultations is
infrequent. Consequently, over large portions of the sky, neither
long exposures nor the observation of variable phenomena need be
periodically interrupted. A penalty is that in synchronous orbit
observations are normally made in full sunlight so the telescope
must be baffled to ensure adequate rejection of stray sunlight and
earthlight. The offset guiding system can be influenced, however,
and relatively bright guide stars are needed near the Earth's limb.
The IUE mission was terminated on Sept 30, 1996 at 18:42 UT after a
life span of 18 years, 8 months, 4 days, 1 hour and 6 min.
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REFERENCES |
Boggess, A., Bohlin, R.C., Evans, D.C., Freeman, H.R., Gull, T.R., Heap,
S.R., Klinglesmith, D.A., Longanecker, G.R., Sparks, W., West, D.K., Holm,
A.V., Perry, P.M., Schiffer III, F.H., Turnrose, B.E., Wu, C.C., Lane,
A.L., Linsky, J.L., Savage, B.D., Benvenuti, P., Cassatella, A.,Clavel,
J., Heck, A., Macchetto,F., Penston, M.V., Selvelli, C.I., Dunford, E.,
Gondhaleker, P., Oliver, M.B., Sandford, M.C.W., Stickland, D.,
Boksenberg, A., Coleman, C.I., Snijders, M.A.J., Wilson, R., In-Flight
Performance of the IUE, Nature, 275, 377, 1978.
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