PDS_VERSION_ID = PDS3 OBJECT = MISSION MISSION_NAME = "INTERNATIONAL ULTRAVIOLET EXPLORER" OBJECT = MISSION_INFORMATION MISSION_START_DATE = 1978-01-26 MISSION_STOP_DATE = 1996-09-30 MISSION_ALIAS_NAME = "INTERNATIONAL UV EXPLORER" MISSION_DESC = " 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. " MISSION_OBJECTIVES_SUMMARY = " Design Concepts =============== It was decided that a high spectral resolution of the order of 0.2 A would be required to study the atmospheric characteristics of bright stars and planets and that a lower resolution of about 6 A should be available to obtain information on faint sources. In addition, two other requirements were fundamental in determining the design of the scientific instrument and of the spacecraft to support it: first, the instrument should be able to record simultaneous data over large spectral ranges and, second, the spacecraft should be able to take maximum advantage of the observer's real-time judgement concerning the quality and content of his data. The latter requires good communication between the spacecraft and the observer so a geosynchronous orbit was chosen. The IUE orbit allows continuous real-time control from the NASA control centre and at least 10h each day from the ESA control centre. The arrangement is fundamentally different from low altitude orbiting observatories which have to acquire data while remote from ground control. In the case of IUE, control and performance monitoring are exercised continuously. The telescope field is displayed to the observer, who identifies his target star and directs the course of the observation in real-time. The 'IUE observatory', thus comprises the ground control centre, where the astronomer views his television monitors, and the optical and electronic instrumentation located in synchronous orbit." END_OBJECT = MISSION_INFORMATION OBJECT = MISSION_HOST INSTRUMENT_HOST_ID = "IUE" OBJECT = MISSION_TARGET TARGET_NAME = "JUPITER" END_OBJECT = MISSION_TARGET OBJECT = MISSION_TARGET TARGET_NAME = "SL9" END_OBJECT = MISSION_TARGET OBJECT = MISSION_TARGET TARGET_NAME = "COMET" END_OBJECT = MISSION_TARGET END_OBJECT = MISSION_HOST OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "BOGGESSETAL1978A" END_OBJECT = MISSION_REFERENCE_INFORMATION END_OBJECT = MISSION END