International Ultraviolet Explorer

International Ultraviolet Explorer

International Ultraviolet Explorer (Explorer 57) satellite
Names	Explorer 57 IUE SAS-D
Mission type	Ultraviolet astronomy
Operator	NASA / ESA / SERC
COSPAR ID	1978-012A
SATCAT no.	10637
Website	ESA Science and Technology NASA IUE Archive
Mission duration	18 years, 8 months, 4 days[1]
Spacecraft properties
Spacecraft	Explorer LVII
Spacecraft type	International Ultraviolet Explorer
Bus	SAS (Small Astronomy Satellite)
Manufacturer	Goddard Space Flight Center
Launch mass	669 kg (1,475 lb)
Power	424 watts
Start of mission
Launch date	26 January 1978, 17:36:00 UTC
Rocket	Thor-Delta 2914 (Thor 628 / Delta 138)
Launch site	Kennedy Space Center, LC-17A
Contractor	Douglas Aircraft Company
Entered service	3 April 1978
End of mission
Deactivated	30 September 1996
Last contact	30 September 1996, at 18:44 UTC
Orbital parameters
Reference system	Geocentric orbit
Regime	Geosynchronous orbit
Longitude	70.0° West
Main telescope
Type	Ritchey-Chretien Cassegrain reflector
Diameter	45 cm (18 in)
Focal ratio	f/15
Wavelengths	Ultraviolet 115 to 320 nm
Instruments
Particle Flux Monitor (Spacecraft) Ultraviolet Spectrograph Package
ESA patch for the IUE mission Explorer Program ← ISEE-1 (Explorer 56) HCMM (Explorer 58) →

International Ultraviolet Explorer (IUE or Explorer 57, formerly SAS-D),^[2] was the first space observatory primarily designed to take ultraviolet (UV) electromagnetic spectrum. The satellite was a collaborative project between NASA, the United Kingdom's Science and Engineering Research Council (SERC, formerly UKSRC) and the European Space Agency (ESA), formerly European Space Research Organisation (ESRO). The mission was first proposed in early 1964, by a group of scientists in the United Kingdom, and was launched on 26 January 1978 aboard a NASA Thor-Delta 2914 launch vehicle. The mission lifetime was initially set for 3 years, but in the end it lasted 18 years, with the satellite being shut down in 1996. The switch-off occurred for financial reasons, while the telescope was still functioning at near original efficiency.

It was the first space observatory to be operated in real time by astronomers who visited the groundstations in the United States and Spain. Astronomers made over 104,000 observations using the IUE, of objects ranging from Solar System bodies to distant quasars. Among the significant scientific results from IUE data were the first large scale studies of stellar winds, accurate measurements of the way interstellar dust absorbs light, and measurements of the supernova SN 1987A which showed that it defied stellar evolution theories as they then stood. When the mission ended, it was considered the most successful astronomical satellite ever.^[3]