Editing EXOSAT (section)

{{Short description|Space observatory}}
{{Expand language|topic=|langcode=fr|date=June 2021}}
{{Infobox spaceflight
| name                  = EXOSAT
| image                 = exosat.jpg
| image_caption         = EXOSAT

| mission_type          = Astronomy
| operator              = [[European Space Agency|ESA]]
| website               = {{url|http://www.esa.int/export/esaSC/120394_index_0_m.html}}
| COSPAR_ID             = 1983-051A
| SATCAT                = 14095
| mission_duration      = 3 years

| spacecraft_bus        = 
| manufacturer          = [[Messerschmitt-Bölkow-Blohm|MBB]]
| dry_mass              = 
| launch_mass           = {{convert|510.0|kg|lb|abbr=on}}
| power                 = 165.0&nbsp;watts

| launch_date           = {{start-date|26 May 1983, 15:18:00|timezone=yes}}&nbsp;UTC
| launch_rocket         = [[Delta 3000|Delta 3914]] D169
| launch_site           = [[Vandenberg Air Force Base|Vandenberg]] [[Vandenberg AFB Space Launch Complex 2|SLC-2W]]
| launch_contractor     =

| disposal_type         = 
| deactivated           = 
| last_contact          = 
| decay_date            = {{end-date|5 May 1986}}

| orbit_epoch           = 26 May 1983, 11:18:00 UTC<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1983-051A |title=EXOSAT |work=NASA Space Science Data Coordinated Archive |publisher=[[NASA]] |access-date=October 23, 2017}}</ref>
| orbit_reference       = [[geocentric orbit|Geocentric]]
| orbit_regime          = [[Low Earth orbit|Low Earth]]
| orbit_periapsis       = {{convert|347|km|mi|abbr=on}}
| orbit_apoapsis        = {{convert|191,709|km|mi|abbr=on}}
| orbit_inclination     = 72.5&nbsp;degrees
| orbit_semimajor       = 
| orbit_eccentricity    = 0.93428
| orbit_period          = 5,435.4&nbsp;minutes
| orbit_RAAN            = 
| orbit_arg_periapsis   = 
| orbit_mean_anomaly    = 
| orbit_mean_motion     = 
| apsis                 = gee

| insignia              = EXOSAT insignia.png
| insignia_caption      = Legacy ESA insignia for the ''EXOSAT'' mission
| insignia_alt          = ''EXOSAT'' mission logo
| insignia_size         = 180x180px
}}

The '''European X-ray Observatory Satellite''' ('''EXOSAT'''), originally named '''HELOS''', was an X-ray telescope operational from May 1983 until April 1986 and in that time made 1780 observations in the [[X-ray]] band of most classes of astronomical object including [[active galactic nuclei]], [[stellar coronae]], [[cataclysmic variable]]s, [[white dwarfs]], [[X-ray binaries]], [[cluster of galaxies|clusters of galaxies]], and [[supernova remnants]].

This [[European Space Agency]] (ESA) satellite for direct-pointing and lunar-occultation observation of X-ray sources beyond the [[Solar System]] was launched into a highly eccentric orbit (apogee 200,000&nbsp;km, perigee 500&nbsp;km) almost perpendicular to that of the Moon on 26 May 1983. The instrumentation includes two low-energy imaging telescopes (LEIT) with Wolter I X-ray optics (for the 0.04–2 keV energy range), a medium-energy experiment using Ar/CO<sub>2</sub> and Xe/CO<sub>2</sub> detectors (for 1.5–50 keV), a Xe/He gas scintillation spectrometer (GSPC) (covering 2–80 keV), and a reprogrammable onboard data-processing computer. Exosat was capable of observing an object (in the direct-pointing mode) for up to 80 hours and of locating sources to within at least 10 arcsec with the LEIT and about 2 arcsec with GSPC.<ref name=Hoff>{{cite journal |author=Hoff HA |title=EXOSAT - The new extrasolar X-ray observatory |journal=J Brit Interplan Soc (Space Chronicle) |date=Aug 1983 |volume=36 |issue=8 |pages=363–7 |url=http://md1.csa.com/partners/viewrecord.php?requester=gs&collection=TRD&recid=A8339971AH&q=&uid=788028604&setcookie=yes |url-status=dead |archive-url=https://web.archive.org/web/20120829162441/http://md1.csa.com/partners/viewrecord.php?requester=gs&collection=TRD&recid=A8339971AH&q=&uid=788028604&setcookie=yes |archive-date=2012-08-29 }}</ref>