Editing Cosmic Background Explorer (section)

{{Short description|NASA satellite of the Explorer program}}
{{Use American English|date=January 2014}}
{{Use dmy dates|date=November 2021}}
{{Infobox spaceflight
| name              = Cosmic Background Explorer
| names_list        = Explorer 66<br/>COBE
| image             = Cosmic Background Explorer spacecraft model.png
| image_caption     = Artist's concept of the COBE spacecraft
| image_size        = 300px

| mission_type      = [[Cosmic microwave background]] [[Radio astronomy|Astronomy]]
| operator          = [[NASA]]
| COSPAR_ID         = 1989-089A
| SATCAT            = 20322
| website           = {{url|1=http://lambda.gsfc.nasa.gov/product/cobe/|2=lambda.gsfc.nasa.gov/product/cobe}}
| mission_duration  = 6 months (planned)<br />{{time interval|18 November 1989 14:34|23 December 1993|show=ymd}} (achieved)

| spacecraft        = Explorer LXVI
| spacecraft_type   = Cosmic Background Explorer
| spacecraft_bus    = COBE
| manufacturer      = [[Goddard Space Flight Center]]
| launch_mass       = {{cvt|2206|kg}} <ref name="gsfcOverview">{{cite web |url=http://lambda.gsfc.nasa.gov/product/cobe/spacecraft_description.cfm |title=COBE Mission Design, Spacecraft and Orbit |date=18 April 2008 |publisher=Goddard Space Flight Center |access-date=21 July 2015}} {{PD-notice}}</ref>
| dry_mass          = {{cvt|1408|kg}} <ref name="pddnet">{{cite web |url=http://www.pddnet.com/articles/2015/07/spacecraft-week-cosmic-background-explorer |title=Cosmic Background Explorer |first=Megan |last=Crouse |date=16 July 2015 |publisher=Product Design & Development |access-date=21 July 2015}}{{Dead link|date=July 2020|bot=InternetArchiveBot|fix-attempted=yes}}</ref>
| dimensions        = {{cvt|5.49|xx|2.44|m}}
| power             = 750 [[watt]]s

| launch_date       = 18 November 1989, 14:34 [[Coordinated Universal Time|UTC]]
| launch_rocket     = [[Delta 5000|Delta 5920-8]] (Delta 189)
| launch_site       = [[Vandenberg Space Force Base|Vandenberg]], [[Vandenberg Space Launch Complex 2|SLC-2W]] 
| launch_contractor = [[Douglas Aircraft Company]]

| entered_service   = 18 November 1989
| last_contact      = 
| deactivated       = 23 December 1993
| decay_date        =

| orbit_reference   = [[Geocentric orbit]]<ref name="Trajectory">{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/displayTrajectory.action?id=1989-089A |title=Trajectory: COBE (1989-089A) |publisher=NASA |date=28 October 2021 |access-date=27 November 2021}} {{PD-notice}}</ref>
| orbit_regime      = [[Sun-synchronous orbit]]
| orbit_periapsis   = {{cvt|900|km}}
| orbit_apoapsis    = {{cvt|900|km}}
| orbit_inclination = 99.00°
| orbit_period      = 103.00 minutes
| apsis             = gee

| instruments       = Differential Microwave Radiometer (DMR)<br />Diffuse Infrared Background Experiment (DIRBE)<br />Far-InfraRed Absolute Spectrophotometer (FIRAS)
 
| insignia          = Cosmic Background Explorer logo.jpg
| insignia_caption  = Cosmic Background Explorer mission patch
| insignia_size     = 200px

| programme         = '''[[Explorers Program|Explorer program]]'''
| previous_mission  = [[AMPTE-CCE]] (Explorer 65)
| next_mission      = [[Extreme Ultraviolet Explorer]] (Explorer 67)
}}

The '''Cosmic Background Explorer''' ('''COBE''' {{IPAc-en|ˈ|k|oʊ|b|i}} {{respell|KOH|bee}}), also referred to as '''Explorer 66''', was a [[NASA]] satellite dedicated to [[physical cosmology|cosmology]], which operated from 1989 to 1993. Its goals were to investigate the [[Cosmic microwave background|cosmic microwave background radiation]] (CMB or CMBR) of the [[universe]] and provide measurements that would help shape the understanding of the [[cosmos]].

COBE's measurements provided two key pieces of evidence that supported the [[Big Bang]] theory of the universe: that the CMB has a near-perfect [[black-body]] [[Electromagnetic spectrum|spectrum]], and that it has very faint [[Anisotropy|anisotropies]]. Two of COBE's principal investigators, [[George F. Smoot III]] and [[John C. Mather]], received the [[Nobel Prize in Physics]] in 2006 for their work on the project. According to the Nobel Prize committee, "the COBE project can also be regarded as the starting point for [[cosmology]] as a precision science".<ref>{{cite web |url=https://www.nobelprize.org/nobel_prizes/physics/laureates/2006/ |title=The Nobel Prize in Physics 2006 |publisher=The Royal Swedish Academy of Sciences |date=2006-10-03 |access-date=2011-08-23}}</ref>

COBE was the second cosmic microwave background satellite, following [[RELIKT-1]], and was followed by two more advanced spacecraft: the [[Wilkinson Microwave Anisotropy Probe]] (WMAP) operated from 2001 to 2010 and the [[Planck (spacecraft)|Planck spacecraft]] from 2009 to 2013.