Editing Chandra X-ray Observatory (section)

{{Short description|NASA space telescope launched in 1999}}
{{Use American English|date=June 2024}}
{{Use mdy dates|date=June 2024}}
{{Infobox spaceflight
| name               = Chandra X-ray Observatory
| names_list         = Advanced X-ray Astrophysics Facility (AXAF)
| image              = Chandra artist illustration.jpg
| image_caption      = Illustration of Chandra
| image_size         = 275px
| mission_type       = X-ray astronomy
| operator           = [[NASA]]{{\}}[[Smithsonian Astrophysical Observatory|SAO]]{{\}}CXC
| COSPAR_ID          = 1999-040B
| SATCAT             = 25867
| website            = https://chandra.harvard.edu/
| mission_duration   = Planned: 5 years <br> Elapsed: {{time interval|23 July 1999|sep=,}}
| manufacturer       = [[TRW Inc.]]
| launch_mass        = {{convert|12930|lb|kg|-1|order=flip|abbr=on}}<ref name="chandra-quick-facts">{{cite web |url=https://www.nasa.gov/centers/marshall/news/background/facts/cxoquick.html |title=Chandra X-ray Observatory Quick Facts |publisher=Marshall Space Flight Center |access-date=September 16, 2017 |archive-date=February 12, 2022 |archive-url=https://web.archive.org/web/20220212002150/https://www.nasa.gov/centers/marshall/news/background/facts/cxoquick.html }}</ref>
| dry_mass           = {{convert|10560|lb|kg|-1|order=flip|abbr=on}}<ref name="chandra-quick-facts" />
| payload_mass       = 
| dimensions         = Deployed: {{convert|13.8|xx|19.5|m|ft|1|abbr=on}}<ref name="chandraspecs">{{cite web |url=http://chandra.harvard.edu/about/specs.html |title=Chandra Specifications |publisher=NASA/Harvard |access-date=September 3, 2015}}</ref> <br /> Stowed: {{convert|38.7|xx|14.0|ft|m|1|order=flip|abbr=on}}<ref name="chandra-quick-facts" />
| power              = 2,350 W<ref name="chandraspecs" />
| launch_date        = {{start-date|July 23, 1999, 04:30:59.984}}&nbsp;UTC<ref name="spacefacts">{{cite web |url=http://www.spacefacts.de/mission/english/sts-93.htm |title=International Flight No. 210: STS-93 |work=Spacefacts.de |access-date=April 29, 2018}}</ref>
| launch_rocket      = {{OV|Columbia}} ([[STS-93]])
| launch_site        = [[Kennedy Space Center|Kennedy]], [[Kennedy Space Center Launch Complex 39B|LC-39B]]
| entered_service    = 
| disposal_type      = <!--deorbited, decommissioned, placed in a graveyard orbit, etc-->
| deactivated        = <!--when craft was decommissioned-->
| last_contact       = <!--when last signal received if not decommissioned-->
| decay_date         = <!--when craft re-entered the atmosphere, not needed if it landed-->
<!--{{end-date||timezone=yes}}&nbsp;UTC-->| orbit_reference    = [[Geocentric orbit|Geocentric]]
| orbit_regime       = [[Highly elliptical orbit|Highly elliptical]]
| orbit_semimajor    = {{convert|80795.9|km|mi|abbr=on}}
| orbit_eccentricity = 0.743972
| orbit_periapsis    = {{convert|14307.9|km|mi|abbr=on}}
| orbit_apoapsis     = {{convert|134527.6|km|mi|abbr=on}}
| orbit_inclination  = 76.7156°
| orbit_period       = 3809.3 min
| orbit_RAAN         = 305.3107°
| orbit_arg_periapsis = 267.2574°
| orbit_mean_anomaly = 0.3010°
| orbit_mean_motion  = 0.3780 rev/day
| orbit_epoch        = September 4, 2015, 04:37:54&nbsp;UTC<ref name="heavens-above">{{cite web |url=http://www.heavens-above.com/orbit.aspx?satid=25867 |title=Chandra X-Ray Observatory - Orbit |work=Heavens Above |date=September 3, 2015 |access-date=September 3, 2015}}</ref>
| orbit_rev_number   = 1358
| apsis              = gee
| telescope_type     = [[Wolter telescope|Wolter type 1]]<ref name="cxc-overview">{{cite web |url=http://cxc.harvard.edu/cdo/about_chandra/overview_cxo.html |title=The Chandra X-ray Observatory: Overview |publisher=Chandra X-ray Center |access-date=September 3, 2015}}</ref>
| telescope_diameter = {{convert|3.9|ft|m|order=flip|abbr=on}}<ref name="chandraspecs" />
| telescope_focal_length = {{convert|32.8|ft|m|order=flip|abbr=on}}<ref name="chandraspecs" />
| telescope_area     = {{convert|0.04|m2|abbr=on}}<ref name="chandraspecs" />
| telescope_wavelength = [[X-ray]]: 0.12–12&nbsp;[[nanometre|nm]] (0.1–10&nbsp;[[kiloelectronvolt|keV]])<ref name="Ridpath2012">{{cite book |url=https://books.google.com/books?id=O31j9UJ3U4oC&pg=PA82 |title=The Dictionary of Astronomy |publisher=Oxford University Press |first=Ian |last=Ridpath |edition=2nd |page=82 |date=2012 |isbn=978-0-19-960905-5}}</ref>
| telescope_resolution = 0.5 arcsec<ref name="chandraspecs" />
| instruments_list   = {{Infobox spaceflight/Instruments
   | acronym1 = ACIS | name1 = [[Advanced CCD Imaging Spectrometer]]
   | acronym2 = HRC  | name2 = High Resolution Camera
   | acronym3 = HETG | name3 = High Energy Transmission Grating
   | acronym4 = LETG | name4 = Low Energy Transmission Grating
 }}
| programme             = '''[[Great Observatories program|NASA Great Observatories]]'''
| previous_mission      = [[Compton Gamma Ray Observatory|Compton]]
| next_mission          = [[Spitzer Space Telescope|Spitzer]]
| programme2            = '''[[Large Strategic Science Missions]]'''<br><small>''Astrophysics Division''</small>
| previous_mission2     = [[Compton Gamma Ray Observatory|Compton]]
| next_mission2         = [[James Webb Space Telescope|JWST]]
}}

The '''Chandra X-ray Observatory''' ('''CXO'''), previously known as the '''Advanced X-ray Astrophysics Facility''' ('''AXAF'''), is a [[Flagship program|Flagship-class]] [[space telescope]] launched aboard the {{OV|102}} during [[STS-93]] by [[NASA]] on July 23, 1999. Chandra is sensitive to [[X-ray astronomy|X-ray sources]] 100 times fainter than any previous [[X-ray telescope]], enabled by the high [[angular resolution]] of its mirrors. Since the [[Earth's atmosphere]] absorbs the vast majority of [[X-ray]]s, they are not detectable from Earth-based [[telescope]]s; therefore space-based telescopes are required to make these observations. Chandra is an Earth [[satellite]] in a 64-hour orbit, and its mission is ongoing {{as of|2025|lc=y}}. Chandra is one of the [[Great Observatories program|Great Observatories]], along with the [[Hubble Space Telescope]], [[Compton Gamma Ray Observatory]] (1991–2000), and the [[Spitzer Space Telescope]] (2003–2020). The telescope is named after the Nobel Prize-winning Indian-American astrophysicist [[Subrahmanyan Chandrasekhar]].<ref name="cowinners1998" /> Its mission is similar to that of [[ESA]]'s [[XMM-Newton]] spacecraft, also launched in 1999 but the two telescopes have different design foci, as Chandra has a much higher angular resolution and XMM-Newton higher spectroscopy throughput.

In response to a decrease in NASA funding in 2024 by the [[United States Congress|US Congress]], Chandra is threatened with an early cancellation despite having more than a decade of operation left. The cancellation has been referred to as a potential "extinction-level" event for [[X-ray astronomy]] in the US.{{Citation needed|date=April 2025}} A group of astronomers have put together a public outreach project to try to get enough American citizens to persuade the US Congress to provide enough funding to avoid early termination of the observatory.<ref>{{cite web |title=Act Now |url=https://www.savechandra.org/act |website=Save the Chandra X-ray Observatory |access-date=May 25, 2024 }}</ref>