Explorers Program: Difference between revisions

Revision as of 00:19, 3 July 2024

Revision as of 00:34, 29 July 2024

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[[File:Pointing X-ray Eyes at our Resident Supermassive Black Hole.jpg|thumb|upright=1.0|right|An Explorer mission observes [[Sagittarius A*]], the [[Milky Way|Milky Way's]] central [[black hole]], flaring.]]

The '''Explorers program'''<ref>{{cite web |title=Explorers Program |url=https://explorers.gsfc.nasa.gov/ |website=Explorers Program Home Page at NASA Goddard |publisher=NASA |access-date=3 May 2022}} {{PD-notice}}</ref> is a [[NASA]] exploration program that provides flight opportunities for physics, [[geophysics]], [[heliophysics]], and [[astrophysics]] investigations from space. Launched in 1958, [[Explorer 1]] was the first spacecraft of the United States to achieve orbit. Over 90 space missions have been launched since. Starting with [[Explorer 6]], it has been operated by NASA, with regular collaboration with a variety of other institutions, including many international partners.

Launchers for the Explorer program have included [[Juno I]], [[Juno II]], various [[Thor (rocket family)|Thor]], [[Scout (rocket family)|Scout]], [[Delta (rocket family)|Delta]] and [[PegasusNorthrop (rocket)Grumman Pegasus|Pegasus]] launch vehicles, and [[Falcon 9]].

The program has three classes: Medium-Class Explorers (MIDEX), Small Explorers (SMEX), and University-Class Explorers (UNEX), with select Missions of Opportunity operated with other agencies.

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The Explorer program began as a [[United States Army|U.S. Army]] proposal ([[Project Orbiter]]) to place a "civilian" [[satellite|artificial satellite]] into orbit during the [[International Geophysical Year]] (IGY). Although that proposal was rejected in favor of the [[United States Navy|U.S. Navy]]'s [[Project Vanguard]], which made the first sub-orbital flight [[Vanguard TV0]] in December 1956, the [[Soviet Union]]'s launch of [[Sputnik 1]] on 4 October 1957 (and the resulting "[[Sputnik crisis]]") and the failure of the [[Vanguard 1]] launch attempt resulted in the Army program being funded to match the Soviet space achievements. [[Explorer 1]] was launched on the Juno I on 1 February 1958, becoming the first U.S. satellite, as well as discovering the [[Van Allen radiation belt]].

Four follow-up satellites of the Explorer series were launched by the Juno I launch vehicle in 1958, of which [[Explorer 3]] and [[Explorer 4]] were successful, while [[Explorer 2]] and [[Explorer 5]] failed to reach orbit.<ref name=Boehm-NASA>{{citation-attribution|1=J. Boehm, H.J. Fichtner, and Otto A. Hoberg, [https://www.nasa.gov/sites/default/files/atoms/files/explorer_i_boehm_document.pdf EXPLORER SATELLITES LAUNCHED BY JUNO 1 AND JUNO 2 VEHICLES] NASA Report }}</ref> The Juno I vehicle was replaced by the [[Juno II]] in 1959.

=== Continuation of the Explorer program ===

[[File:M101 combined low.jpg|thumb|upright=1.0|right|This artificially colored view of M101 maps ultraviolet light as blue while visible light is red since [[Ultraviolet|UV]] light does not have a "color" (the eye stopping at about violet). This view was taken by the Explorer [[Neil Gehrels Swift Observatory|Swift]], which can also detect X-rays, and has contributed to the study of [[gamma-ray burst]]s and other topics.]]

With the establishment of NASA in 1958, the Explorer program was transferred to NASA from the [[United States Army|U.S. Army]]. NASA continued to use the name for an ongoing series of relatively small space missions, typically an artificial satellite with a specific science focus. [[Explorer 6]] in 1959 was the first scientific satellite under the project direction of NASA's [[Goddard Space Flight Center]] (GSFC) in [[Greenbelt, Maryland]].<ref>{{cite magazine |last=Portree |first=David S. F. |url=https://www.wired.com/2013/05/cometary-explorer-1973/ |title=Cometary Explorer (1973) |magazine=Wired |date=22 May 2013 |access-date=24 June 2019 |url-access=limited}}</ref><ref>{{citation-attribution|1={{cite web |url=https://www.nasa.gov/content/goddard-missions-past |title=Goddard Missions - Past|work=Goddard Space Flight Center |publisher=NASA |date=5 June 2018 |access-date=24 June 2019}} {{PD-notice}}</ref>

The [[Interplanetary Monitoring Platform]] (IMP) was launched in 1963, and involved a network of eleven Explorer satellites designed to collect data on space radiation in support of the [[Apollo program]]. The IMP program was a major step forward in spacecraft [[electronics]] design, as it was the first space program to use [[integrated circuit]] (IC) chips and [[MOSFET]]s (MOS transistors).<ref name="Butrica">{{citation-attribution|1={{cite book |last1=Butrica |first1=Andrew J. |chapter=Chapter 3: NASA's Role in the Manufacture of Integrated Circuits |editor-last1=Dick |editor-first1=Steven J. |title=Historical Studies in the Societal Impact of Spaceflight |date=2015 |publisher=NASA |isbn=978-1-62683-027-1 |pages=149-250 (237-42242) |chapter-url=https://www.nasa.gov/sites/default/files/atoms/files/historical-studies-societal-impact-spaceflight-ebook_tagged.pdf#page=237}} {{PD-notice}}</ref><ref name="nasa">{{citation-attribution|1={{cite book |title=Interplanetary Monitoring Platform |date=29 August 1989 |publisher=NASA |pages=1, 11, 134 |url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19800012928.pdf |access-date=12 August 2019 |last1=Butler |first1=P. M.}} {{PD-notice}}</ref> The IMP-A ([[Explorer 18]]) in 1963 was the first spacecraft to use IC chips, and the IMP-D ([[Explorer 33]]) in 1966 was the first to use MOSFETs.<ref name="Butrica"/>

Over the following two decades, NASA has launched over 50 Explorer missions,<ref name= "nssdc_list"/> some in conjunction to military programs, usually of an exploratory or survey nature or had specific objectives not requiring the capabilities of a major space observatory. Explorer satellites have made many important discoveries on: Earth's [[magnetosphere]] and the shape of its [[Gravitational field|gravity field]]; the [[solar wind]]; properties of [[micrometeoroids]] raining down on the [[Earth]]; ultraviolet, cosmic and X-rays from the [[Solar System]] and beyond; [[Ionosphere|ionospheric physics]]; [[Solar flare|Solar plasma]]; [[solar energetic particles]]; and [[Atmospheric science|atmospheric physics]]. These missions have also investigated air density, radio astronomy, [[geodesy]], and [[gamma-ray astronomy]].

With dropsdecreases in NASA's budget, Explorer missions became infrequent in the early 1980s.

=== SMEX, MIDEX, and Student Explorer programs ===

In 1988, the '''Small Explorer (SMEX)''' class was established with a focus on frequent flight opportunities for highly focused and relatively inexpensive space science missions in the disciplines of astrophysics and space physics.<ref name=NASAhistory>{{cite book |last=Rumerman |first=Judy A. |url=https://history.nasa.gov/SP-4012v7ch4.pdf |title=NASA Historical Data Book, Vol. VII: NASA Launch Systems, Space Transportation, Human Spaceflight, and Space Science, 1989-1998 |publisher=NASA |date=2009 |access-date=24 June 2019}} {{PD-notice}}</ref><ref>{{cite web |url=https://www.nasa.gov/centers/goddard/pdf/106477main_smex.pdf |title=NASA's Small Explorer Program: Faster, Better, Cheaper |work=Goddard Space Flight Center |publisher=NASA |date=January 1998 |access-date=24 June 2019 |archive-date=16 February 2017 |archive-url=https://web.archive.org/web/20170216162632/https://www.nasa.gov/centers/goddard/pdf/106477main_smex.pdf |url-status=dead}} {{PD-notice}}</ref> The first three SMEX missions were chosen in April 1989 out of 51 candidates, and launched in 1992, 1996 and 1998<ref name=IEEE>{{cite conference |title=SAMPEX: NASA's First Small Explorer Satellite |conference=IEEE Aerospace Conference 21–28 March 1998 Aspen, Colorado |first1=G. M. |last1=Mason |first2=D. N. |last2=Baker |first3=J. B. |last3=Blake |first4=R. E. |last4=Boughner |first5=L. B. |last5=Callis |display-authors=et al. |volume=5 |pages=389–412 |date=1998 |doi=10.1109/AERO.1998.685848}}</ref> The second set of two missions were announced in September 1994 and launched in 1998 and 1999.<ref name=NASAhistory/>

In the mid -1990s, NASA initiated the '''Medium-class Explorer (MIDEX)''' to enable more frequent flights. These are larger than SMEX missions and were to be launched aboard a new kind of medium-light class launch vehicle.<ref name=NASAhistory/> This new launch vehicle was not developed and instead, these missions were flown on a modified [[Delta II]] rocket.<ref>{{cite web |author=Ed Kyle |url=http://www.spacelaunchreport.com/delta2.html |archive-url=https://web.archive.org/web/20100325164354/http://www.spacelaunchreport.com/delta2.html |url-status=usurped |archive-date=25 March 2010 |title=Delta II Data Sheet |publisher=Spacelaunchreport.com |access-date=2018-04-28}}</ref><ref>{{cite magazine |url=http://aviationweek.com/awin/nasa-taps-mcdonnell-med-lite-launches |title=NASA Taps Mcdonnell For Med-Lite Launches |magazine=Aviation Week |date=4 March 1996-03-04 |access-date=2018-04-28 April 2018}}</ref> The first announcement opportunity for MIDEX was issued in March 1995, and the first launch under this new class was [[Far Ultraviolet Spectroscopic Explorer|FUSE]] in 1999.<ref name=NASAhistory/>

In May 1994, NASA started the '''Student Explorer Demonstration Initiative''' (STEDI) pilot program, to demonstrate that high-quality space science can be carried out with small, low-cost missions. Of the three selected missions, SNOE was launched in 1998 and TERRIERS in 1999, but the latter failed after launch. The STEDI program was terminated in 2001.<ref name=NASAhistory/> Later, NASA established the '''University-Class Explorer''' (UNEX) program for much cheaper missions, which is regarded as a successor to STEDI.<ref>{{cite web |url=https://web.stanford.edu/~sbuchman/publications-PDF/The%20Large%20Benefits%20of%20Small%20Satellite%20Missions.pdf |title=The Large Benefits of Small Satellite Missions |access-date=2018-04-28}}</ref>

The Explorer missions were at first managed by the Small Explorer Project Office at NASA's Goddard Space Flight Center (GSFC). In early 1999, that office was closed and with the announcement of opportunity for the third set of SMEX missions NASA converted the SMEX class so that each mission was managed by its [[principal investigator]], with oversight by the GSFC Explorer Project.<ref name="welcome">{{citation-attribution|1={{cite web |url=http://sunland.gsfc.nasa.gov/smex/ |title=Welcome to the Small Explorer's Web Site |publisher=NASA |date=18 February 2000 |url-status=dead |archive-url=https://web.archive.org/web/20000817054104/http://sunland.gsfc.nasa.gov/smex/ |archive-date=17 August 2000}} {{PD-notice}}</ref> The Explorer program Office at Goddard Space Flight Center, provides management of the many operational scientific exploration missions that are characterized by relatively moderate costs and small to medium-sized missions that are capable of being built, tested, and launched in a short time interval compared to larger observatories like NASA's [[Great Observatories]].<ref>{{citation-attribution|1={{cite web |url=http://explorers.gsfc.nasa.gov/history.html |title=Explorers Program |website=Explorersexplorers.gsfc.nasa.gov |date=1958-01-31 |access-date=2016-02-24 |archive-url=https://web.archive.org/web/20160304052517/http://explorers.gsfc.nasa.gov/history.html |archive-date=4 March 2016-03-04 |url-status=dead }} {{PD-notice}}</ref>

Excluding the launches, the MIDEX class has a current mission cap cost of US$250 million in 2018,<ref name=Midex19>{{citation-attribution|1={{cite web |url=https://www.nasa.gov/press-release/nasa-selects-proposals-to-study-galaxies-stars-planets |title=NASA Selects Proposals to Study Galaxies, Stars, Planets |date=9 August 2017 |publisher=NASA |access-date=2018-04-28 April 2018}} {{PD-notice}}</ref> with future MIDEX missions being capped at US$350 million.<ref>{{cite web |author=Jeff Foust |url=http://spacenews.com/earth-science-decadal-report-recommends-mix-of-large-and-small-missions/ |title=Earth science decadal report recommends mix of large and small missions |date=5 January 2018 |publisher=SpaceNews |access-date=28 April 2018-04-28}}</ref> The cost cap for SMEX missions in 2017 was US$165 million.<ref>{{citation-attribution|1={{cite web |last1=Wu |first1=Chauncey |last2=Manuel |first2=Greg |last3=Salas |first3=Andrea |url=https://explorers.larc.nasa.gov/HPSMEX/pdf_files/05-2016_Helio_PPC_TMC_Wu_v2.pdf |title=2016 Heliophysics Small Explorer (SMEX) & Mission of Opportunity (MO) Solicitations Pre-Proposal Conference |publisher=NASA |date=15 August 2016 |access-date=24 June 2019}} {{PD-notice}}</ref> UNEX missions are capped at US$15 million.<ref name=missions>{{citation-attribution|1={{cite web |url=http://explorers.gsfc.nasa.gov/missions.html |title=Explorer Missions |publisher=NASA |access-date=28 August 2015 |url-status=dead |archive-url=https://web.archive.org/web/20100323182500/http://explorers.gsfc.nasa.gov/missions.html |archive-date=23 March 2010}} {{PD-notice}}</ref> A sub-project called '''Missions of Opportunity''' (MO) has funded science instruments or hardware components of onboard non-NASA space missions, and have a total NASA cost cap of US$70 million.<ref name=Midex19/><ref name=missions/>

== Classes ==

=== Medium-Class Explorers (MIDEX) ===

{| class="wikitable"

|+List of MIDEX missions<ref>{{cite web |url=http://explorers.gsfc.nasa.gov/midex.html |title=Explorers Program |website=explorers.gsfc.nasa.gov |access-date=8 April 2016-04-08 |archive-url=https://web.archive.org/web/20160323014953/http://explorers.gsfc.nasa.gov/midex.html |archive-date=2016-03-23 March 2016 |url-status=dead}} {{PD-notice}}</ref><ref name=":0" /><ref>{{cite web |url=https://explorers.larc.nasa.gov/MIDEX/MIDEX.html |title=Medium-class Explorers (MIDEX) |publisher=Explorers.larc.nasa.gov |access-date=28 April 2018}} {{PD-04-28notice}}</ref>

|-

! Name

Line 80:

| MIDEX-2

| Explorer-80

| June 30, June 2001

| Ended in 2010

|-

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| MIDEX-3

| Explorer-84

| November 20, November 2004

| {{success|'''Operational'''}}

|-

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| MIDEX-5A

| Explorer-85

| February 17, February 2007

| {{success|'''Operational'''}}

|-

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| MIDEX-5B

| Explorer-86

| February 17, February 2007

| {{success|'''Operational'''}}

|-

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| MIDEX-5C

| Explorer-87

| February 17, February 2007

| {{success|'''Operational'''}}

|-

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| MIDEX-5D

| Explorer-88

| February 17, February 2007

| {{success|'''Operational'''}}

|-

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| MIDEX-5E

| Explorer-89

| February 17, February 2007

| {{success|'''Operational'''}}

|-

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| MIDEX-6

| Explorer-92

| December 14, December 2009

| {{success|'''Operational'''}}<ref>[https://www.nasa.gov/feature/jpl/neowise-celebrates-five-years-of-asteroid-data/ NEOWISE Celebrates Five Years of Asteroid Data]. NASA. 15 April 2019. {{PD-notice}}</ref>

|-

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| MIDEX-7

| Explorer-95

| April 18, April 2018

| {{success|'''Operational'''}}

|-

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|

| April 2025

| {{pending|In development<ref>{{cite web |url=https://www.jpl.nasa.gov/missions/spherex |title=Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer |work=[[Jet Propulsion Laboratory|JPL]] |publisher=[[NASA]] |access-date=7 July 2021}} {{PD-notice}}</ref>}}

|-

| [[UVEX]]

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|}

=== Small Explorers (SMEX) ===

The Small Explorers class was implemented in 1989 specifically to fund space exploration missions that cost no more than {{US$|120 million}}.<ref name=missions/><ref name="IEEE" /> The missions are managed by the Explorers Project at the [[Goddard Space Flight Center]] (GSFC).<ref name="welcome" />

The first set of three SMEX missions were launched between 1992 and 1998. The second set of two missions were launched in 1998 and 1999. These early missions were managed by the Small Explorer Project Office at Goddard Space Flight Center. In early 1999, that office was closed and with the announcement of opportunity for the third set of SMEX missions NASA converted the program so that each mission was managed by its [[Principal investigator|Principal Investigator]], with oversight by the GSFC Explorers Project.<ref name="welcome" />

NASA funded a competitive study of five candidate heliophysics Small Explorers missions for flight in 2022. The proposals were Mechanisms of Energetic Mass Ejection – eXplorer (MEME-X), Focusing Optics X-ray Solar Imager (FOXSI), Multi-Slit Solar Explorer (MUSE), Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites (TRACERS), and Polarimeter to Unify the Corona and Heliosphere (PUNCH).<ref>{{cite web |url=https://www.nasa.gov/press-release/nasa-selects-proposals-to-study-sun-space-environment |title=NASA Selects Proposals to Study Sun, Space Environment |publisher=NASA |first=Dwayne |last=Brown |date=28 July 2017 |access-date=7 December 2017}} {{PD-notice}}</ref><ref>{{cite web |url=https://nspires.nasaprs.com/external/viewrepositorydocument/cmdocumentid=524225/solicitationId=%7BA0C496AC-9B9D-8F7D-A506-B1695BF9BDE8%7D/viewSolicitationDocument=1/2016%20Helio%20SMEX%20AO_amend1_clarify.pdf |title=Announcement of Opportunity: Heliophysics Explorers Program, 2016 Small Explorer (SMEX) |publisher=NASA |date=13 July 2016 |id=NNH16ZDA005O}} {{PD-notice}}</ref><ref>{{cite web |url=https://explorers.larc.nasa.gov/HPSMEX/pdf_files/8_SMEX-AO-2016Helio-CSR-Kickoff-LSP-MENDOZA-HILL.pdf |title=Heliophysics Small Explorers 2016 Announcement of Opportunity: Concept Study Report Kickoff |publisher=NASA{{\}}Launch Services Program |first=Alicia |last=Mendoza-Hill |date=25 August 2017}} {{PD-notice}}</ref> In June 2019 NASA selected TRACERS and PUNCH for flight.<ref>{{cite web |url=https://www.nasa.gov/press-release/nasa-selects-missions-to-study-our-sun-its-effects-on-space-weather |title=NASA Selects Missions to Study Our Sun, Its Effects on Space Weather |publisher=NASA |date=20 June 2019 |url-status=live |archive-url=https://web.archive.org/web/20231031190231/https://www.nasa.gov/news-release/nasa-selects-missions-to-study-our-sun-its-effects-on-space-weather/ |archive-date= Oct 31, October 2023}} {{PD-notice}}</ref>

{| class="wikitable"

|+List of SMEX missions <ref name=":0">{{cite web |url=http://space.skyrocket.de/doc_sat/explorer.htm |title=Explorer Program |website=space.skyrocket.de |access-date=8 April 2016}}</ref><ref>{{citation-attribution|1={{cite web |url=http://explorers.gsfc.nasa.gov/smex.html |title=Operational Small Explorers (SMEX) Missions |website=Explorer Program |access-date=8 April 2016 |archive-url=https://web.archive.org/web/20160325193350/http://explorers.gsfc.nasa.gov/smex.html |archive-date=25 March 2016 |url-status=dead}} {{PD-notice}}</ref>

|-

! Name

Line 188:

|

| 2 July 1996

| <ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1996-037A |title=NASA - NSSDCA - Spacecraft - Details|publisher=NASA |date=21 March 2017 |access-date=20 April 2018}} {{PD-notice}}</ref>

-->

|-

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| ''Scheduled for 2005''

| {{n/a}}

| Cancelled in 2003 due to poor instrument sensitivity <ref>{{cite web |url=http://www.spacetoday.net/Summary/1695 |title=NASA cancels space science mission |website=spacetoday.net |date=4 June 2003 |access-date=28 April 2018 |url-status=live |archive-url=https://web.archive.org/web/20190427111301/http://www.spacetoday.net/Summary/1695 |archive-date=27 Apr 27,April 2019 }}</ref>

|-

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| ''Scheduled for 2014''

| {{n/a}}

| Cancelled in 2012 due to expected cost overruns<ref>{{cite web |last1=Berger |first1=Brian |first2=Dan |last2=Leone |agency=Space News |url=https://www.space.com/16041-gems-spacecraft-nasa-cancellation.html |title=GEMS Spacecraft Team Appeals NASA Cancellation Decision |publisher=Space.com |date=7 June 2012 |access-date=28 April 2018}}</ref>

|-

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|

|

| April 2025<ref>{{cite web |last=Foust |first=Jeff |url=https://spacenews.com/nasa-selects-spacex-for-rideshare-launch-of-smallsat-mission/ |title=NASA selects SpaceX for rideshare launch of smallsat mission |work=[[SpaceNews]] |date=30 September 2023 |access-date=1 October 2023 |url-status=live |archive-url=https://archive.today/20231219234720/https://spacenews.com/nasa-selects-spacex-for-rideshare-launch-of-smallsat-mission/ |archive-date= 19 December 2023 }}</ref>

|

| {{pending|In development}}

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|

|

| April 2025<ref name="nasa-20220803">{{cite web |last=Interrante |first=Abbey |url=https://blogs.nasa.gov/punch/2022/08/03/punch-announces-rideshare-with-spherex-and-new-launch-date/ |title=PUNCH Announces Rideshare with SPHEREx and New Launch Date |date=3 August 2022 |access-date=3 August 2022 |work=[[NASA]]}} {{PD-notice}}</ref>

|

| {{pending|In development}}

Line 315:

|

|

| August 2027<ref>{{cite press release |url=https://www.nasa.gov/news-release/nasa-awards-launch-services-contract-for-space-telescope-mission/ |title=NASA Awards Launch Services Contract for Space Telescope Mission |work=[[NASA]] |date=2 July 2024 |access-date=3 July 2024}} {{PD-notice}}</ref>

|

| {{pending|In development}}

Line 327:

</gallery>

=== University-Class Explorers (UNEX) ===

{| class="wikitable"

|+List of UNEX missions<ref name=":1">{{cite web |url=http://explorers.gsfc.nasa.gov/unex_mo_intern.html |title=Explorers Program |website=explorers.gsfc.nasa.gov |access-date=2016-04-08 |archive-url=https://web.archive.org/web/20160322091118/http://explorers.gsfc.nasa.gov/unex_mo_intern.html |archive-date=2016-03-22 March 2016 |url-status=dead}} {{PD-notice}}</ref>

|-

! Name

Line 347:

| {{center|—}}

| ''Scheduled for 2003''

| Cancelled before 2005 (cost)<ref name="nap">{{cite book |url=https://www.nap.edu/read/11530/chapter/8#54 |title=6 Lessons Learned from PI-Led Mission Experiences &#124; Principal-Investigator-Led Missions in the Space Sciences &#124; The National Academies Press |doi=10.17226/11530 |publisher=Nap.edu |date=2006 |isbn=978-0-309-10070-0 |access-date=2018-04-28 April 2018}}</ref>

|-

Line 357:

|}

=== Missions of Opportunity (MO) ===

Missions of Opportunity (MO) are investigations characterized by being part of a non-NASA space mission of any size and having a total NASA cost of under $55 million. These missions are conducted on a no-exchange-of-funds basis with the organization sponsoring the mission. NASA solicits proposals for Missions of Opportunity on SMEX, MIDEX and UNEX investigations.<ref>[https://explorers.gsfc.nasa.gov/missions.html Explorers Missions: Missions of Opportunity (MO)] NASA [[Goddard Space Flight Center]] (GSFC). Accessed on 18 August 2019. {{PD-notice}}</ref>

{| class="wikitable"

Line 371:

| NASA (Explorer-79)

| 9 October 2000

| Ended in 2008<ref>{{citation-attribution|1={{cite web |url=https://heasarc.gsfc.nasa.gov/docs/hete2/hete2.html |title=The HETE-2 Satellite |publisher=NASA |access-date=2018-04-28 April 2018}} {{PD-notice}}</ref>

|-

| [[INTEGRAL]]

| [[ESA]]<ref>{{citation-attribution|1={{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=2002-048A |title=NASA - NSSDCA - Spacecraft |publisher=NASA |access-date=2018-04-20 April 2018}} {{PD-notice}}</ref>

| 17 October 2002

| {{success|'''Operational'''}}

|-

| [[Suzaku (satellite)|Suzaku]] (Astro-E2)

| [[JAXA]]<ref>{{citation-attribution|1={{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=2005-025A |title=NASA - NSSDCA - Spacecraft |publisher=NASA |date=2017-03-21 March 2017 |access-date=2018-04-20 April 2018}} {{PD-notice}}</ref>

| 10 July 2005

| Ended in 2015

|-

| [[TWINS]]

| [[National Reconnaissance Office|NRO]] ([[USA-184]];<ref>{{citation-attribution|1={{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=2006-027A |title=NASA - NSSDCA - Spacecraft |publisher=NASA |access-date=2018-04-20}} {{PD-notice}}</ref><br/>[[USA-200]]<ref>{{citation-attribution|1={{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=2008-010A |title=NASA - NSSDCA - Spacecraft |publisher=NASA |access-date=2018-04-20}} {{PD-notice}}</ref>)

| TWINS-1: 28 June 2006<br/>TWINS-2: 13 March 2008

| {{success|'''Operational'''}}

|-

| [[CINDI]]

| [[DoD]] ([[C/NOFS]])<ref>{{citation-attribution|1={{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=2008-017A |title=NASA - NSSDCA - Spacecraft |publisher=NASA |date=2017-03-21 |access-date=2018-04-20}} {{PD-notice}}</ref>

| 16 April 2008

| Ended in 2015

|-

| [[Hitomi (satellite)|Hitomi]] (Astro-H)

| [[JAXA]]<ref>{{citation-attribution|1={{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=2016-012A |title=NASA - NSSDCA - Spacecraft |publisher=NASA |date=2017-03-21 |access-date=2018-04-20}} {{PD-notice}}</ref>

| 17 February 2016

| {{failure|Failed}}

Line 421:

| NASA, high-altitude balloon

| December 2023

| {{pending|In development<ref>{{cite web |url=https://www.nasa.gov/content/galacticextragalactic-uldb-spectroscopic-terahertz-observatory-gusto/ |title=Galactic/Extragalactic ULDB Spectroscopic Terahertz Observatory (GUSTO) |work=[[NASA]] |access-date=11 March 2023}} {{PD-notice}}</ref><ref>{{cite web |url=https://www.nasa.gov/press-release/nasa-selects-mission-to-study-churning-chaos-in-our-milky-way-and-beyond |title=NASA Selects Mission to Study Churning Chaos of Nearby Cosmos &#124; NASA |publisher=Nasa.govNASA |date= 2017-03-24 |access-date=2018-04-20}} {{PD-notice}}</ref>}}

|-

| [[Sun Radio Interferometer Space Experiment|SunRISE]]

| [[NASA]] ([[Maxar]] satellite)

| April 2024

| {{pending|In development<ref>{{cite web |last=Ng |first=Joy |url=https://blogs.nasa.gov/sunspot/2021/09/09/nasas-sunrise-mission-studying-solar-particle-storms-moves-toward-launch/ |title=NASA's SunRISE Mission Studying Solar Particle Storms Moves Toward Launch |work=[[NASA]] |date=9 September 2021 |access-date=9 September 2021}} {{PD-notice}}</ref><ref>{{cite press release |last1=Hautaluoma |first1=Grey |last2=Fox |first2=Karen |url=https://www.nasa.gov/press-release/nasa-selects-mission-to-study-causes-of-giant-solar-particle-storms |title=NASA Selects Mission to Study Causes of Giant Solar Particle Storms |publisher=[[NASA]] |date=30 March 2020 |access-date=31 March 2020}} {{PD-notice}}</ref>}}

|-

| [[Electrojet Zeeman Imaging Explorer|EZIE]]

| [[NASA]], [[JHUAPL]]

| June 2024

| {{pending|In development<ref>{{cite press release |url=https://www.jhuapl.edu/PressRelease/201229-NASA-selects-EZIE-heliophysics |title=Johns Hopkins APL Space Weather Mission Selected by NASA |publisher=[[JHUAPL]] |date=29 December 2020 |access-date=30 December 2020}}</ref>}}

|-

| [[Solar-C EUVST]]

| [[JAXA]]

| July 2028

| {{pending|In development<ref>{{cite press release |last1=Hautaluoma |first1=Grey |last2=Frazier |first2=Sarah |url=https://www.nasa.gov/press-release/nasa-approves-heliophysics-missions-to-explore-sun-earth-s-aurora |title=NASA Approves Heliophysics Missions to Explore Sun, Earth's Aurora |publisher=[[NASA]] |date=29 December 2020 |access-date=30 December 2020}} {{PD-notice}}</ref><ref>{{cite conference |last=Shimizu |first=Toshifumi |url=https://agu.confex.com/agu/fm23/meetingapp.cgi/Paper/1295860 |title=SH54A-03 The SOLAR-C EUVST mission: Coronal physics advanced by novel EUV spectroscopy |conference=[[American Geophysical Union| (AGU23]]) |date=15 December 2023 |access-date=26 December 2023}}</ref>}}

|-

| [[Contribution to ARIEL Spectroscopy of Exoplanets|CASE]]

| [[ESA]] ([[Cosmic Vision]] [[ARIEL|M4]])

| 2029

| {{pending|In development<ref>{{cite web |last=Landau |first=Elizabeth |url=https://www.nasa.gov/feature/jpl/nasa-instrument-to-probe-planet-clouds-on-european-mission |title=NASA Instrument to Probe Planet Clouds on European Mission |publisher=[[NASA]] |date=8 November 2019 |access-date=12 November 2019}} {{PD-notice}}</ref><ref>{{Cite journal |arxiv = 1906.02820 |doi = 10.1088/1538-3873/ab2d54 |title = Constraining Exoplanet Metallicities and Aerosols with the Contribution to ARIEL Spectroscopy of Exoplanets (CASE) |journal = Publications of the Astronomical Society of the Pacific |volume =131 131|issue =1003 1003|pages =094401 094401|year =2019 2019|last1 =Zellem Zellem|first1 = Robert T. |display-authors=etalet al. |bibcode = 2019PASP..131i4401Z |s2cid = 174801052}} {{PD-notice}}</ref>}}

|}

=== Beacon Explorers{{anchor|Beacon}} ===

Three satellites were planned in this series: [[Beacon Explorer-A]], [[Beacon Explorer-B]], [[Beacon Explorer-C]].

=== GEOS series ===

A series of three Geodetic Earth Orbiting Satellite (GEOS) were put in orbit: [[GEOS 1]], [[GEOS 2]], [[GEOS 3]].

== Launched spacecraft ==

Explorer name numbers can be found in the [[NASA Space Science Data Coordinated Archive|NSSDC master catalog]], typically assigned to each spacecraft in a mission. These numbers were not officially assigned until after 1975.<ref>{{cite web |url=http://www.planet4589.org/space/misc/explorer.html |title=Explorer Program |website=planet4589.org |access-date=2016-02-24 |archive-url=https://web.archive.org/web/20160303194728/http://www.planet4589.org/space/misc/explorer.html |archive-date=2016-03-03 |url-status=dead}}</ref>

{| class="wikitable sortable" style="margin:1em auto;"

|+ '''Explorers Program satellites'''<ref name= "nssdc_list">{{cite web |url=https://nssdc.gsfc.nasa.gov/multi/explorer.html |title=NASA's Explorer Program Satellites |publisher=National Space Science Data Center |access-date=2018-04-20}} {{PD-notice}}</ref><ref>{{cite web |url=http://www.planet4589.org/space/misc/explorer.html |title=Explorer Program |publisher=Planet4589.org |access-date=2018-04-20 |archive-url=https://web.archive.org/web/20160303194728/http://www.planet4589.org/space/misc/explorer.html |archive-date=2016-03-03 |url-status=dead}}</ref><ref>{{cite web |url=https://history.nasa.gov/explorer.html |title=Explorer Spacecraft Series |publisher=History.nasa.gov |access-date=2018-04-20}} {{PD-notice}}</ref><ref name=skyrocket>{{cite web |url=http://space.skyrocket.de/doc_sat/explorer.htm |title=Explorer Program |website=space.skyrocket.de |access-date=2016-02-24}}</ref>

|-

Line 464:

! Orbit regime

! End of data

! Re-entry<br><ref>{{cite web |url=http://www.unoosa.org/oosa/osoindex/search-ng.jspx?match=explorer |title=Search OSOidx |publisher=Unoosa.org |date=2018-04-23 |access-date=2018-04-28}}</ref>

! Mission/Notes

|-

Line 476:

| 23 May 1958

| 31 March 1970

| First American satellite, third satellite to achieve orbit; discovered the [[Van Allen radiation belt]]; launched by the [[United States Army|U.S. Army]]<ref>{{citation-attribution|1={{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1958-001A |title=Explorer 1 (1958-001A) |publisher=NASA |date=7 January 2022 |access-date=12 February 2022}} {{PD-notice}}</ref>

|- style="background:#fbb;"

Line 487:

| —

| —

| Failed to achieve orbit.<ref>{{citation-attribution|1={{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=EXPLR2 |title=Explorer 1 (EXPLR2) |publisher=NASA |date=7 January 2022 |access-date=12 February 2022}} {{PD-notice}}</ref>

|-

Line 498:

| 27 June 1958

| 27 June 1958

| Energetic particle studies helped confirm the presence of [[Van Allen radiation belt]]<ref>{{citation-attribution|1={{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1958-003A |title=Explorer 3 (1958-003A) |publisher=NASA |date=7 January 2022 |access-date=12 February 2022}} {{PD-notice}}</ref>

|-

! 4

| [[Explorer 4]]

| July 26, July 1958

| [[Juno I]]

| 26

| MEO

| October 5, October 1958

| October 23, October 1959

| Monitor charged particles inside Van Allen belts from nuclear detonations (during [[Operation Argus]])<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1958-005A |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |access-date=2018-04-20}} {{PD-notice}}</ref>

|- style="background:#fbb;"

! style="background:#fbb;"| 5

| [[Explorer 5]]

| August 24, August 1958

| [[Juno I]]

| 17

Line 520:

| —

| —

| Planned in conjunction with Explorer 4, but launch failed<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=EXPLR5 |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |access-date=2018-04-20}} {{PD-notice}}</ref>

|- style="background:#fbb;"

! style="background:#fbb;"| —

| [[Explorer S-1]] (7X)

| July 16, July 1959

| [[Juno II]]

| 42

Line 531:

| —

| —

| Planned to measure Earth's radiation balance, but destroyed within seconds by range safety<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=EXP-7X |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |access-date=2018-04-20}} {{PD-notice}</ref>

|-

! 6

| [[Explorer 6]] (S-2, Able 3)

| August 7, August 1959

| [[Thor-Able]]

| 64

| HEO

| October 6, October 1959

| July12 1,July 1961

| Magnetosphere research and digital telemetry; first NASA launch, first Earth photo from orbit<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1959-004A |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |access-date=2018-04-20}} {{PD-notice}}</ref><ref name="space-timeline">{{cite web |url=https://www.space.com/4422-timeline-50-years-spaceflight.html |title=Timeline: 50 Years of Spaceflight |website=[[Spacespace.com]] |date=28 September 2012 |access-date=24 June 2019}}</ref>

|-

! 7

| [[Explorer 7]] (S-1A)

| October 13, October 1959

| [[Juno II]]

| 42

| LEO

| August 24, August 1961

| In orbit

| Micrometeoroids and energetic particle studies, first satellite to measure Earth's climate<ref>{{cite web |url=https://www.ssec.wisc.edu/media/spotlight/explorer7.html |title=50 Year Anniversary of Explorer 7 Launch |publisher=Ssecssec.wisc.edu |access-date=2018-04-20 |archive-date=10 June 2017 |archive-url=https://web.archive.org/web/20170610094052/http://www.ssec.wisc.edu/media/spotlight/explorer7.html |url-status=dead }}</ref><ref>{{cite web |last=Evans |first=Gareth |url=https://www.aerospace-technology.com/features/feature78185/ |title=Nasa's High-Tech Climate Monitoring |publisher=Aerospace Technology |date=2010-04-05 |access-date=2018-04-20}}</ref><ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1959-009A |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |access-date=2018-04-20 }} {{PD-notice}}</ref>

|- style="background:#fbb;"

! style="background:#fbb;"| –

| S-46A (IE-B)

| March 23, March 1960

| [[Juno II]]

| 16

Line 564:

| —

| —

| Analyze electron and proton radiation energies, failed to achieve orbit<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=EXS-46 |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |date=2017-03-21 |access-date=2018-04-20}} {{PD-notice}}</ref>

|-

Line 575:

| 27 December 1960

| 27 March 2012

| Measured atmospheric composition of the ionosphere<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1960-014A |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |access-date=2018-04-20}} {{PD-notice}}</ref>

|- style="background:#fbb;"

! style="background:#fbb;"| –

| [[S-56 (satellite)|S-56]]

| December 4, December 1960

| [[Scout X-1]]

| 6

Line 586:

| —

| —

| Atmosphere density measurement, but failed to achieve orbit<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=EXS-56 |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |date=2017-03-21 |access-date=2018-04-20}} {{PD-notice}}</ref>

|-

! 9

| [[Explorer 9]] (S-56A)

| February 16, February 1961

| [[Scout X-1]]

| 36

| LEO

| April 9, April 1964

| April 9, April 1964

| Atmospheric density measurements, first spacecraft placed in orbit by a solid-fuel rocket<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1961-004A |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |access-date=2018-04-20}} {{PD-notice}}</ref>

|- style="background:#fbb;"

! style="background:#fbb;"| –

| [[S-45 (satellite)|S-45]]

| February 24, February 1961

| [[Juno II]]

| 34

Line 608:

| —

| —

| Ionosphere research, but failed to achieve orbit<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=EXS-451 |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |date=2017-03-21 |access-date=2018-04-20}} {{PD-notice}}</ref>

|-

! 10

| [[Explorer 10]] (P 14)

| March 25, March 1961

| [[Delta (rocket family)|Thor-Delta]]

| 79

| HEO

| March 25, March 1961

| June 1, June 1968

| Investigated the magnetic field between the Earth and Moon<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1961-010A |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |date=2017-03-21 |access-date=2018-04-20}} {{PD-notice}}</ref>

|-

Line 630:

| November 17, 1961

| In orbit

| Gamma ray astronomy<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1961-013A |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |date=2017-03-21 |access-date=2018-04-20}} {{PD-notice}}</ref>

|- style="background:#fbb;"

Line 641:

| —

| —

| Ionosphere research, failed to achieve orbit. Last Juno II launch.<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=EXS-452 |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |date=2017-03-21 |access-date=2018-04-20}} {{PD-notice}}</ref>

|- style="background:#fbb;"

Line 652:

| —

| —

| Micrometeoroid research, failed to achieve orbit<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=EXS-55 |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |date=2017-03-21 |access-date=2018-04-20}} {{PD-notice}}</ref>

|-

Line 663:

| December 6, 1961

| September 1, 1963

| Energetic particle research<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1961-020A |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |access-date=2018-04-20}} {{PD-notice}}</ref>

|- style="background: #ffb;"

Line 674:

| August 28, 1961

| August 28, 1961

| Micrometeoroid research; partial failure<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1961-022A |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |access-date=2018-04-20}} {{PD-notice}}</ref>

|-

Line 685:

| August 11, 1963

| July 1, 1966

| Energetic particle research<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1962-051A |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |access-date=2018-04-20}} {{PD-notice}}</ref>

|-

Line 696:

| January 30, 1963

| January 15, 1978

| Energetic particle research<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1962-059A |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |date=2017-03-21 |access-date=2018-04-20}} {{PD-notice}}</ref>

|-

! 16

| S-55B

| December&nbsp; 16, 1962

| [[Scout (rocket)|Scout X-3]]

| 101

Line 707:

| July 22, 1963

| In orbit

| Micrometeoroid research<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1962-070A |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |access-date=2018-04-20}} {{PD-notice}}</ref>

|-

Line 718:

| July 10, 1963

| November 24, 1966

| Atmospheric research<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1963-009A |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |access-date=2018-04-20}} {{PD-notice}}</ref>

|-

Line 729:

| May 10, 1965

| December 30, 1965

| Magnetospheric research<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1963-046A |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |access-date=2018-04-20}} {{PD-notice}}</ref>

|-

Line 740:

| May 10, 1981

| May 10, 1981

| Atmospheric density measurements<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1963-053A |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |date=2017-03-21 |access-date=2018-04-20}} {{PD-notice}}</ref>

|- style="background:#fbb;"

Line 751:

| —

| —

| Launch failure<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=EXS-66A |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |date=2017-03-21 |access-date=2018-04-20}} {{PD-notice}}</ref>

|-

Line 762:

| December 29, 1965

| In orbit

| Ionosphere research<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1964-051A |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |access-date=2018-04-20}} {{PD-notice}}</ref>

|-

Line 773:

| October 13, 1965

| January 30, 1966

| Magnetospheric research<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1964-060A |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |access-date=2018-04-20}} {{PD-notice}}</ref>

|-

Line 784:

| February 1970

| In orbit

| Ionospheric and geodetic research<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1964-064A |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |date=2017-03-21 |access-date=2018-04-20}} {{PD-notice}}</ref>

|-

Line 795:

| November 7, 1965

| June 29, 1983

| Micrometeoric research<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1964-074A |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |access-date=2018-04-20}} {{PD-notice}}</ref>

|-

Line 806:

| October 18, 1968

| October 18, 1968

| Atmospheric density measurements<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1964-076A |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |access-date=2018-04-20}} {{PD-notice}}</ref>

|-

Line 817:

| December 1966

| In orbit

| Ionospheric research<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1964-076B |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |date=2017-03-21 |access-date=2018-04-20}} {{PD-notice}}</ref>

|-

Line 828:

| December 27, 1967

| August 23, 2021

| High energy particle observations<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1964-086A |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |access-date=2018-04-20}} {{PD-notice}}</ref>

|-

Line 839:

| July 20, 1973

| In orbit

| Magnetospheric research<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1965-032A |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |access-date=2018-04-20}} {{PD-notice}}</ref>

|-

Line 850:

| May 12, 1967

| July 4, 1968

| Magnetospheric research<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1965-042A |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |access-date=2018-04-20}} {{PD-notice}}</ref>

|-

Line 861:

| June 23, 1978

| In orbit

| Geodetic Earth monitoring<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1965-089A |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |date=2017-03-21 |access-date=2018-04-20}} {{PD-notice}}</ref>

|-

Line 867:

| [[Solrad 8|SOLRAD 8]] (SE-A)

| November 19, 1965

| [[Scout (rocket family)|Scout X-4]]

| 57

| LEO

| November 5, 1967

| In orbit

| Solar radiation monitoring (Cover for covert [[Signals intelligence|ELINT]] mission)<ref>{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1965-093A |title=NASA - NSSDCA - Spacecraft - Details |publisher=National Space Science Data Center |access-date=2018-04-20}} {{PD-notice}}</ref>

|-