Editing Explorers Program (section)

=== Continuation of the Explorers Program ===
With the establishment of NASA in 1958, the Explorers 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>{{cite web |url=https://www.nasa.gov/content/goddard-missions-past |title=Goddard Missions |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">{{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 (237-242) |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">{{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"/>
{| class="wikitable sortable"
|+List of [[Interplanetary Monitoring Platform]] (IMP) missions
! rowspan="2" |Mission
! rowspan="2" |Photo
! colspan="2" |Satellite
! rowspan="2" |Launch date
! rowspan="2" |Decay date
! rowspan="2" |Notes
|-
!Explorer
!IMP
|-
|[[Explorer 18|IMP-1]]
|[[File:Explorer-18_IMP-A.jpg|frameless|180x180px]]
|Explorer 18
|IMP-A
|27 November 1963, 02:30 UTC<ref name="jonathan">{{cite web |last=McDowell |first=Jonathan |title=Launch Log |url=http://www.planet4589.org/space/log/launchlog.txt |access-date=2018-06-24 |work=Jonathan's Space Page}}</ref>
|December 30, 1965
|First use of [[integrated circuit]]s in a spacecraft. First satellite in IMP-A/-B/-C design series.
|-
|[[Explorer 21|IMP-2]]
|[[File:Explorer-21 image.jpg|frameless|180x180px]]
|Explorer 21
|IMP-B
|4 October 1964, 03:45 UTC<ref name="jonathan" />
|January 1, 1966
|Second satellite in IMP-A/-B/-C design series.
|-
|[[Explorer 28|IMP-3]]
|[[File:Explorer 28.jpg|frameless|180x180px]]
|Explorer 28
|IMP-C
|29 May 1965, 12:00 UTC<ref name="jonathan" />
|4 July 1968
|Third satellite in IMP-A/-B/-C design series.
|-
|[[Explorer 33|AIMP-1]]
|[[File:IMP-D.jpg|frameless|180x180px]]
|Explorer 33
|IMP-D
|1 July 1966, 16:02 UTC<ref name="jonathan" />
|In orbit
|First use of [[MOSFET]] integrated circuits in a spacecraft, similar design to IMP-E. Originally intended to orbit the Moon, but placed in an elliptical high orbit instead.
|-
|[[Explorer 34|IMP-4]]
|[[File:Explorer 34.jpg|frameless|180x180px]]
|Explorer 34
|IMP-F
|24 May 1967, 14:05 UTC<ref name="jonathan" />
|May 3, 1969
|Similar design to IMP-G.
|-
|[[Explorer 35|AIMP-2]]
|[[File:IMP-E.jpg|frameless|180x180px]]
|Explorer 35
|IMP-E
|19 July 1967, 14:19 UTC<ref name="jonathan" />
|After June 24, 1973
|Similar design to IMP-D. Positioned in [[Moon|Selenocentric orbit]].
|-
|[[Explorer 41|IMP-5]]
|[[File:Explorer-41 IMP-G.jpg|frameless|180x180px]]
|Explorer 41
|IMP-G
|21 June 1969, 08:47 UTC<ref name="jonathan" />
|December 23, 1972
|Similar design to IMP-F.
|-
|[[Explorer 43|IMP-6]]
|[[File:Explorer 43 IMP-I.jpg|frameless|180x180px]]
|Explorer 43
|IMP-I
|13 March 1971, 16:15 UTC<ref name="jonathan" />
|October 2, 1974
|First spacecraft in IMP-I/-H/-J series.
|-
|[[Explorer 47|IMP-7]]
|[[File:Explorer-47 IMP-I.jpg|frameless|180x180px]]
|Explorer 47
|IMP-H
|23 September 1972, 01:20 UTC<ref name="jonathan" />
|In orbit
|Second spacecraft in IMP-I/-H/-J series.
|-
|[[Explorer 50|IMP-8]]
|[[File:IMP_8.gif|frameless|180x180px]]
|Explorer 50
|IMP-J
|26 October 1973, 02:26 UTC<ref name="jonathan" />
|In orbit
|Third spacecraft in IMP-I/-H/-J series, remained in service until 2006
|}
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]].{{citation needed|date=September 2024}}

With decreases in NASA's budget, Explorer missions became infrequent in the early 1980s.{{citation needed|date=September 2024}}