Editing Vanguard 1

{{Short description|American satellite launched in 1958; oldest manmade object currently in Earth orbit}}
{{Use American English|date=January 2021}}
{{Use dmy dates|date=January 2021}}
{{Infobox spaceflight
| name               = Vanguard 1
| names_list         = Vanguard TV-4<br/>Vanguard Test Vehicle-Four
| image              = Vanguard_1.jpg
| image_caption      = A model of Vanguard 1
| image_size         = 300px
| mission_type       = [[Earth science]]
| operator           = [[United States Naval Research Laboratory|Naval Research Laboratory]]
| Harvard_designation = 1958-Beta 2<ref name="Display"/>
| COSPAR_ID          = 1958-002B
| SATCAT             = 00005
| mission_duration   = 90 days (planned) <br/>  {{time interval|17 March 1958|show=ymd}} <br/> (in orbit)
| spacecraft         = Vanguard 1
| spacecraft_type    = [[Project Vanguard|Vanguard]]
| manufacturer       = [[United States Naval Research Laboratory|Naval Research Laboratory]]
| launch_mass        = {{cvt|1.46|kg}}
| dimensions         = {{cvt|152|mm}} diameter, {{cvt|3.0|ft}} antenna span
| power              = <!-- [[watt]]s -->
| launch_date        = 17 March 1958, 12:15:41 [[Greenwich Mean Time|GMT]]
| launch_rocket      = [[Vanguard (rocket)|Vanguard TV-4]]
| launch_site        = [[Cape Canaveral Space Force Station|Cape Canaveral]], [[Cape Canaveral Launch Complex 18|LC-18A]]
| launch_contractor  = [[Glenn L. Martin Company]]
| last_contact       = May 1964
| decay_date         = 2198 (estimated)<br/>~ 240 years orbital lifetime<ref name="Display"/>
| orbit_reference    = [[Geocentric orbit]]<ref name="n2yo">{{cite web|url=http://www.n2yo.com/satellite/?s=00005|title=Vanguard 1 Satellite details 1958-002B NORAD 00005|publisher=N2YO|access-date=1 February 2021}}</ref>
| orbit_regime       = [[Medium Earth orbit]]
| orbit_periapsis    = {{cvt|654|km}}
| orbit_apoapsis     = {{cvt|3969|km}}
| orbit_inclination  = 34.25°
| orbit_period       = 134.27 minutes
| apsis              = gee
| instruments        = 
| programme          = [[Project Vanguard]]
| previous_mission   = [[Vanguard TV-3BU]]
| next_mission       = [[Vanguard TV-5]]
}}

'''Vanguard 1''' (Harvard designation: '''1958-Beta 2''',<ref name="US Space Objects Registry">{{cite web|title=U.S. Space Objects Registry|url=https://usspaceobjectsregistry.state.gov/Pages/Search.aspx|access-date=2009-06-25|url-status=dead|archive-url=https://web.archive.org/web/20131006073413/https://usspaceobjectsregistry.state.gov/Pages/Search.aspx|archive-date=2013-10-06}} {{PD-notice}}</ref> [[International Designator|COSPAR ID]]: '''1958-002B'''<ref name="Display">{{cite web|date=14 May 2020|title=Display: Vanguard 1 1958-002B|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1958-002B|access-date=1 February 2021|publisher=NASA}} {{PD-notice}}</ref>) is an American [[satellite]] that was the fourth artificial [[Geocentric orbit|Earth-orbiting]] satellite to be successfully launched, following [[Sputnik 1]], [[Sputnik 2]], and [[Explorer 1]]. It was launched 17 March 1958. Vanguard 1 was the first satellite to have [[solar power|solar electric power]].<ref name="NRL">{{cite web |url=http://code8100.nrl.navy.mil/about/heritage/vanguard.htm |title=Vanguard I The World's Oldest Satellite Still in Orbit |archive-url=https://web.archive.org/web/20150321054447/http://code8100.nrl.navy.mil/about/heritage/vanguard.htm |archive-date=2015-03-21|access-date=September 24, 2007}} {{PD-notice}}</ref> Although communications with the satellite were lost in 1964, it remains the oldest man-made object still in orbit, together with the upper stage of its launch vehicle.<ref name="Display"/>

Vanguard 1 was designed to test the launch capabilities of a three-stage [[launch vehicle]] as a part of [[Project Vanguard]], and the effects of the [[space environment]] on a satellite and its systems in [[Earth]] orbit. It also was used to obtain [[geodesy|geodetic]] measurements through orbit analysis.<ref>{{cite journal |first1=J. A. |last1=O'Keefe |first2=Ann |last2=Eckeis |first3=R. K. |last3=Squires |year=1959 |title=Vanguard Measurements Give Pear-Shaped Component of Earth's Figure |url=https://www.science.org/doi/10.1126/science.129.3348.565 |journal=Science |volume=129 |doi=10.1126/science.129.3348.565 |pages=565–566 |issue=3348}}</ref> Vanguard 1, being small and light enough to carry with one hand, was described by the [[Soviet Premier]], [[Nikita Khrushchev]], as "the [[grapefruit]] satellite".<ref>{{cite web|url=http://code8200.nrl.navy.mil/vanguard.html|title=Vanguard I – The World's Oldest Satellite Still in Orbit|publisher=Spacecraft Engineering Department, U.S. Navy|url-status=dead|archive-url= https://web.archive.org/web/20080919152144/http://code8200.nrl.navy.mil/vanguard.html|archive-date=2008-09-19}} {{PD-notice}}</ref>

== Spacecraft design ==
The spacecraft is a {{cvt|1.46|kg}} [[Aluminium|aluminum]] [[sphere]] {{convert|6|in|mm|spell=in}} in diameter, with antennas spanning {{convert|3|ft|m|spell=in}}. It contains a 10 [[Watt|mW]], 108 [[Hertz|MHz]] transmitter powered by a [[mercury battery]] and a 5&nbsp;mW, 108.03&nbsp;MHz transmitter that was powered by six [[solar cell]]s mounted on the body of the satellite.<ref>{{cite web|url=http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=AD0419878|title=Project Vanguard Report No. 23 Minitrack Report No. 3, Receiver System|publisher=dtic.mil|url-status=dead|archive-url=https://web.archive.org/web/20110823131330/http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=AD0419878|archive-date=2011-08-23}} {{PD-notice}}</ref> Six {{cvt|30|cm}} long [[Antenna (radio)|antennas]], {{cvt|0.8|cm}} diameter spring-actuated aluminum alloy aerials protrude from the sphere. The transmitters were used primarily for engineering and tracking data, but were also used to determine the [[total electron content]] between the satellite and the ground stations.<ref name="Display"/>

A backup version of Vanguard 1 is on display at the [[National Air and Space Museum|Smithsonian National Air and Space Museum]], [[Steven F. Udvar-Hazy Center]] in [[Chantilly, Virginia]].<ref name=udvarbackup>
{{cite web|url=https://airandspace.si.edu/collection-objects/satellite-vanguard-1-backup|title=Satellite Vanguard 1 Backup|website=airandspace.si.edu|publisher=Steven F. Udvar-Hazy Center|access-date=19 March 2018|url-status=live|archive-url=https://web.archive.org/web/20180205130200/https://airandspace.si.edu/collection-objects/satellite-vanguard-1-backup|archive-date=5 February 2018}} {{PD-notice}}</ref>

== Mission ==
[[File:1958-03-17 3rd Vanguard Successful.webm|thumb|upright=1.2|right|thumbtime=11|[[Universal Newsreel]] about the launch of Vanguard 1]]On 17 March 1958, the three-stage launch vehicle placed Vanguard into a {{cvt|654|x|3969|km|mi}}, 134.27-minute elliptical orbit [[Orbital inclination|inclined]] at 34.25°. Original estimates had the orbit lasting for 2,000 years, but it was discovered that solar [[radiation pressure]] and [[atmospheric drag]] during high levels of solar activity produced significant perturbations in the [[Apsis|perigee]] height of the satellite, which caused a significant decrease in its expected lifetime to about 240 years.<ref name="Display" /> Vanguard 1 transmitted its signals for over six years as it orbited the Earth.<ref name="NTRS">{{cite journal|last=Rosenthal|first=Alfred|title=A record of NASA space missions since 1958|url=http://hdl.handle.net/2060/19940003358|publisher=NASA|journal=NASA Technical Reports Server|date=January 1982 |hdl=2060/19940003358|access-date=24 September 2011}}</ref>

=== Radio beacon ===
A 10&nbsp;mW [[Mercury battery|mercury-battery]]-powered telemetry transmitter on the 108&nbsp;MHz band used for [[International Geophysical Year]] (IGY) scientific satellites, and a 5&nbsp;mW, 108.03&nbsp;MHz [[Minitrack]] transmitter powered by six [[solar cell]]s were used as part of a radio phase-comparison angle-tracking system. The system transmitted signals through the satellite's six spring-loaded aluminum alloy aerials. Satellite tracking was achieved using these transmitters and Minitrack ground stations situated around the globe.<ref name="Experiment1"/>

These radio signals were used to determine the [[total electron content]] between the satellite and selected ground-receiving stations. The battery-powered transmitter provided internal package temperature for about 16 days and sent tracking signals for 20 days. The solar-cell-powered transmitter operated for more than six years. Signals gradually weakened and were last received at the [[Minitrack|Minitrack station]] in [[Quito]], [[Ecuador]], in May 1964. Since then the spacecraft has been tracked optically from Earth, via [[telescope]].<ref name="Experiment1">{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1958-002B-01|title=Radio Beacon|publisher=NASA|date=14 May 2020|access-date=1 February 2021}} {{PD-notice}}</ref>

=== Design for atmospheric density measurements ===
Because of its symmetrical shape, Vanguard 1 was used by experimenters for determining upper atmospheric densities as a function of [[altitude]], [[latitude]], [[season]], and [[Solar phenomena|solar activity]]. As the satellite continuously orbited, it would deviate from its predicted positions slightly, accumulating greater and greater shift due to drag of the residual atmosphere. By measuring the rate and timing of orbital shifts, together with the body's drag properties, the relevant atmosphere's parameters could be back-calculated. It was determined that atmospheric pressures, and thus drag and orbital decay, were higher than anticipated, since Earth's upper atmosphere does taper off into space gradually.<ref name="Experiment2">{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1958-002B-02|title=Satellite Drag Atmospheric Density|publisher=NASA|date=14 May 2020|access-date=1 February 2021}} {{PD-notice}}</ref>

This experiment was planned extensively prior to launch. Initial [[United States Naval Research Laboratory|Naval Research Laboratory]] (NRL) proposals for the project included conical satellite bodies; this eliminated the need for a separate fairing and ejection mechanisms, and their associated weight and [[separation event|failure modes]]. Radio-tracking would gather data and establish a position. Early in the program, optical tracking (with a [[Schmidt camera|Baker-Nunn camera]] network and [[Operation Moonwatch|human spotters]]) was added. A panel of scientists proposed changing the design to spheres, at least {{cvt|50.8|cm}} in diameter and hopefully {{cvt|76.2|cm}}. 

A sphere would have a constant optical reflection, and constant [[Drag coefficient|coefficient of drag]], based on size alone, while a cone would have properties that varied with its orientation. [[James Van Allen]] of the [[University of Iowa]] proposed a cylindrical satellite based on his work with [[rockoon]]s, which became [[Explorer 1]], the first American satellite. The Naval Research Laboratory finally accepted a sphere with a {{cvt|16.5|cm}} of diameter as a "Test Vehicle", with a diameter of {{cvt|50.8|cm}} set for the follow-on satellites. The weight savings, from reduced size as well as decreased instrumentation in the early satellites, was considered to be acceptable.

As Vanguard 1, [[Vanguard 2]], and [[Vanguard 3]] are still orbiting with their drag properties essentially unchanged, they form a baseline data set on the [[atmosphere of Earth]] that is over 60 years old and continuing.

== After the mission ==
[[File:Vanguard 1 satellite sketch.png|thumb|upright=1.2|right|Vanguard 1 satellite sketch]]

After its scientific mission ended in 1964, Vanguard 1 became a [[:Category:Derelict satellites orbiting Earth|derelict]] [[space debris|object]] – as did the upper stage of the launch rocket, after it finished the [[delta-v]] maneuver to place Vanguard 1 in orbit in 1958. Both objects remain in orbit. Vanguard 1 was projected to remain aloft for up to 2,000 years, but solar radiation pressure and atmospheric drag perturbations during periods of high solar activity affected its perigee, reducing its lifetime, and now it is expected to burn up in the atmosphere in about 240 years, sometime in the late 22nd century. As space travel becomes routine, and especially when its re-entry date draws near, some have suggested that the satellite might be retrieved as a valued artifact of early space exploration.<ref> https://pages.vassar.edu/realarchaeology/2023/12/03/a-closer-look-at-the-archaeological-importance-of-the-vanguard-1/ </ref>

=== 50th anniversary ===
The Vanguard 1 satellite and upper launch stage hold the record for being in space longer than any other human-made object,<ref>{{cite web|url=http://www.bbc.com/future/story/20171005-the-worlds-oldest-scientific-satellite-is-still-in-orbit|title=The world's oldest scientific satellite is still in orbit|first=Richard|last=Hollingham|publisher= BBC Future|date=2017-10-06|url-status=live|archive-url=https://web.archive.org/web/20171007230117/http://www.bbc.com/future/story/20171005-the-worlds-oldest-scientific-satellite-is-still-in-orbit|archive-date=2017-10-07}}</ref><ref name="Erickson2010">{{cite book|author=Lance K. Erickson|title=Space Flight: History, Technology, and Operations|url=https://books.google.com/books?id=dr6R51cqQ6IC&pg=PA60|year=2010|publisher=Rowman & Littlefield|isbn=978-0-86587-419-0|pages=60–}}</ref> and as such have traveled farther over the Earth's surface than any other human-made object.<ref>{{cite web|url=https://what-if.xkcd.com/86/|title=Far-Traveling Objects|website=what-if.xkcd.com|access-date=2019-05-16}}</ref>

A small group of former [[United States Naval Research Laboratory|NRL]] and [[NASA]] workers had been in communication with one another, and a number of government agencies were asked to commemorate the event. The Naval Research Laboratory commemorated the event with a day-long meeting at NRL on 17 March 2008.<ref name="anniversary">{{cite web|url=http://www.eurekalert.org/pub_releases/2008-03/nrl-vic031308.php |title=Vanguard I celebrates 50 years in space|date=13 March 2008|work=EurekAlert!|url-status=live|archive-url=https://web.archive.org/web/20130605153254/http://www.eurekalert.org/pub_releases/2008-03/nrl-vic031308.php|archive-date=5 June 2013}}</ref> The meeting concluded with a simulation of the satellite's track as it passed into the orbital area visible from [[Washington, D.C.]], (where it is visible from the Earth's surface). The [[United States National Academy of Sciences|National Academy of Sciences]] scheduled seminars to mark the 50th anniversary of the [[International Geophysical Year]].<ref name="commemoration ">[http://www.spaceref.com/news/viewnews.html?id=1241 Vanguard Approaches Half A Century In Space], SpaceRef Interactive, by Keith Cowing, November 4, 2007</ref>

== See also ==
{{Portal|Spaceflight}}
* [[Timeline of artificial satellites and space probes]]

== References ==
{{Reflist|30em}}

== External links ==
* [https://www.youtube.com/watch?v=vQuQwDT0eVI  ''United States Space Program Progress 1958''] discusses Vanguard 1 and other American space launches in 1958 at YouTube

{{Project Vanguard}}
{{Orbital launches in 1958}}

[[Category:Spacecraft launched in 1958]]
[[Category:1958 in the United States]]
[[Category:Project Vanguard]]
[[Category:Derelict satellites orbiting Earth]]
[[Category:Gravimetry satellites]]
[[Category:Atmospheric sounding satellites]]
[[Category:Geospace monitoring satellites]]