View source for Pioneer 2

{{Short description|Failed NASA mission to the Moon (1958)}}
{{Infobox spaceflight
| name                  = Pioneer 2
| image                 = Pioneer able.png
| image_size            = 300px
| image_caption         = The lunar orbiter Pioneer 2.

| mission_type          = [[Moon|Lunar]] orbiter
| operator              = [[NASA]]
| mission_duration      = {{time interval|8 Nov 1958 07:30:21|8 Nov 1958 08:12:31|show=hms|sep=,}}<br><small>Failed to orbit</small>
| suborbital_apogee     = {{cvt|1550|km|mi}}

| manufacturer          = [[TRW Inc.|Space Technology Laboratories]]
| dry_mass              = 
| launch_mass           = {{cvt|39.2|kg|lb}}{{r|nssdc1|STL-V2}}
| power                 =

| launch_date           = {{start-date|8 November 1958, 07:30:21|timezone=yes}}&nbsp;GMT
| launch_rocket         = [[Thor-Able|Thor DM 18-Able I]]
| launch_site           = [[Cape Canaveral Air Force Station|Cape Canaveral]], [[Cape Canaveral Air Force Station Space Launch Complex 17|LC-17A]]
| launch_contractor     = 

| decay_date            = {{end-date|8 November 1958, 08:12:31|timezone=yes}}&nbsp;GMT<ref name=nasa1/>

| instruments_list      = <!-- start collapsible list of instruments -->
{{Infobox spaceflight/Instruments
  |acronym1  =  | name1  = Ionization Chamber<ref name=nasa1/>
  |acronym2  =  | name2  = Magnetometer
  |acronym3  =  | name3  = Temperature Sensors
  |acronym4  =  | name4  = Micrometeoroid Sensor
  |acronym5  =  | name5  = Proportional Counter Telescope
  |acronym6  =  | name6  = Television System
}}


| programme             = '''[[Pioneer program]]'''
| previous_mission      = [[Pioneer 1]]
| next_mission          = [[Pioneer 3]]
}}

'''Pioneer 2''' (also known as '''Able 3''')<ref name=nasa1/> was the last of the three project [[Pioneer program|Able space probes]] designed to probe [[Moon|lunar]] and [[Wiktionary:cislunar|cislunar]] space. The launch took place at 07:30:21 GMT on 8 November 1958. After Pioneer 1 had failed due to guidance system deficiencies, the guidance system was modified with a Doppler command system to ensure more accurate commands and minimize trajectory errors. Once again, the first and second stage portion of the flight was uneventful,<ref name=STL-V1/> but the third stage of the launch vehicle failed to ignite, making it impossible for Pioneer 2 to achieve orbital velocity. An attempt to fire the vernier engines on the probe was unsuccessful and the [[spacecraft]] attained a maximum altitude of {{convert|1550|km|mi|abbr=on}} before reentering Earth's atmosphere at 28.7° N, 1.9° E over NW Africa.

A small amount of data was obtained during the short flight, including evidence that the equatorial region around Earth has higher flux and higher energy radiation than previously considered and that the micrometeorite density is higher around Earth than in space. The reason for the third stage failure was unclear, but it was suspected that the firing command from the second stage, which contained the guidance package for the entire launch vehicle, was never received, possibly due to damage to electrical lines during staging.

== Spacecraft design ==
[[File:Pioneer I, Reconstructed Replica.jpg|thumb|Reconstructed replica of Pioneer 1, identical to Pioneer 2]]
Pioneer 2 (NSSDCA ID: PION2)<ref name=nssdc1/> was nearly identical to [[Pioneer 1]]. It consisted of a thin cylindrical midsection with a squat truncated [[cone (geometry)|cone]] [[frustum]] on each side. The cylinder was {{convert|74|cm|in|sp=us}} in diameter and the height from the top of one cone to the top of the opposite cone was {{convert|76|cm|in|sp=us}}. Along the axis of the spacecraft and protruding from the end of the lower cone was a {{convert|11|kg|lb|adj=on}} solid [[propellant]] injection rocket and rocket case, which formed the main structural member of the spacecraft. Eight small low-thrust solid propellant velocity adjustment rockets were mounted on the end of the upper cone in a ring assembly which could be jettisoned after use. A magnetic [[dipole antenna]] also protruded from the top of the upper cone. The shell was composed of laminated plastic. The total mass of the spacecraft after vernier separation but before injection rocket firing was {{convert|39.5|kg|lb}}.

The scientific instrument package had a mass of 15.6&nbsp;kg (34.4&nbsp;lb) and consisted of an STL image-scanning television system (which replaced the NOTS (''Naval Ordnance Test Station'') image scanning infrared television system on Pioneer 1), a proportional counter for radiation measurements, an [[ionization chamber]] to measure radiation in space, a diaphragm/microphone assembly to detect micrometeorites, a spin-coil [[magnetometer]] to measure [[magnetic field]]s to 5 microgauss, and temperature-variable resistors to record spacecraft internal conditions. The spacecraft was powered by [[nickel-cadmium battery|nickel-cadmium batteries]] for ignition of the rockets, [[silver-oxide battery|silver cell batteries]] for the television system, and [[mercury battery|mercury batteries]] for the remaining circuits. The radio transmission was at 108.06&nbsp;MHz through a magnetic dipole antenna for the television system, telemetry, and doppler. Ground commands were received at 115&nbsp;MHz. The spacecraft was to be [[spin-stabilized satellite|spin-stabilized]] at 1.8 revolutions per second, the spin direction approximately perpendicular to the [[geomagnetic meridian planes]] of the trajectory.

== References ==
{{reflist|refs=

<ref name="nasa1">{{cite web
| url= https://science.nasa.gov/mission/pioneer-2/
| website= science.nasa.gov
| publisher= [[NASA]]
| title= Pioneer 2 – NASA Science
| date= 14 November 2017
| access-date= 20 February 2021 }}
</ref>

<ref name="nssdc1">{{cite web
| title= Pioneer 2
| url= https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=PION2 
| website= nssdc.gsfc.nasa.gov
| publisher= [[NASA]]
| access-date= 18 August 2023 }}
</ref>

<ref name="STL-V1"> {{cite report
| title= 1958 NASA/USAF Space Probes (ABLE-1) Final Report: Volume 1. Summary 
| date = 18 February 1959
| publisher = [[NASA]] / [[TRW Inc|TRW]]
| url = https://www.sdfo.org/stl/1958%20NASA%20USAF%20Space%20Probes%20%28ABLE-1%29%20FINAL%20REPORT.pdf
| access-date = 17 February 2009
| archive-url= https://web.archive.org/web/20211019050852/https://www.sdfo.org/stl/1958%20NASA%20USAF%20Space%20Probes%20%28ABLE-1%29%20FINAL%20REPORT.pdf
| archive-date= 19 October 2021 }}
</ref>

<ref name="STL-V2">{{cite report
| title= 1958 NASA/USAF Space Probe (ABLE-1) Final Report: Volume 2. Payload and Experiments all
| publisher= [[NASA]] / [[TRW Inc|TRW]]
| url= https://ntrs.nasa.gov/citations/19990008156
| date= 18 February 1959
| access-date= 17 February 2009
| archive-date= 12 April 2022
| archive-url= https://web.archive.org/web/20220412164626/https://ntrs.nasa.gov/citations/19990008156
| url-status = live }}
</ref>

}}

== External links ==
{{Portal|Spaceflight}}
* [https://www.youtube.com/watch?v=vQuQwDT0eVI  ''United States Space Program Progress 1958''] discusses Pioneer 0 - 3 at YouTube
* [http://www.sdfo.org/stl/ Space Technology Laboratories Documents Archive]
* [https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=PION2 NSSDC Master Catalog: Spacecraft ''Pioneer 2'']

{{Pioneer program | before=[[Pioneer 1]] | after=[[Pioneer 3]] }}
{{NASA space program}}
{{Orbital launches in 1958}}

[[Category:Spacecraft launched in 1958]]
[[Category:Missions to the Moon]]
[[Category:Pioneer program|Pioneer 02]]
[[Category:Spacecraft which reentered in 1958]]
[[Category:Space missions that ended in failure]]