Editing Ranger 4

{{Short description|1962 American unmanned space flight intended to study the Moon}}
{{Infobox spaceflight
| name                  = Ranger 4
| image                 = 1964 71394L.jpg
| image_size            =240
| image_caption         = Ranger 4
| mission_type          = [[Moon|Lunar]] impactor
| operator              = [[NASA]]
| Harvard_designation   = 1962 Mu 1
| COSPAR_ID             = 1962-012A
| SATCAT                = 280
| mission_duration      = {{nowrap|10 hours <small>(operational)</small>}}<br/>64 hours <small>(to impact)</small>

| spacecraft_type       = 
| manufacturer          = [[Jet Propulsion Laboratory]]
| dry_mass              = 
| launch_mass           = {{convert|331.1|kg|lb|abbr=on}}
| dimensions            = {{convert|1.52|x|2.51|m|ft|abbr=on}}
| power                 = 135 W

| launch_date           = {{start-date|April 23, 1962, 20:50:00|timezone=yes}}&nbsp;UTC
| launch_rocket         = [[Atlas-Agena|Atlas LV-3 Agena-B]]   
| launch_site           = [[Cape Canaveral Air Force Station|Cape Canaveral]] [[Cape Canaveral Air Force Station Launch Complex 12|LC-12]]
| launch_contractor     =

| orbit_epoch           = 
| orbit_reference       = <!--transfer orbit-->
| orbit_periapsis       = 
| orbit_apoapsis        = 
| orbit_inclination     = 
| apsis                 =

|interplanetary         = 
 {{Infobox spaceflight/IP
   |type                = impactor
   |object              = [[Moon|Lunar]]
   |arrival_date        = {{end-date|April 26, 1962, 12:49:53|timezone=yes}}&nbsp;UTC<br/><small>Failed before impact</small>
   |location            = {{Lunar coords and quad cat|15.5|S|130.7|W}}
 }}

| instruments_list      = 
{{Infobox spaceflight/Instruments
  |name1  = [[Television camera]]<ref name="nssdc instruments">{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/displayExperiment.action?spacecraftId=1962-012A |title=Experiments on Ranger 4 |work=NSSDC Master Catalog |first=Goddard Space Flight Center |last=NASA |access-date=December 3, 2022}}</ref>
  |name2  = [[Gamma ray]] [[spectrometer]]
  |name3  = [[Radar]] [[altimeter]]
  |name4  = [[Seismometer]]
}}

| programme             = ''[[Ranger program|Ranger]]''
| previous_mission      = [[Ranger 3]]
| next_mission          = [[Ranger 5]]
}}

'''Ranger 4''' was a spacecraft of the [[Ranger program]], launched in 1962. It was designed to transmit pictures of the lunar surface to [[Earth]] stations during a period of 10 minutes of flight prior to crashing upon the [[Moon]], to rough-land a [[seismometer]] capsule on the Moon, to collect [[gamma-ray]] data in flight, to study radar reflectivity of the lunar surface, and to continue testing of the Ranger program for development of lunar and interplanetary spacecraft.

An onboard computer failure caused failure of the deployment of the [[Photovoltaic module|solar panel]]s and navigation systems; as a result the spacecraft crashed on the [[Far side (Moon)|far side]] of the Moon without returning any scientific data. It was the first spacecraft of the [[United States]] to reach another [[celestial body]]<ref name="nssdc1962-012A" >{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1962-012A|title=National Space Science Data Center - Ranger 4|publisher=National Air and Space Administration|access-date=19 June 2012|ref=nssdc1962-012A}}</ref><ref name=lmtapcomn>{{cite news |url=https://news.google.com/newspapers?id=Tr5eAAAAIBAJ&sjid=LTEMAAAAIBAJ&pg=3056%2C4113998 |work=Lewiston Morning Tribune |location=(Idaho) |agency=Associated Press |title=Ranger 4 crashes on Moon |date=April 27, 1962 |page=1}}</ref><ref name=bbupinstr>{{cite news |url=https://news.google.com/newspapers?id=zussAAAAIBAJ&sjid=k_kDAAAAIBAJ&pg=2530%2C613084 |work=Bend Bulletin |location=(Oregon) |agency=UPI |title=Ranger-4 hits moon in new space triumph |date=April 26, 1962 |page=1}}</ref> and the first of any nation to reach the surface of the far side of the Moon.

==Spacecraft design==
[[File:Atlas Agena B with Ranger 4 (Apr. 23, 1962).png|thumb|left|100px|Launch of Ranger 4]]

Ranger 4 was a Block II Ranger spacecraft virtually identical to [[Ranger 3]]. The basic vehicle was {{convert|331|kg|abbr=on}}, {{convert|3.1|m|abbr=on}} high and consisted of a lunar capsule covered with a balsawood impact-limiter, {{convert|0.65|m|in|abbr=on}} in diameter, a mono-propellant mid-course motor, a {{convert|22.6|kN|lb-f|-1|abbr=on}} thrust retrorocket, and a gold- and chrome-plated hexagonal base {{convert|1.5|m|abbr=on}} in diameter. A large high-gain dish antenna was attached to the base. Two wing-like solar panels ({{convert|5.2|m|abbr=on}} across) were attached to the base and deployed early in the flight.

Power was generated by 8,680 solar cells contained in the solar panels which charged an {{convert|11.5|kg|abbr=on}} 1&nbsp;kWh capacity [[Silver zinc battery|AgZn]] launching and backup battery. Spacecraft control was provided by a solid-state computer and sequencer and an Earth-controlled command system. Attitude control was provided by [[Sun]] and [[Earth]] sensors, [[gyroscope]]s, and pitch and roll jets. The telemetry system aboard the spacecraft, consisting of two 960&nbsp;[[Megahertz|MHz]] transmitters, one at 3&nbsp;[[Watt (unit)|W]] power output and the other at 50&nbsp;mW power output, the [[high-gain antenna]], and an omnidirectional antenna. White paint, gold and chrome plating, and a silvered plastic sheet encasing the retrorocket furnished thermal control.<ref name="nssdc1962-012A" />

Because heat sterilization was suspected to have caused the malfunction of [[Ranger 3]]'s computer, this procedure was dropped on Ranger 4. The seismometer capsule was also painted with a sawtooth pattern for better thermal protection.<ref name="nssdc1962-012A" />

The experimental apparatus included: (1) a vidicon television camera, which employed a scan mechanism that yielded one complete frame in ten seconds; 2) a gamma-ray spectrometer mounted on a {{convert|1.8|m|abbr=on}} boom; (3) a radar altimeter; and (4) a seismometer to be rough-landed on the lunar surface. The seismometer was encased in the lunar capsule along with an amplifier, a 50-milliwatt transmitter, voltage control, a [[turnstile antenna]], and six [[Silver-cadmium battery|silver-cadmium batteries]] capable of operating the lunar capsule transmitter for 30 days, all designed to land on the Moon at {{convert|130|to|160|km/h|mph|round=5|abbr=on}}. The radar altimeter would be used for reflectivity studies, but was also designed to initiate capsule separation and ignite the retro-rocket.<ref name="nssdc1962-012A" />

==Mission==
Atlas 133D and Agena 6004 arrived at [[Cape Canaveral Air Force Station|Cape Canaveral]] in March and began preflight checkouts. Unlike with previous Ranger launches, no serious difficulties were encountered in readying the launch vehicle for flight and the probe also passed all systems tests with ease. On April 20, Ranger 4 was stacked atop the booster and liftoff took place at 3:50 pm [[Eastern Time Zone|EST]] on April 23.<ref name=tumisp>{{cite news |url=https://news.google.com/newspapers?id=Wz0yAAAAIBAJ&sjid=O-UFAAAAIBAJ&pg=6258%2C1726822 |work=Lawrence Daily Journal-World |location=(Kansas) |agency=Associated Press |title='Brainless' Ranger tumbles into space |date=April 24, 1962 |page=1}}</ref><ref name=bbupsxty>{{cite news |url=https://news.google.com/newspapers?id=--ssAAAAIBAJ&sjid=k_kDAAAAIBAJ&pg=1989%2C451517 |work=Bend Bulletin |location=(Oregon) |agency=UPI |title=Ranger 4 shot starts 60-hr trip |date=April 23, 1962 |page=1}}</ref> Launch proceeded perfectly this time and there were no anomalies with either the Atlas or the Agena, which performed its second burn to send Ranger 4 on a [[Trans-lunar injection|translunar]] trajectory.

After separation from the Agena, it was apparent that something was seriously amiss when tracking stations picked up Ranger 4's radio transmitter, but there was no [[telemetry]] data being returned or any response when commands were sent to the computer. Without [[telemetry]], it could not be confirmed that the probe's solar panels had unfolded, but the fluctuating radio [[transponder]] indicated that Ranger 4 was tumbling and that the solar panels and high-gain antenna were not deployed either.

The [[Atlas-Agena|Atlas and Agena]] had both performed perfectly, in fact so well that Ranger 4 would not even need a midcourse correction burn to impact the Moon. However, this was all futile if the spacecraft was inoperative. Ground controllers sent commands to the probe to unfurl the solar panels and high-gain antenna and manually use the attitude control system to stop the rolling motion it was in, but the probe was unresponsive. The Spacecraft Data Analysis Team at [[Jet Propulsion Laboratory|JPL]] concluded that the main timer in Ranger 4's computer had stopped, which disabled the telemetry system, preprogrammed events such as [[solar panel]] deployment, and also made the probe completely unresponsive to manual commands. Even though lunar impact would occur as planned, the mission was for all intents and purposes a failure. Making it a more bitter pill to swallow was the nearly-flawless launch vehicle performance. The booster problems that affected [[Ranger program|Rangers 1-3]] had been resolved, only for the probe itself to completely fail, as unlike the previous missions, Ranger 4 did not return any useful data. Finding the cause of the timer malfunction could also be difficult since it had occurred during the coasting phase prior to trans-lunar injection when Ranger 4 was passing between tracking stations in the [[Caribbean]] and [[South Africa]].

Without solar power, Ranger 4's batteries ran down on the morning of April 26 and the radio transponder ceased operating. The tiny transmitter in the seismometer capsule continued sending out a 50-milliwatt signal. According to the NASA, Ranger 4 impacted the far side of the [[Moon]] (229.3 degrees E, 15.5 degrees S) at {{convert|9600|km/h|-1|abbr=on}} at 12:49:53 [[Universal Time|UT]] on April 26, 1962, after 64 hours of flight.<ref name="nssdc1962-012A" /><ref name=lmtapcomn/><ref name=bbupinstr/> However, the coordinates were ″guesstimated" and the crater of the impact could not be identified by high-resolution images of the [[Lunar Reconnaissance Orbiter]].<ref>{{Cite web |url=https://www.leonarddavid.com/farside-science-the-saga-of-ranger-4s-moon-journey/ |title=Farside Science: The Sage of Ranger 4's Moon Journey |date=2018-12-30 |access-date=2023-01-02 |last=Leonard |first=David}}</ref>

[[NASA]] officials tried to put a positive spin on the mission,<ref name=bbupinstr/> noting that it was the first time an [[United States|American]] spacecraft had reached the surface of the Moon and that the probe was "far more sophisticated" than the [[Soviet Union|Soviet]] [[Luna 2]] space probe in 1959, which had been little more than a pressurized sphere designed to deposit pennants on the surface at impact. The excellent performance of the Atlas-Agena booster had also raised morale.

This spacecraft, similar in design to [[Ranger 3]], was the first American spacecraft to reach another celestial body. It was also the first spacecraft to impact the far side of the Moon. Although the spacecraft did not achieve its primary objective, the Atlas-Agena-Ranger combination performed without fault for the first time.<ref>{{cite journal |title=Discussion |journal=Space Policy |volume=14 |issue=1 |year=1998 |pages=5–8 |doi=10.1016/S0265-9646(97)00038-6 |bibcode=1998SpPol..14....5. }}</ref>

==See also==
{{Portal|Solar System|Spaceflight}}
* [[Ranger program]]
* [[Timeline of Solar System exploration]]
* [[List of artificial objects on the Moon]]
* [[List of missions to the Moon]]

==References==
{{reflist|2}}

==External links==
*[https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19780007206_1978007206.pdf Lunar impact: A history of Project Ranger (PDF) 1977]
*[https://web.archive.org/web/20081023030128/http://in.reuters.com/article/topNews/idINIndia-36091120081022 Reuters.com], Planned lunar missions
*[https://web.archive.org/web/20081023030123/http://in.reuters.com/article/topNews/idINIndia-36089520081022 Reuters.com], Chronology – Five key dates in the race to the Moon

{{Ranger program | before=[[Ranger 3]] | after=[[Ranger 5]] }}
{{Moon spacecraft}}
{{Orbital launches in 1962}}
{{NASA space program}}

{{Use American English|date=January 2014}}

[[Category:Ranger program|4]]
[[Category:Spacecraft launched in 1962]]
[[Category:Spacecraft that impacted the Moon]]
[[Category:1962 on the Moon]]