Editing Ranger 4 (section)

==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>