Ranger 4 was a spacecraft of the Ranger program, launched in 1962. It was designed to transmit pictures of the lunar surface to

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...

stations during a period of 10 minutes of flight prior to crashing upon the

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

, to rough-land a

seismometer A seismometer is an instrument that responds to ground noises and shaking such as caused by earthquakes, volcanic eruptions, and explosions. They are usually combined with a timing device and a recording device to form a seismograph. The outpu ...

capsule on the Moon, to collect

gamma-ray A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically sh ...

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

solar panel A solar cell panel, solar electric panel, photo-voltaic (PV) module, PV panel or solar panel is an assembly of photovoltaic solar cells mounted in a (usually rectangular) frame, and a neatly organised collection of PV panels is called a photo ...

s and navigation systems; as a result the spacecraft crashed on the

far side ''The Far Side'' is a single-panel comic created by Gary Larson and syndicated by Chronicle Features and then Universal Press Syndicate, which ran from December 31, 1979, to January 1, 1995 (when Larson retired as a cartoonist). Its surrealist ...

of the Moon without returning any scientific data. It was the first spacecraft of the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

to reach another

celestial body An astronomical object, celestial object, stellar object or heavenly body is a naturally occurring physical entity, association, or structure that exists in the observable universe. In astronomy, the terms ''object'' and ''body'' are often us ...

Spacecraft design

Ranger 4 was a Block II Ranger spacecraft virtually identical to

Ranger 3 Ranger 3 was a space exploration mission conducted by NASA to study the Moon. The Ranger 3 robotic spacecraft was launched January 26, 1962 as part of the Ranger program. Due to a series of malfunctions, the spacecraft missed the Moon by and ...

. The basic vehicle was , high and consisted of a lunar capsule covered with a balsawood impact-limiter, in diameter, a mono-propellant mid-course motor, a thrust retrorocket, and a gold- and chrome-plated hexagonal base in diameter. A large high-gain dish antenna was attached to the base. Two wing-like solar panels ( 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 1 kWh capacity 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

sensors,

gyroscope A gyroscope (from Ancient Greek γῦρος ''gŷros'', "round" and σκοπέω ''skopéō'', "to look") is a device used for measuring or maintaining orientation and angular velocity. It is a spinning wheel or disc in which the axis of rot ...

s, and pitch and roll jets. The telemetry system aboard the spacecraft, consisting of two 960 MHz transmitters, one at 3 W power output and the other at 50 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. Because heat sterilization was suspected to have caused the malfunction of

's computer, this procedure was dropped on Ranger 4. The seismometer capsule was also painted with a sawtooth pattern for better thermal protection. 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 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 A turnstile antenna, or crossed-dipole antenna, is a radio antenna consisting of a set of two identical dipole antennas mounted at right angles to each other and fed in phase quadrature; the two currents applied to the dipoles are 90° out of ph ...

, and six silver-cadmium batteries capable of operating the lunar capsule transmitter for 30 days, all designed to land on the Moon at . The radar altimeter would be used for reflectivity studies, but was also designed to initiate capsule separation and ignite the retro-rocket.

Mission

Atlas 133D and Agena 6004 arrived at

Cape Canaveral , image = cape canaveral.jpg , image_size = 300 , caption = View of Cape Canaveral from space in 1991 , map = Florida#USA , map_width = 300 , type = Cape , map_caption = Location in Florida , location ...

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 EST on April 23. 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 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 Telemetry is the in situ collection of measurements or other data at remote points and their automatic transmission to receiving equipment (telecommunication) for monitoring. The word is derived from the Greek roots ''tele'', "remote", an ...

data being returned or any response when commands were sent to the computer. Without

, it could not be confirmed that the probe's solar panels had unfolded, but the fluctuating radio

transponder In telecommunications, a transponder is a device that, upon receiving a signal, emits a different signal in response. The term is a blend of ''transmitter'' and ''responder''. In air navigation or radio frequency identification, a flight trans ...

indicated that Ranger 4 was tumbling and that the solar panels and high-gain antenna were not deployed either. The 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 JPL concluded that the main timer in Ranger 4's computer had stopped, which disabled the telemetry system, preprogrammed events such as

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 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 The Caribbean (, ) ( es, El Caribe; french: la Caraïbe; ht, Karayib; nl, De Caraïben) is a region of the Americas that consists of the Caribbean Sea, its islands (some surrounded by the Caribbean Sea and some bordering both the Caribbean ...

and

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring coun ...

. 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. Ranger 4 impacted the far side of the

(229.3 degrees E, 15.5 degrees S) at at 12:49:53 UT on April 26, after 64 hours of flight.

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedin ...

officials tried to put a positive spin on the mission, noting that it was the first time an

American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, pe ...

spacecraft had reached the surface of the Moon and that the probe was "far more sophisticated" than the

Soviet The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, ...

Luna 2 ''Luna 2'' ( rus, Луна 2}), originally named the Second Soviet Cosmic Rocket and nicknamed Lunik 2 in contemporaneous media, was the sixth of the Soviet Union's Luna programme spacecraft launched to the Moon, E-1 No.7. It was the first spa ...

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

, was the first American spacecraft to reach another celestial body. Although the spacecraft did not achieve its primary objective, the Atlas-Agena-Ranger combination performed without fault for the first time. It acquired the dubious honor of being the first spacecraft to impact the far side of the Moon as well.

References

External links

Lunar impact: A history of Project Ranger (PDF) 1977Reuters.com
Planned lunar missions
Reuters.com
Chronology - Five key dates in the race to the Moon {{Use American English, date=January 2014 4 Spacecraft launched in 1962 Spacecraft that impacted the Moon 1962 on the Moon

Spacecraft design

Mission

References

See also

External links