Lunar Orbiter 4 was a robotic U.S. spacecraft, part of the Lunar Orbiter Program, designed to orbit the Moon, after the three previous orbiters had completed the required needs for Apollo mapping and site selection. It was given a more general objective, to "perform a broad systematic photographic survey of lunar surface features in order to increase the scientific knowledge of their nature, origin, and processes, and to serve as a basis for selecting sites for more detailed scientific study by subsequent orbital and landing missions". Accurate data was acquired from all other experiments throughout the mission. Radiation data showed increased dosages due to solar particle events producing low energy protons. The spacecraft was used for tracking until it struck the lunar surface due to the natural decay of the orbit no later than October 31, 1967, between 22 and 30 degrees W longitude.
{|class="wikitable"
|+Instruments
|-
| Lunar Photographic Studies:|| Evaluation of Apollo and Surveyor landing sites
|-
| Meteoroid<br />Detectors:|| Detection of micrometeoroids in the lunar environment
|-
| Caesium Iodide Dosimeters:|| Radiation environment en route to and near the Moon
|-
| Selenodesy:|| Gravitational field and physical properties of the Moon
|}
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Image:Atlas Agena launching Lunar Orbiter 4.jpg|Launch of Lunar Orbiter 4 from an Atlas-Agena rocket on May 4, 1967
Image:Lunar Orbiter 4 - FRAME 4079-H3 - DPLA - 659e5b52f0a881469578ef382cb20eda.jpg|Keldysh on May 16, 1967 ()
Image:Lunar Orbiter 4 - FRAME 4122-H1 - DPLA - ebcecfb905e2cc0301d8e53cac0d9d0b.jpg|Timocharis crater on May 19, 1967 ()
Image:Wichmann LO-IV-137H LTVT.JPG|Wichmann crater (lower right) and Wichman R (arc of ridges) on May 21, 1967
Image:Stadius crater (Lunar Orbiter 4).jpg|Image of Stadius crater
Image:Mare Orientale (Lunar Orbiter 4).png|Mare Orientale on the far side of the Moon, May 1967
Image:Lunar Orbiter 4151 h1 (cropped).jpg|Lunar Orbiter 4 image of Aristarchus crater (top) and Vallis Schröteri, May 1967
Image:Planitia Descensus NASA Lunar Orbiter iv 162 h1.jpg|Planitia Descensus, the landing site of Luna 9
</gallery>
See also
- Lunar Orbiter Image Recovery Project
- Exploration of the Moon
- List of artificial objects on the Moon
- List of missions to the Moon
- Lunar Orbiter 1
- Lunar Orbiter 2
- Lunar Orbiter 3
- Lunar Orbiter 5