The spacecraft was placed in a
cislunar trajectory and injected into an elliptical near polar high lunar
orbit for data acquisition. The orbit was with an inclination of 85.5 degrees and a period of 12 hours. After initial photography on May 11, 1967 problems started occurring with the camera's thermal door, which was not responding well to commands to open and close. Fear that the door could become stuck in the closed position covering the camera lenses led to a decision to leave the door open. This required extra
attitude control maneuvers on each orbit to prevent light leakage into the camera which would ruin the film. On May 13 it was discovered that light leakage was damaging some of the film, and the door was tested and partially closed. Some
fogging of the lens was then suspected due to
condensation resulting from the lower temperatures. Changes in the attitude raised the temperature of the camera and generally eliminated the fogging. Continuing problems with the readout drive mechanism starting and stopping beginning on May 20 resulted in a decision to terminate the photographic portion of the mission on May 26. Despite problems with the readout drive the entire film was read and transmitted. The spacecraft acquired photographic data from May 11 to 26, 1967, and readout occurred through June 1, 1967. The orbit was then lowered to gather orbital data for the upcoming
Lunar Orbiter 5 mission. A total of 419 high-resolution and 127 medium-resolution frames were acquired, which covered 99% of the Moon's near side at resolutions from . 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. 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 ==See also==