NASA's Lunar Orbiter: Mapping out the Moon for Landing
John Williams shows a real Lunar Orbiter at the Virginia Air & Space Center and explains why it was critical in photographing the Moon's surface to find the best place to land men on the Moon for the Apollo Program.
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Space Intelligence shares fun facts and excitement about space history, current space missions and future space exploration. John Williams is an avid fan and young space historian. His videos are designed to educate others to learn more about space history and technology.
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Link: NASA
Five Lunar Orbiter missions were launched in 1966 through 1967 with the purpose of mapping the lunar surface before the Apollo landings. All five missions were successful, and 99% of the Moon was photographed with a resolution of 60 m or better. The first three missions were dedicated to imaging 20 potential lunar landing sites, selected based on Earth-based observations. These were flown at low inclination orbits. The fourth and fifth missions were devoted to broader scientific objectives and were flown in high altitude polar orbits. Lunar Orbiter 4 photographed the entire nearside and 95% of the farside, and Lunar Orbiter 5 completed the farside coverage and acquired medium (20 m) and high (2 m) resolution images of 36 pre-selected areas. The images at the top of the page show the Lunar Orbiter spacecraft with the high and medium resolution cameras at the center, and an image of the crater Tycho taken with the Lunar Orbiter 5 medium resolution camera.
The Lunar Orbiters had an ingenious imaging system, which consisted of a dual-lens camera, a film processing unit, a readout scanner, and a film handling apparatus. Both lenses, a 610-mm narrow angle high-resolution (HR) lens and an 80-mm wide-angle medium resolution (MR) lens, placed their frame exposures on a single roll of 70 mm film. The axes of the two cameras were coincident so the area imaged in the HR frames were centered within the MR frame areas. The film was moved during exposure to compensate for the spacecraft velocity, which was estimated by an electric-optical sensor. The film was then processed, scanned, and the images transmitted back to Earth.
NASA Solar System:
In Depth: Lunar Orbiter 1
The Lunar Orbiter program originated in response to the need to obtain detailed photographs of potential Apollo landing sites. NASA planned to launch a series of three-axis stabilized spacecraft, each with four solar panels and a main engine (derived from an Apollo attitude control thruster) for lunar orbit insertion.
The primary instrument on the spacecraft was a 150-pound (68-kilogram) Eastman Kodak imaging system (using wide and narrow-angle lenses) that could develop exposed film, scan the images, and send them back to Earth.
In a twist that was not known until after the end of the Cold War, the Eastman Kodak camera flown on NASA's Lunar Orbiters was originally developed by the National Reconnaissance Office (NRO) and flown on the Samos E-1 spy satellite.
The narrow-angle pictures taken by this system provided resolution of 200 to 260 feet (60 to 80 meters), while the wide-angle photos showed resolutions up to 0.3 miles (0.5 kilometers).
Lunar Orbiter 1 was launched into a parking orbit around Earth before its Agena upper stage fired at 20:04 UT to insert it on a translunar trajectory. On the way to the Moon, the spacecraft’s Canopus star tracker failed to acquire its target, probably because the spacecraft’s structure was reflecting too much light. Flight controllers used a backup method by using the same sensor, but with the Moon to orient the vehicle.
The vehicle also displayed higher than expected temperatures but successfully entered a 1,160 × 118-mile (1,866.8 × 189.1-kilometer) orbit around the Moon on Aug. 14, 1966, thus becoming the first U.S. spacecraft to do so.
The spacecraft’s primary mission was to photograph nine potential Apollo landing sites, seven secondary areas, and the Surveyor 1 landing site. By Aug. 28, 1966, Lunar Orbiter 1 had completed its main photography mission, having exposed a total of 205 frames, of which 38 were taken in the initial orbit and 167 in lower orbits, covering an area of 2 million square miles (5.18 million square kilometers).
As planned, it photographed all nine potential Apollo landing sites as well as 11 sites on the far side of the Moon. Some of the high-resolution photos were blurred due to smearing (stemming from problems in the imaging system), but the medium resolution images were the best lunar surface images returned to date.
One of the images returned—unplanned but taken on Aug. 23, 1966—was the first picture of Earth taken from the vicinity of the Moon.