Lunar Orbiter

Lunar Orbiter Program

The Lunar Orbiter program was a series of five robotic spacecraft launched by the United States 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 far side, and Lunar Orbiter 5 completed the far side coverage and acquired medium (20 m) and high (2 m) resolution images of 36 pre-selected areas.

Spacecraft Subsystems
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The components of the spacecraft are shown in the above illustration. Four solar panels provided power for the spacecraft and recharging its batteries. While in the shadow of the moon, power was supplied by the batteries. Thrust to change the orbit of the spacecraft came from the rocket engine. Four small thrusters were used to turn the spacecraft to point in the desired direction. This was essential to keep the cameras pointed at the area to be imaged or orient the craft properly before firing the rocket engine. The Inertial Reference Unit (IRU) keeps track of changes in spacecraft orientation. The Sun sensor and star tracker allow the onboard computer to determine the precise orientation of the spacecraft. Two radio antennas allowed communication with the control station on Earth. The omni directional antenna allows low data rate communications for receiving commands, and transmitting status of onboard systems regardless of the spacecraft orientation. The directional antenna is used to transmit the large image files to Earth. The main payload is the camera system. It consists of two cameras: one with a wide-angle lens (80 mm) and the other with a telephoto lens (610 mm).

Mission Descriptions

Lunar Orbiter 1

Launched August 10 1966

Imaged Moon: August 18 to 29 1966

Apollo landing site survey mission

Lunar Orbiter 2

Launched November 6 1966

Imaged Moon: November 18 to 25 1966

Apollo landing site survey mission

Lunar Orbiter 3

Launched February 5 1967

Imaged Moon: February 15 to 23 1967

Apollo landing site survey mission

Lunar Orbiter 4

Launched May 4 1967

Imaged Moon: May 11 to 26 1967

Lunar mapping mission

Lunar Orbiter 5

Launched August 1 1967

Imaged Moon: August 6 to 18 1967

Lunar mapping and hi-res survey mission

Links

• List of Robotic Missions to the moon

External Links

• Wikipedia article on the Lunar Orbiter program