March 2008 Archives

Lunar Orbiter Imagery and Apollo Landing Site Selection

Source: Apollo Expeditions to the Moon Chapter 5.5 - Mapping and Site Selection

Meanwhile the third member of the automated lunar exploration team had already completed its work. The fifth and last Lunar Orbiter had been launched on August 1, 1967, nearly half a year earlier. When JPL and Hughes began to experience difficulties with Surveyor development, and with the Centaur in deep trouble, NASA decided to back up the entire proaram with a different team and different hardware. The Surveyor Orbiter concept was scrapped, and NASA's Langley Research Center was directed to plan and carry out a new Lunar Orbiter program, based on the less risky Atlas-Acena D launch vehicle. Langley prepared the necessary specifications and Boeing won the job. Boeing's proposed design was beautifully straightforward except for one feature, the camera. Instead of being all-electronic as were prior space cameras, the Eastman Kodak camera for the Lunar Orbiter made use of 70-mm film developed on board the spacecraft and then optically scanned and telemetered to Earth. Low-speed film had to be used so as not to be fogged by space radiation. This in turn required the formidable added complexity of image-motion compensation during the instant of exposure. Theoretically, objects as small as three feet could be seen from 30 nautical miles above the surface. If all worked well, this system could provide the quality required for Apollo, but it was tricky, and it barely made it to the launch pad in time to avoid rescheduling.

A photo of the crater on the Moon,Tycho

The youngest big crater on the Moon is Tycho, which is about 53 miles across and nearly 3 miles deep. These Orbiter V photographs reveal its intricate structure. (Area in the rectangle above is pictured in higher resolution below.) A high central peak arises from the rough floor, and the crater wall has extensively slumped. The comparative scarcity of small craters within Tycho indicate its relatively recent origin. Flow features seen in both pictures could have been molten lava, volcanic debris, or fluidized impact-ejected material. Surveyor VII landed about 18 miles north of Tycho, in the area indicated by the white circle above. Enlargements of these pictures show an abundance of fissures and large fractured blocks, particularly near the uppermost wall scarp.

Lunar Orbiter Missions - Table

Photographic Lunar Lunar Lunar Lunar Lunar
Parameters Orbiter 1 Orbiter 2 Orbiter 3 Orbiter 4 Orbiter 5
Launch Date 10-Aug-66 6-Nov-66 5-Feb-67 4-May-67 1-Aug-67
Periselene (km) 40.5 41 44 2668 97
Aposelene (km) 1857 1871 1847 6151 6092
Inclination (deg) 12 12 21 85.5 85
Period (h) 3.5 3.5 3.5 12 8.5,3.0
Impact date 29-Oct-66 11-Oct-67 10-Oct-67 31-Oct-67 31-Jan-68
Impact coordinates 7 N, 161 E 3 N, 119.1 E 14.32 N, 92.7 W ??, 22-30 W 2.79 S, 83 W
Acquisition dates 18-29 Aug 1966 18-25 Nov 1966 15-23 Feb 1967 11-26 May 1967 06-18 Aug 1967
Quantity of frames
High resolution 42 609 477 419 633
Medium resolution 187 208 149 127 211
Altitude range for photos (km) 44 - 1581 41 - 1519 44 - 1463 2668 - 6151 97 - 5758
Highest resolution
Periselene (m) 8 1 1 58 2
Aposelene (m) 275 33 32 134 125
Framelet width at periselene (m)
High resolution 200 170 185 11350 420
Medium resolution 1500 1300 1400 85100 3200

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