It was February of 1967, and the Space Race was on in earnest. The Soviets had beat the U.S. in launching the first satellite into orbit (1947), the first man into space (1961), the first woman into space (1963), and the first to soft-land an unmanned craft on the moon that transmitted photos of the lunar surface back to Earth (1966). The U.S. had all their hopes to catch up in a hurry entwined with NASA’s manned mission to the moon. The decade was moving on, and the next steps by NASA were critical to fulfilling President John Kennedy’s 1961 challenge of sending men to the moon and back before the end of the decade.
NASA was in the middle of sending five planned missions to photograph the entirety of the moon’s surface. The goal of the first three, the first of which was launched in 1966, was to scout for safe landing sites for the upcoming Apollo missions. In February of 1967, Lunar Orbiter 3 was launched. The final two explored scientific observational objectives, and flew polar orbits.
Since photos taken by the spacecraft were to be analyzed for potential landing sites, cameras equipped with sufficient resolution needed to be installed. Another engineering hurdle to overcome was a method to compensate for the speed of the spacecraft while taking the photos. Lunar Orbiter 3 was equipped with a medium resolution lens (80mm) and a high-resolution lens (610mm).
From February 15 to February 23, photo data was acquired according to a programmed automatic sequence and imaged onto 70 mm film. There was no viable digital photography technology in 1967. As a result, the spacecraft was outfitted with automatic film development. The processed film was then optically scanned and transmitted back to Earth as a video signal. On Earth, the signal was captured and fed into what was termed ground reconstruction equipment (GRE), which reassembled the signal data onto 35mm film positive subframes. Each photo required 26 individual subframes to produce a complete photograph, and 86 subframes for higher resolution images. The combined subframes produced a 20 x 24 inch format, from which contact negatives were made.
The spacecraft’s primary mission was deemed successful, despite the film advance mechanism’s spotty performance throughout the duration. However, the process functioned well enough until March 4, when the film advance motor burned out. Approximately 25% of the captured data was left unprocessed. All in all, the mission produced 149 medium resolution images and 477 high resolution images. The excellent quality of the images allowed for resolution down to one meter, an amazing feat considering they were taken from orbit. Combined with the photos from the first two Orbiters, 99% of the moon’s surface had been photographed. NASA chose eight preliminary landing sites, including the Sea of Tranquility site where Apollo 11 would land in 1969.
Lunar Orbiter 3 was also collecting data on the lunar gravitational field, radiation intensity and micrometeoroid impacts. For this task, the craft was positioned in a near equatorial orbit. The photographic data was to confirm the previous search data for possible site landings by Lunar Orbiter 1 and 2. The additional data from Lunar Orbiter 3 was vital to the planning of the manned Apollo missions set to begin two years from that point.
It continued to gather lunar data orbiting the moon. In August of 1967, NASA ground control sent the spacecraft into a circular orbit to simulate the trajectory of an Apollo spacecraft. It crashed into the lunar surface, as planned, on October 9, 1967. Each of the orbiters were designed to crash into the lunar surface so future missions would not have navigational or communication hazards to manage on their approach to the surface.
Mister Boomer, like most boomers, watched every single manned mission launch with great interest. However, interim unmanned missions were not given the same TV and press fanfare. These particular missions, though crucial for future moon landings, went under the radar for Mister B, until he researched them now.
How about you, boomers? Did you follow the preparatory unmanned missions by NASA in the 1960s?