posted 08-21-2023 10:53 PM               

Space Cover 715: Lunar Orbiter Program

The Lunar Orbiter program was a series of five lunar orbiter satellite missions launched by Atlas-Agena-D rockets from 1966 through 1967. The Lunar Orbiter satellites provided the first photographs from lunar orbit, photographed both the Moon and Earth, and helped select Apollo landing sites by mapping the Moon's surface.

All five missions were successful, and 99 percent of the lunar surface was mapped from photographs taken with a resolution of 200 feet or better. The missions were divided into two groups - low orbits related to Apollo program landing sites and high orbits for science objectives.

The Lunar Orbiter 1 to Lunar Orbiter 3 were dedicated to detailed imaging of 20 potential Apollo crewed lunar landing sites initially selected based on Earth-based telescopic observations. These were flown at low-inclination orbits.

Lunar Orbiter 4 and Lunar Orbiter 5 were devoted to broader scientific objectives and were flown in high-altitude polar orbits. Lunar Orbiter 4 photographed the entire nearside and nine percent of the far side, and Lunar Orbiter 5 completed the far side coverage and acquired medium (66 feet) and high (6 feet 7 inch) resolution images of 36 preselected areas.

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. The two cameras were placed so the area imaged in the high resolution area were centered within the medium resolution areas. The film needed to be moved during film exposure to compensate for the spacecraft velocity.

If asked about the first Earth-rise photo, people would likely say the classic photo taken aboard Apollo 8. However, the first pictures of Earth were taken by the Lunar Orbiter satellites. The very first Earth-rise over the Moon photograph was taken by Lunar Orbiter 1 in August, 1966. The first full picture of the whole Earth was taken by Lunar Orbiter 5 in August, 1967. A second photo of the whole Earth was taken by Lunar Orbiter 5 in November 1967.

A little known use of Lunar Orbiter program was the use of the Lunar Orbiter satellites for tracking purposes to evaluate the Manned Space Flight Network and Deep Space Network tracking stations and Apollo Orbit Determination Program, with three of the Lunar Orbiters - Lunar Orbiters 2, 3, and 5 - being tracked simultaneously from August through October 1967.

The Lunar Orbiters were all eventually commanded to crash on the Moon before their attitude control fuel ran out so they would not present navigational or communications hazards to later Apollo flights.

Covers were created for all of the Lunar Orbiter missions - pictured are covers for the launch of Lunar Orbiter 5. The launch of Lunar Orbiter 5 was at 6:33 p.m. Eastern Daylight Time at Cape Canaveral's Launch Complex 13. Interestingly the Space Craft Cover (with its insert shown) is postmarked August 1st while the Orbit Cover is postmarked August 2nd.

The United States also produced a Lunar Orbiter stamp - Scott 2571 "Moon & Lunar Orbiter" 29 Cent stamp in 1991.

posted 08-22-2023 05:31 PM               

Here's a really well-done commemoration of Lunar Orbiter 1 on Ecuador #1306 from 1966:

posted 08-24-2023 04:15 PM               

At the time these were big news events and provided spectacular photos and information about the mysterious moon. Because of these three successful programs and, of course, Apollo, our moon isn't as mysterious and unknown anymore.

The covers shown are excellent and well-done. Unfortunately, at the time I wasn't a space cover collector but did save newspapers and magazines pertaining to these pioneer lunar programs.