Posts: 273
From:
Registered: Jul 2016

posted 11-04-2018 07:35 PM               

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When was the list of primary landing sites for Apollo 11 through 20 first approved? Also, is there a list of primary and back-up landing sites for each Apollo mission?

If I am not mistaken, there was typically one primary site and two back-up sites for each mission and what determined a landing site choice was based on the day a mission launched within its three day launch window. In other words, if a mission failed to launch on the first day then the mission might have to go to the first back-up site instead, provided that the mission launched on the second day of the launch window. Is this correct?

If an Apollo mission launched from Earth on time to land at a primary site, was there any situation in lunar orbit that might have had the mission landing at one of its back-up sites instead?

Posts: 891
From: Vancouver, WA, USA
Registered: Feb 2012

posted 11-05-2018 05:54 PM               

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Apollo 11 had three target sites, ALS 2 (Mare Tranquillitatis), ALS 3 (Sinus Medii), and ALS 5 (Oceanus Procellarum). After 11 successfully landed at ALS 2, Apollo 12 was targeted for either ALS 7 (Surveyor III) or, if launch were delayed slightly, for 6R (Surveyor I).

Once 12 made its pinpoint landing at ALS 7, each later Apollo mission was targeted for only one specific area (e.g. 13 and later 14 were targeted for the Fra Mauro Formation) but there were two or three landing sites within that area. The two "backup sites" for Fra Mauro were about a mile to two miles west of the primary site. I do not know if similar "backup sites to the west of the primary site" existed for Apollos 15, 16, and 17 as Apollo was consistently demonstrating that it could land where it was supposed to.

Posts: 273
From:
Registered: Jul 2016

Posts: 891
From: Vancouver, WA, USA
Registered: Feb 2012

posted 11-06-2018 09:02 AM               

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ALS, Apollo Landing Site, numbers were assigned to prime candidates for the first lunar landing. By the beginning of 1969, they had been whittled down to five, then down to three. In preparation for Apollo 12, the original sites in Oceanus Procellarum were eliminated and entirely new ones were added, some had ALS designations and others did not. There were many landing site designation systems.

When you read "To A Rocky Moon" you will understand a bit better the give and take between Flight Operations and the lunar scientists. Landing sites for the first three missions were dictated by the operations people (who constantly kept revising their predictions of the C/SM and the LM flight capabilities). This is a very complicated subject with no easy answer.

Another great book on the subject, albeit very expensive, is "The International Atlas of Lunar Exploration" by Philip Stooke. The number of potential Apollo landing sites that were considered at one time or another is staggering.