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Apollo Landing Time

How Apollo Handled the Lighting Issue

This page is part of the discussion of the best time to land the Artemis Project spacecraft on the Moon. So if you haven't visited that page yet, you might want read it first to understand how the information from the Apollo flights fits into the story.

Back in the Sixties, NASA asked a young engineer named John Carl to figure out when would be the best time to land. John developed the criteria and analyzed the surface of the Moon to determine where the sun should be when the spacecraft touches down on the Moon. The analysis is the same for landings in the first decade of the 21st century as it was back then, so we'll follow the same rules for the Artemis Project landings.

Here's a closer look at the details for when and where the Apollo spacecraft landed, and where the Sun was. The illustrations in the table below might be a bit off, east-to-west, because the program I used to generate the pictures of the Moon doesn't adjust for its libration angle. I'll fix that when I can.

Apollo Moon Landings

Item Apollo 11 Apollo 12 Apollo 13 Apollo 14 Apollo 15 Apollo 16 Apollo 17
Moon Phase
Date 20 Jul 69 3:18 PM 19 Nov 69 12:55 PM 15 Apr 70 6:30 PM 5 Feb 71 3:17 PM 30 Jul 71 5:16 PM 20 Apr 72 8:23 PM 11 Dec 72 1:55 PM
Site Mare Tranquillitatis Oceanus Procellarum Fra Mauro Fra Mauro Hadley-Appenine Descartes Taurus-Littrow
Latitude 0.7 N 3.2 S 3.7 S 3.7 S 26.1 N 9.0 S 20.2 N
Longitude 24.3 E 23.4 W 17.5 W 17.5 W 3.7 N 15.5 E 30.8 E
Phase 6.29 9.86 9.86 9.42 8.58 7.20 5.93
Age 70.62 129.65 115.52 123.96 95.70 96.25 66.33
R.A. 12 h 29m 0h 22m 9h 36m 5h 14m 14h 34m 8h 38m 21h 48m
Dec -4.57 4.29 15.97 27.68 -20.58 17.87 -9.86
Julian 2440423.39 2440545.29 2440692.52 2440987.89 2441163.47 2441428.56 2441163.29
(.)Alt 10 36' 14" 10 12' 10" 5 25' 47" 15 34' 26" 5 25' 47" 24 04' 53" 12 20' 23"
(.)Az 88 08' 06" 91 16' 14" 90 25' 59" 91 01' 05" 90 25' 59" 86 08' 53" 96 05' 38"


In the table above, the date, time, and observing site information are based on an observer in Houston, Texas, at 29.5N latitude, 90W longitude. Latitude and Longitude are the location of the landing site on the Moon. Phase is the phase angle of the Moon, measured in days. Age is the Moon's age angle in degrees. Right Ascension and Declination tell where the Moon is located in the sky. The Julian Date is the time scale most used by astronomers, measured in days since the founding of Rome. Altitude and Azimuth are the position of the Sun in the lunar sky with respect to the lunar landing site.

The altitude of the Sun above the local lunar horizon at landing is the most revealing number for the Apollo flights. The Sun angle for these flights varied between about 5 degrees and 24 degrees, with the Sun between 12 and 15 degrees above the horizon for most of the flights.

Earth Orbit to Lunar Surface

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