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"

References:

• NASA SP-4009, The Apollo Spacecraft: A Chronology, Volume IV; Scientific and Technical Information Office, National Aeronautics and Space Administration; Washington, D.C. 1978.
• Lunar sourcebook: a user's guide to the moon, edited by Grant H. Heiken, David T. Vaniman, and Bevan M. French; Cambridge University Press 1991; ISBN 0-521-33444-6.
• Lunar Ephemeris program for Macintosh by Warren Anderson, freeware available from info-mac archives
• Starry Night astronomy program for Macintosh by Peter Hanson, et al., shareware available from Sienna Software. Starry Night is also available from the info-mac archive referenced above.
• Personal interview with John Carl c. 1982.
• Lost Moon: The Perilous Voyage of Apollo 13 by Jim Lovell and Jeffrey Kluger, Houghton Mifflin, 1994. (I used a note from news broadcasts reported in this book to estimate the intended landing time for Apollo 13. The original mission plan is not listed in any of the above references.)

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.