Apollo Navigation Stars

20 July 2017

I can’t ever glance up at Menkent (Theta Centauri) without thinking what Michael Collins said when using the sextant onboard Apollo 11 and looking at the star, “Menkent. Menkent. God, what a star.”

Here is the NASA transcript:

Collins: “Okay, again, looking through the telescope. Okay, proceed to Menkent. There she goes. Menkent. Menkent. God, what a star.”

Buzz Aldrin cuts in: “Nobody in their right —”

Collins, speaking at the same time: “Menkent’s good.”

Aldrin again: “Nobody in their right mind would pick that one.” A moment later, “Hey, I sure wish you’d get out that — that star chart.”

Armstrong says: “Can’t see a thing, huh?”

Collins can see, but not too well. They plot Menkent, Nunki (Sigma Sagittarii) – at least Collins is pretty sure it’s Nunki (!) – and Atria (Alpha Trianguli Australis) for good measure.

Collins ends by saying: “God, I’ll tell you, the visibility through that telescope is a big disappointment.”

Astronomy is the oldest of the sciences, and quite possibly the oldest use of astronomy is navigating by the stars. The ancient Minoans, who lived on the Mediterranean island of Crete from 3000 to 1100 BC left records of using the stars to navigate and they surely weren’t the first to employ celestial navigation. How appropriate that the astronauts and engineers of the Apollo programme used celestial navigation to chart their way to the moon and back.  

The Apollo Guidance Computer (of which two were flown on each mission, one in the Command Module and one in the LEM) each had a list of 37 stars and various other bodies coded into the computer’s rope memory. The reference points were evenly distributed across the sky so as to maximise their utility during missions.

The three Apollo navigation stars, Navi, Dnoces, and Regor, were named in the spring of 1967 during an astronomy training session among the original Apollo 1 backup crew and Dr. Clarence Cleminshaw, Director of the Griffith Planetarium. This was in admiration, respect, and memory of three wonderful teammates who contributed all they had to the human exploration of the Moon.  The new names were simply parts of an Apollo 1 astronaut’s name spelled backwards: Gamma Cassiopeia became Navi for Virgil ‘Ivan’ Grissom; Suhail (Gamma Velorum) became Regor for ‘Roger’ Chaffee; and Talitha (Iota Ursa Majoris) became Dnoces for Ed White II (‘Second’)