Every Apollo astronaut knew the code phrases Navi, Dnoces, and Regor,
which refer to the stars Gamma Cassiopeiae, Iota Ursa Majoris, and Gamma
Velorum, respectively. This trio of stars was (and likely is) used for visual
reference during spaceflight, and was a core component of Apollo mission
training for inertial navigation procedures.
These interesting code names, however, originated from a practical joke started by the Apollo 1 crew:
Gus Grissom’s middle name, Ivan, spelled backwards. Dnoces is
the word second spelled backwards, in reference to astronaut
White’s full name, Edward H. White II. Regor is Roger
Chaffee’s first name spelled backwards.
White, Grissom, Chaffee -- Natural Pranksters Credit: NASA
What started out as a small prank turned into NASA policy as a tribute to the three brave men who sacrificed their lives for NASA, for the United States and for human space exploration on January 27, 1967.