third shift. According to Kranz, flight directors during the program Apollo had a one-sentence job description, "The flight director may take any actions necessary for crew safety and mission success." Capsule communicators (CAPCOMs) were Fullerton, Parker, Young, Duke, Mattingly, Roosa, Alan Shepard and Joseph P. Allen. Mission insignia and call signs The insignia's most prominent feature is an image of the Greek sun god Apollo backdropped by a rendering of an American eagle, the red bars on the eagle mirroring those on the U.S. flag. Three white stars above the red bars represent the three crewmembers of the mission. The background includes the Moon, the planet Saturn, and a galaxy or nebula. The wing of the eagle partially overlays the Moon, suggesting humanity's established presence there. The insignia includes, along with the colors of the U.S. flag (red, white, and blue), the color gold, representative of a "golden age" of spaceflight that was to begin with Apollo 17. The image of Apollo in the mission insignia is a rendering of the Apollo Belvedere sculpture in the Vatican Museums. It looks forward into the future, towards the celestial objects shown in the insignia beyond the Moon. These represent humanity's goals, and the image symbolizes human intelligence, wisdom and ambition. The insignia was designed by artist Robert McCall, based on ideas from the crew. In deciding the call signs for the command module (CM) and lunar module (LM), the crew wished to pay tribute to the American public for their support of the Apollo program, and to the mission, and wanted names with a tradition within American history. The CM was given the call sign "America". According to Cernan, this evoked the 19th century sailing ships which were given that name, and was a thank-you to the people of the United States. The crew selected the name "Challenger" for the LM in lieu of an alternative, "Heritage". Cernan stated that the selected name "just seemed to describe more of what the future for America really held, and that was a challenge". After Schmitt stepped onto the Moon from Challenger, he stated, "I think the next generation ought to accept this as a challenge. Let's see them leave footprints like these." Planning and training Scheduling and landing site selection Prior to the cancellation of Apollo 18 through 20, Apollo 17 was slated to launch in September 1971 as part of NASA's tentative launch