the Wright brothers' 1903 Wright Flyers left propeller and a piece of fabric from its wing, along with a diamond-studded astronaut pin originally given to Slayton by the widows of the Apollo 1 crew. This pin had been intended to be flown on that mission and given to Slayton afterwards, but following the disastrous launch pad fire and subsequent funerals, the widows gave the pin to Slayton. Armstrong took it with him on Apollo 11. Site selection NASA's Apollo Site Selection Board announced five potential landing sites on February 8, 1968. These were the result of two years' worth of studies based on high-resolution photography of the lunar surface by the five uncrewed probes of the Lunar Orbiter program and information about surface conditions provided by the Surveyor program. The best Earth-bound telescopes could not resolve features with the resolution Project Apollo required. The landing site had to be close to the lunar equator to minimize the amount of propellant required, clear of obstacles to minimize maneuvering, and flat to simplify the task of the landing radar. Scientific value was not a consideration. Areas that appeared promising on photographs taken on Earth were often found to be totally unacceptable. The original requirement that the site be free of craters had to be relaxed, as no such site was found. Five sites were considered: Sites 1 and 2 were in the Sea of Tranquility (Mare Tranquillitatis); Site 3 was in the Central Bay (Sinus Medii); and Sites 4 and 5 were in the Ocean of Storms (Oceanus Procellarum). The final site selection was based on seven criteria: The site needed to be smooth, with relatively few craters; with approach paths free of large hills, tall cliffs or deep craters that might confuse the landing radar and cause it to issue incorrect readings; reachable with a minimum amount of propellant; allowing for delays in the launch countdown; providing the Apollo spacecraft with a free-return trajectory, one that would allow it to coast around the Moon and safely return to Earth without requiring any engine firings should a problem arise on the way to the Moon; with good visibility during the landing approach, meaning the Sun would be between 7 and 20 degrees behind the LM; and a general slope of less than two degrees in the landing area. The requirement for the Sun angle was particularly restrictive, limiting the launch date to