Double-sided Apollo 15 sun compass mockup used in training for the mission, printed on June 18, 1971, 7 x 10.5, signed on the reverse in black felt tip, "Dave Scott, Apollo 15 CDR." The front features an 8″ diameter rotating disc which depicts "Mount Hadley," "Hadley Delta," "Bennett Hill," and "Hill 305," and has an affixed plastic "Mockup Bubble Level." The main card provides instructions for "Bearing Determination" and "Return to LM." The reverse provides "Nominal Shadow Data" and has a "Landing Point Update" area. In fine condition.
The sun compass proved to be of vital importance during the Apollo 15 mission. Due to a miscalculation by the JSC MCC during the lunar landing phase of the flight, the actual landing location of the lunar module was in doubt. Dave Scott used a sun compass like this one to take bearings on the landmarks shown on the compass dial during the Stand-Up EVA. He used it to determine the lunar module's exact location on the moon. The sun compass was to be used in the event of the lunar rover's failure. Use of the sun compass to determine a heading that lead to the fastest and straightest return back to the lunar module. As such, Dave Scott stored a sun compass similar to this lot under his seat during all three EVAs.
This particular sun compass, made of heavy cardstock, is a unique and inventive instrument designed to be lightweight and sturdy. The front portion of the compass includes the sun dial with landmarks of the Apollo 15 landing site as well as instructions on its use. The reverse includes a sun angle and time chart as well as a hand drawn range finding device that Dave Scott would have used to figure the distance to the lunar module. Scott has said that the sun compass was a very clever answer for finding one's way on the lunar surface.
Sun compasses date back into the ages and are used to determine direction by the use of the sun and time of day. Due to the failure of magnetic compasses in the high latitudes, the sun compass was used in the exploration of the Earth's poles. Polar explorer Adm. Richard Byrd used a sun compass designed by Albert Bumstead of the NGS to chart his way to the North Pole by air in the 1920s. Since the moon has a very weak magnetosphere, a normal compass would be of no use in determining direction. The sun compass included here solved the problem of manual navigation on the moon.
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