A very rare and crucial piece of Apollo LM landing equipment. A Lunar Surface Sensor Probe measuring 72″ x approximately 1.5″ in diameter, serial number 0006. Probe consists of an aluminum tube with a switch at the end, and a spring-driven mechanism for rotating the probe to the extended position. The tube is covered with insulation made of gold-colored Kapton film, and black Inconel foil for the side facing the LM descent engine. A small access port near the end of the tube allowed access to the switch. An attached Grumman Removal tag indicates that the Lunar Surface Sensing Probe had been installed on a Lunar Module, “Vehicle No. 39.” This was LM-9, an early LM design originally intended for the Apollo 15 flight. LM-9 was replaced for Apollo 15 with LM-10, a more advanced design which could carry more equipment, including the Lunar Roving Vehicle. The reference designator block shows the reference designator “+Y,” indicating that this sensing probe had been installed on the right landing gear (when facing forward in the LM). Fine overall condition, with expected age wear, and some tears to foil and film.
Attached to three of the spacecraft's landing gear footpads were electromechanical devices know as the ‘Lunar Surface Sensing Probes.’ Using a spring loaded interlock assembly, these six foot long, electromechanical devices were deployed when the LM legs were unfolded, extending them below the footpads. During the final seconds of the lunar landing, these probes were the first objects to contact the Moon's surface. When any probe touches the surface, pressure on the unit's electric head switch will complete the circuit that activates the Contact light indicator on the LM's main control panel in front of the astronauts. "Contact Light" is announced by the astronauts, and the decent engine is throttled to a stop, allowing the LM to softly settle on the lunar surface. It is complete including much of its original gold Mylar and Kapton protective foil.
Research indicates that probes of 72″ were used on the LMs from Apollo 9 through Apollo 15, and that shorter, 60" probes were used on the LMs of Apollo 16 and Apollo 17. The change was due to the near crash of the LM on Apollo 15, when the engine was stopped too quickly after contact was made with the lunar surface and the LM dropped too far. This specific probe is a flight-ready, backup unit for the earlier Apollo flights. Flown probes, like the LM itself, are left on the lunar surface.
Terms and abbreviations used in our descriptions.