Critical LM subassembly used to gimbal landing radar during lunar descent
Lunar Module (LM) Landing Radar Antenna Pedestal Mount and Tilt Mechanism, an essential subassembly responsible for gimbling the LM Landing Radar as the spacecraft descended to the moon's surface. The mechanism with mount measures 13" x 12.25" x 10", with wire cluster, when extended, measuring approximately 20" in length. The base of the mechanism retains its original RCA parts label, which reads: "Antenna Pedestal Subassembly, Cont. No. NAS 9-1100, GAEC P.O. No. 2-18846-C, RCA P.O. No. 1DT-344-0005-L82 / Design Cont. No. RCA LESP-(B)-3621, Part No. RCA8345031-501, Unit 44, Serial No. 144, MFR 49671, U.S." Connecting ports terminating at either end of the wire cluster bear similar part numbers: "LSC-390-8-408621, 862, 6614-Deutsch, 22007-24-615-004" and "LSC-390-8-408611, 6542DD-Deutsch, 22007-24-61P-004." Upper shoulders stamped "A17" and "B17," with RCA stamp on crossbar reading "8661445-502."
The landing radar sensed the velocity and slant range of the LM relative to the lunar surface by means of a three-beam Doppler velocity sensor and radar altimeter. The radar antenna was interfaced to the LM via the pedestal/tilt mount assembly, which was bolted to the underside of the descent station and bears a tilt mechanism for tilting the antenna to either of two positions, and an electrical interface between the antenna assembly and the LM electronics package. On command, a tilt actuator motor moved the antenna to position #1 (Descent) or #2 (Hover). In the descent position the antenna group beam center was tilted 24 degrees with respect to the LM 'X' axis; in hover position, it was parallel to the LM X-Axis. During the lunar landing mission, the antenna was initially set to descent position for the descent phase. When the LM pitch-up maneuver occured (as the LM approached the ground), the pedestal/tilt mount repositioned the landing radar antenna to the hover position (and remained there until touch down on the lunar surface). A marvelous Apollo-era artifact that played an integral role in each of the program's six successful moon-landings.