Author Topic: Apollo Landing Radar  (Read 311 times)

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Apollo Landing Radar
« on: 12/07/2017 03:55 AM »
The How and Why ~ 1968 Ryan Aeronautical; Moon Landing Guidance Radar

Jeff Quitney
Published on Dec 6, 2017

"Being manufactured here is the landing radar system for the Apollo Lunar Module, a spacecraft that will place America's astronauts on the Moon..."


The landing radar, which is located in the LM descent stage, is packaged in two replaceable assemblies. The antenna assembly forms directs, transmits, and receives four narrow microwave beams. To perform these functions, the antenna assembly is composed of two interlaced phase arrays for transmission and four space-duplexed planar arrays for recep­tion. The transmitting arrays form a platform; four quadrature-pair balanced microwave mixers, four dual audio­ frequency preamplifiers, two solid-state microwave transmitters, a frequency mod­ulation ( FM) modulator, and an antenna pedestal tilt mechanism are mounted on the platform. The electronics assembly contains the circuitry that is required to track, process, convert, and scale the Doppler and FM/continuous wave ( cw) re­ turns, which provide the velocity and slant range information to the LGC and to the display panels.

The transmitting antenna radiates the cw microwave energy from the solid-state velocity-sensor transmitter to the moon. Three separate receiving antennas accept the reflected energy. The received Doppler-shifted energy, which is split into quad­rature pairs, is mixed with a portion of the transmitted energy by microwave diodes that function as balanced mixers. The output of the crystal balanced mixers gives the frequency difference between the received signals and the transmitted signals. This frequency difference is the Doppler shift, which is directly proportional to the LM ve­locity with respect to the lunar surface along the detected microwave beam. The output of the altimeter transmitter ( a sawtooth waveform) is frequency mod­ulated at 130 hertz and is transmitted by a second antenna. The reflected energy received by the receiving antenna is split to form a quadrature pair and, with a sample of the transmitted signal, is coupled to balanced microwave mixers. The frequency difference at the output of the balanced mixers is proportional to the time difference between the transmission and the reception of the modulated energy, plus a Doppler­ shift factor. The undesired Doppler-shift factor is compensated for in the range computer.

The Apollo Lunar Module (LM), originally designated the Lunar Excursion Module (LEM), was the lander portion of the Apollo spacecraft built for the US Apollo program by Grumman Aircraft to carry a crew of two from lunar orbit to the surface and back. Designed for lunar orbit rendezvous, it consisted of an ascent stage and descent stage and was ferried to lunar orbit by its companion Command/Service Module (CSM), a separate spacecraft of approximately twice its mass, which also took the astronauts home to Earth. After completing its mission, the LM was discarded. It was capable of operation only in outer space; structurally and aerodynamically it was incapable of flight through the Earth's atmosphere. The Lunar Module was the first manned spacecraft to operate exclusively in the airless vacuum of space. It was the first, and to date only, crewed vehicle to land on a natural object in the solar system other than the Earth.

Originally a public domain film, slightly cropped to remove uneven edges, with the aspect ratio corrected, and one-pass brightness-contrast-color correction & mild video noise reduction applied.
The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and/or equalization (the resulting sound, though not perfect, is far less noisy than the original).

Tony De La Rosa