Page 77 - Apollo Moonships

The lunar spider 75
COMMUNICATIONS SYSTEM
VHF in–flight antenna
S–band steerable
The LEM’s crew was able to communicate using voice, antenna TV, and telemetry data signals, using the S-band and
VHF equipment of the Communications System (CS).
This unit provides both communications in flight and
on the lunar surface, establishing links between
the LEM and the Apollo mother ship (CSM), the LEM and the Manned Space Flight Network
(MSFN) on Earth, the LEM and any extravehicular astronaut (EVA), and also between the LEM’s crew and the Earth when both astronauts worked outside of the spaceship or drove the Lunar Roving Vehicle (see page 78) over the lunar terrain. All these contacts were possibly using a miscellaneous
of transceivers, amplifiers, and diplexers
in conjunction with six antennas mounted
around the ascent stage: two VHF in-flight
antennas, one VHF EVA antenna, two S-Band in-flight antennas, and one S-Band steerable antenna. As happened in the case of the CSM, when the LEM was flying on the far side of the moon, communications with Earth were impossible. When the LEM rested on the lunar surface, communications with the Command-Service Module were established using the MSFN as a relay.
VHF EVA antenna
VHF in–flight antenna
S–band in–flight antenna
+ X axis + Yaw
LUNAR LANDER AXIS
On Earth, the guidance involves only two coordinates: latitude and longitude. In space, a third dimension is introduced. The dimensional axes are X, Y and Z, and all spacecraft positions are related to them.
+ Y axis + Y Pitch
+ Z Roll + Z axis
– X axis
celestial navigation equipment, which included an alignment optical telescope (AOT) that operated as a sextant. The measurements collected by astronauts using the AOT were transferred to the guidance computer to calculate the position of the LEM in relation to certain fixed stars. During the landing and rendezvous maneuvers, the LEM navigated using the aid of two devices designed specifically for these phases of the flight: the landing radar and the rendezvous radar. Both devices inform the astronauts of the distance and velocity of the LEM relative to the target for landing, rendezvous, and docking.
To face contingencies, the lunar lander also had the Abort Guidance System (AGS), an independent device equipped with its own computer and inertial units that backed up the PGNCS. If the main guidance system failed, the astronauts could use the AGS to guide the ascent stage back to the CSM or move
it to a low lunar orbit, where they could be rescued by the Command Module pilot. During the Apollo missions, the AGS was never used to face an emergency on a real lunar landing mission, only on test flights.
Parabolic primary reflector
Hyperbolic secondary reflector
Trunnion
RENDEZVOUS RADAR
This device tracks the CSM in the lunar orbit and provides continued measurements for the PGNCS, which allowed the LEM’s crew to find the CSM in space and dock with it.
Shaft