Abbreviations and acronyms:
Corrected Transcript and Commentary Copyright © 2003 by W. David Woods and Ronald Hansen. All rights reserved.
Last updated 2017-02-17
Acquisition Of Signal
The spacecraft has reacquired radio contract with Mission Control. In Earth orbit this happens
when the spacecraft appears above the horizon of a communications station. At the Moon,
this happens when the spacecraft reappears from behind the Moon. During the coast phase
to and from the Moon, the spacecraft is in almost continuous contact with one of the main
Ascent Propulsion System (LM) or Auxiliary Propulsion System (S-IVB)
It's either the main engine system of the ascent (upper) stage of the LM, or
the attitude control system of the third stage of the Saturn V.
Apollo Range Instrumentation Aircraft
These aircraft were used as relays for communications and telemetry between the spacecraft
and Houston. Although not as capable as fixed ground stations or ships, they could be quickly
deployed to anywhere they were needed.
Blunt End Forward
The spacecraft was flying backwards as opposed to SEF (sharp end forward).
Body-Mounted Attitude Gyro
A set of rate gyros use to measure how fast the spacecraft is turning around its pitch,
roll, and yaw axes.
Boost Protective Cover
See launch escape system.
The leader of the spacecraft crew.
Center of Gravity
A theoretical point at which all the mass of an object is concentrated.
The part of the Apollo spacecraft where the astronauts live and work during their flight
to the Moon and back. Its also the only part that can reenter the Earth's atmosphere.
Command Module Computer
The command modules control and navigation computer.
Command Module Pilot
The crew member responsible for flying and running the command module (CM).
Command Module Simulator
A computer controller replica of the CM used for training and trying out new
Crew Optical Alignment Sight
A window mounted sight used by the command module pilot to line up with the lunar module
Contingency Orbit Insertion
If the S-II stage has burned long enough, orbit can still be reached even if the S-II stage
doesn't finish its burn. If the S-IVB has burned long enough, even if it doesn't finish its
burn, orbit can be reached using the SPS engine.
Command and Service Modules
For most of a flight, the command and the service modules work together as one spacecraft.
Just before the landing, the command module separates from the service module and brings
the astronauts back to Earth.
Digital to Analog Converter
Converts digital signals into analog signals.
The difference in pressure, usually in pounds per square inch (PSI) between the CM and the LM.
The difference between two velocities, usually due to a burn.
Digital Event Timer
Descent Orbit Insertion
The DOI burn lowered the perilune
far enough to permit the
actual landing to be started when the spacecraft reached the perilune.
Descent Propulsion System
The LM propulsion system used during the lunar landing.
Data Storage Equipment
A system that recorded spacecraft data and the conversations of the astronauts.
Display and Keyboard
This was the computer's input/output device. Although the computer didn't have
a mouse, it did have two hand controllers, the RHC
and the TVC.
Electronic Control Assembly
Environment Control System
More than just air conditioning, it also provided the crew with oxygen and water while
eliminating carbon dioxide and waste water.
Emergency Detection System
An onboard system that monitored the launch and the launcher looking for serious problems
that would require the launch to be aborted.
Electrical, Environmental, and Communications controller
The man in MOCR (mission control) who looked after these subsystems during a flight.
Earth Far Horizon
The whole Earth is too big to be used as a navigation fix.
Entry Monitor Subsystem
Its primary job was to monitor the reentry phase of a mission, it was also used to
measure the delta V of a burn.
Electrical Power Subsystem
Provided the other spacecraft systems with electrical power.
Flight Director Attitude Indicator
An artificial horizon that allowed the astronauts to keep track of where the
spacecraft was pointing.
Flight Dynamics Officer
The man in the MOCR (mission control) who was responsible for the spacecraft's
Gyro Display Coupler
Ground Elapsed Time
Nominally the time since launch, used for timing all mission events.
Guidance and Navigation
Gimbal Position Indicator
Shows the astronauts where the SPS engine gimbals are positioned so they can verify
that the engine is pointing in the right direction before and during a burn.
Inertial Measurement Unit
The IMU measures the amount and direction of the change in velocity of the spacecraft
See instrument unit
Kennedy Space Center
Moving between the CM and the LM.
Lower Equipment Bay
The second work place inside the CM, located just past the feet of the couches.
This is where the telescope and sextant are located.
Launch Escape System
Sometimes called the launch escape tower (LET), it's attached to the
top of the CM during the first part of the launch. In case of a launch abort, it will
pull the CM away from the launch vehicle and position the CM for a safe landing.
See Launch Escape System for more details
Launch Escape Tower
Lunar module Guidance Computer
The lunar modules control and navigation computer.
The lunar lander
Lunar Module Pilot
The LM systems expert. The spacecraft commander actually flew the LM.
Lunar Module Simulator
A computer controlled replica of the LM used for training and trying out new
Lunar Orbit Insertion
The long burn performed behind the Moon to slow the spacecraft enough to enter
into lunar orbit.
Lunar Orbit Rendezvous
The process of bringing the CSM and LM back together after they have separated
in lunar orbit.
Loss Of Signal
The spacecraft is out of radio contact with the ground because it's either
below the horizon of all of the communications stations or it's behind the
Hycon Lunar Topography Camera
A movie camera used to document future landing sites and areas of scientific interest.
Launch Umbilical Tower
Launch Vehicle Digital Computer
Located in the instrument unit, it controlls the launch
Maximum dynamic pressure (q)
A very critical point during a launch when a rocket is experiencing the maximum
The Saturn V launcher
The term, however, is not specific to the Saturn V and can be used for any rocket.
Mission Control Center
Often just called Mission Control.
Manual Thrust Vector Control
The SPS engine of the CSM uses a set of gimbals to control the thrust direction during
a burn. Although this is usually done automatically, the astronauts can control
it manually with the rotational control.
On the Job Training
Also "learning by doing". Often a subtle way of saying that the training was insufficient.
Oxygen Purge System
An emergency oxygen system that the astronauts carry on top of their backpacks during
their Moon walks.
Orbital Rate Drive Electronics Apollo LM
When the spacecraft is in orbit around the Earth or the Moon, the ORDEAL can be used
to control the FDAI so that it will show where the horizon is.
Null (do nothing) program
This program is just an idle, do-nothing loop. However, it needs to be running
whenever the computer is being updated from the ground.
Realign the guidance platform program
A program that ran both on the CMC and the LGC to
realign each spacecrafts guidance platform.
Pulse Code Modulation
Digital data transmission.
Powered Descent Initiation
The actual lunar landing which used the LMs DPS to brake the LM out of orbit
and land it softly on the lunar surface.
Pulsed Integrating Pendulous Accelerometer
A very accurate instrument for measuring changes in the spacecraft velocity.
Passive Thermal Control
The slow rotation of the spacecraft to made sure that no part of it gets
either too hot or too cold.
Also called "barbecue mode".
Propellant Utilization Gauging
Part of the system that controls the mixture ratio of the SPS engine to ensure that
the fuel and oxidizer are being burned at the correct rates. This not only optimizes the
thrust of the engine, but also avoids having excessive amounts of fuel or oxidizer
left over in the tanks.
Propellant Utilization Gauging System
Reaction Control System
The CM, LM, and SM had groups of small thrusters that were used to control the attitude of
the spacecraft and in the case of the LM and SM, were also used to make small changes in
the flight path.
Reference to Stable Member Matrix
Rotation Hand Control
A joy stick used to manually control the attitude of the spacecraft.
Stabilization and Control System
The system that controlled the spacecraft attitude (where it was pointing).
Sharp End Forward
The CSM is flying with its nose pointing in the direction of flight.
Saturn V's first stage
See S-IC description for more details.
Saturn V's second stage
See S-II description for more details.
Saturn V's third stage
See S-IVB description for more details.
The large cylindrical back end of the spacecraft with the large SPS engine bell at its
Service Propulsion Subsystem
The main propulsion system of the CSM.
Time of Closest Approach
Time when the spacecraft comes closest to a ground target.
The SPS engine burn that took the spacecraft out of lunar orbit and send it back
towards the Earth.
Translation Hand Controller
This hand controller was used by the astronauts to move the spacecraft.
This was the second burn of the third stage (S-IVB) of the Saturn V which took the
spacecraft out of Earth orbit and sent it towards the Moon.
Spacecraft data that's automatically send to the ground.
Thrust Vector Control
This system aligns the thrust vector of the SPS engine with the center of gravity
of spacecraft. In simple terms, it keeps the SPS engine from turning the
spacecraft during burns.