Refsmmat
Encyclopedia
REFSMMAT is a term used by guidance, navigation, and control system flight controller
s during the Apollo program
, which carried over into the Shuttle Program
. REFSMMAT stands for "Reference to Stable Member Matrix". It is a numerical definition of a fixed orientation in space and is usually (but not always) defined with respect to the stars. It was used by the Apollo PGNCS
as a reference to which the gimbal-mounted platform at its core should be oriented to. Every operation within the spacecraft that required knowledge of direction was carried out with respect to the orientation of the guidance platform, itself aligned according to a particular REFSMMAT. During an Apollo flight, the REFSMMAT being used, and therefore the orientation of the guidance platform, would change as operational needs required it, but never during a guidance process—that is, one REFSMMAT might be in use from launch through Trans-Lunar Injection, another from TLI to Midpoint, but would not change during the middle of a burn or set of maneuvers.
For example, it was considered good practice to have the spacecraft displays show some meaningful attitude value that would be easy to monitor during an important engine burn. Flight controllers at mission control in Houston would calculate what attitude the spacecraft had to be at for that burn and would devise a REFSMMAT that matched it in some way. Then, when it came time for the burn, if the spacecraft was in its correct attitude, the crew would see their 8-ball display a simple attitude that would be easy to interpret, allowing errors to be easily tracked and corrected.
In the hallowed halls of mission control, Captain Refsmmat was a Kilroy
-type character, first drawn by flight controller Ed Pavelka as the "ideal mission controller", as an aid to the esprit de corps within the mission control team.
Flight controller
Flight controllers are personnel who aid in the operations of a space flight, working in Mission Control Centers such as NASA's Mission Control Center, or ESA's Operations Center. Flight controllers sit at computer consoles and use telemetry to monitor in real time various technical aspects of a...
s during the Apollo program
Project Apollo
The Apollo program was the spaceflight effort carried out by the United States' National Aeronautics and Space Administration , that landed the first humans on Earth's Moon. Conceived during the Presidency of Dwight D. Eisenhower, Apollo began in earnest after President John F...
, which carried over into the Shuttle Program
Space Shuttle program
NASA's Space Shuttle program, officially called Space Transportation System , was the United States government's manned launch vehicle program from 1981 to 2011...
. REFSMMAT stands for "Reference to Stable Member Matrix". It is a numerical definition of a fixed orientation in space and is usually (but not always) defined with respect to the stars. It was used by the Apollo PGNCS
Apollo PGNCS
The Apollo Primary Guidance, Navigation and Control System was a self-contained inertial guidance system that allowed Apollo spacecraft to carry out their missions when communications with Earth were interrupted, either as expected, when the spacecraft were behind the moon, or in case of a...
as a reference to which the gimbal-mounted platform at its core should be oriented to. Every operation within the spacecraft that required knowledge of direction was carried out with respect to the orientation of the guidance platform, itself aligned according to a particular REFSMMAT. During an Apollo flight, the REFSMMAT being used, and therefore the orientation of the guidance platform, would change as operational needs required it, but never during a guidance process—that is, one REFSMMAT might be in use from launch through Trans-Lunar Injection, another from TLI to Midpoint, but would not change during the middle of a burn or set of maneuvers.
For example, it was considered good practice to have the spacecraft displays show some meaningful attitude value that would be easy to monitor during an important engine burn. Flight controllers at mission control in Houston would calculate what attitude the spacecraft had to be at for that burn and would devise a REFSMMAT that matched it in some way. Then, when it came time for the burn, if the spacecraft was in its correct attitude, the crew would see their 8-ball display a simple attitude that would be easy to interpret, allowing errors to be easily tracked and corrected.
In the hallowed halls of mission control, Captain Refsmmat was a Kilroy
Kilroy
- People :* Alix Kilroy , one of the first two women to have entered the administrative grade of the British Civil Service by examination* Bucko Kilroy , American football player and executive with the New England Patriots...
-type character, first drawn by flight controller Ed Pavelka as the "ideal mission controller", as an aid to the esprit de corps within the mission control team.