Environmental Engineering Reference
In-Depth Information
D
Glossary
Angular momentum dump
See momentum dump.
Attitude
The orientation of the spacecraft in inertial space. Usually, atti-
tude defines the orientation of all three spacecraft axes with respect to an
inertial reference frame, though for spin-stabilized spacecraft, it often is
the case that only the orientation of the spin axis is specified.
Attitude actuator
A control hardware component that generates control
torques required to maintain spacecraft stability, null attitude errors, re-
orient the spacecraft to a new orientation with respect to an inertial ref-
erence frame, etc.
Attitude control
The mechanism for establishing and maintaining a desired
spacecraft orientation with respect to an inertial reference frame.
Attitude control accuracy
A quantitative measurement of the error in
maintaining the spacecraft attitude at its desired orientation with respect
to an inertial reference frame.
Attitude control torque
Torques intentionally applied to the spacecraft
to maintain or establish a desired spacecraft orientation with respect to
an inertial reference frame.
Attitude determination
The computation of the spacecraft orientation
relative to a specified reference frame. For celestial-pointing spacecraft,
the reference frame is usually either the geocentric inertial (GCI) frame
or the heliocentric inertial frame.
Attitude determination accuracy
A quantitative measurement of the
error in the computed spacecraft attitude.
Attitude dynamics
The study of a spacecraft's motion about its center of
mass.
Attitude maneuver
A commanded change in the spacecraft's desired at-
titude, as opposed to a torque applied to null errors in the actual attitude
relative to the desired attitude. A large attitude maneuver is called a
slew
.
Attitude matrix
A specification of the spacecraft orientation in direction
cosine matrix format. The direction cosine matrix is a 3
3 square matrix.
The nine elements of the matrix are the cosines of the angles between the
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