The non-rotating coordinate system
coincident with the Fixed system evaluated at the object's
coordinate reference epoch.
| Name |
Dimension |
Type |
Description |
| Time |
DateFormat |
Real Number |
Time. |
| x |
DistanceUnit |
Real Number |
The X component of the position vector. |
| y |
DistanceUnit |
Real Number |
The Y component of the position vector. |
| z |
DistanceUnit |
Real Number |
The Z component of the position vector. |
| vx |
Rate |
Real Number |
X Cartesian component of velocity. |
| vy |
Rate |
Real Number |
Y Cartesian component of velocity. |
| vz |
Rate |
Real Number |
Z Cartesian component of velocity. |
| Range |
DistanceUnit |
Real Number |
The range (i.e., distance between the primary and
secondary object) at the given time. |
| Range Rate |
Rate |
Real Number |
The rate of change of the magnitude of the relative
position vector. This is computed using the analytical formula
dot_product(relative_position_vector, relative_velocity_vector) /
magnitude(relative_position_vector). This is an exact formula when
the velocity is the derivative of position. Some propagators (e.g.,
SGP4, J2Perturbation, J4Perturbation), however, produce ephemerides
where the velocity is not exactly the derivative of position so
that this formula does not compute the derivative of range exactly
in such cases. |
| Speed |
Rate |
Real Number |
Magnitude of the velocity vector of the projection
of the selected point onto the reference plane. |
| Approach Angle |
AngleUnit |
Real Number |
The angle between the inertial velocity of the
primary object and the inertial velocity of the secondary object at
the given time |
| Miss Distance |
DistanceUnit |
Real Number |
The component of the relative position vector
perpendicular to the relative velocity vector. |
| Position Combined Cov Sigma |
Unitless |
Real Number |
Position difference measured in terms of the
combined position covariance of primary and target satellites.
Reports N where the current relative position vector lies on an N
sigma ellipsoid, where the ellipsoid is obtained from the sum of
the covariances matrices of the two objects. This can only be
computed if position covariance is available. |
| Position Cov
Sigma |
Unitless |
Real Number |
Position difference measured in terms of the
position covariance. Reports N where the current relative position
vector lies on a N sigma ellipsoid, where the ellipsoid if obtained
from the position covariance of the primary satellite. This can
only be computed if position covariance is available. |