The relative geometry at the access
start time, expressed with respect to the local horizontal axes of
the source object.
| Name |
Dimension |
Type |
Description |
| Time |
DateFormat |
Real Number |
Time. |
| Azimuth |
LongitudeUnit |
Real Number |
Dihedral angle between north vector and velocity
vector about the detic nadir vector. The velocity vector is the
velocity of the object, as observed in the object's central body
fixed coordinate system. |
| Elevation |
AngleUnit |
Real Number |
Angle between the velocity vector and the local
horizontal plane. The velocity vector is the velocity of the
object, as observed in the object's central body fixed coordinate
system. |
| 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. |
| Azimuth Rate |
AngleRateUnit |
Real Number |
The rate of change of the azimuth angle. |
| Elevation Rate |
AngleRateUnit |
Real Number |
The rate of change of the elevation angle. |
| Relative
Velocity |
Rate |
Real Number |
The magnitude of the difference in the inertial
velocities of the primary and secondary objects at the given
time. |
| Horizontal Relative
Velocity |
Rate |
Real Number |
The projection of the relative velocity into the
horizontal (i.e., XY) plane. |