Chain: Event Data
Reports certain data at defined event times during each interval,
for strands consisting of only two objects. The 'From-object' is
the first object listed in the strand; the 'To-object' is the second
object listed. Values are reported for each strand access interval that
lies within the requested report intervals.
The azimuth and elevation angles are reported with respect to a frame determined
by the first object. The azimuth angle is the angle from the X axis
(positive about the Z-axis) to the projection of the apparent relative position
vector into the XY plane. The elevation is the angle of the apparent relative position
vector from the XY plane, with positive angles being used
when the vector has a negative Z component. When the first object is a Facility, Place, or Target,
the XYZ frame is Topocentric (X aligned with North, Y aligned with East, and Z aligned with the
detic nadir of the detic subpoint of the first object with respect to its central body).
When the first object is a Satellite, Missile, or LaunchVehicle, the XYZ frame is CbiVVLH
(inertial vehicle velocity local horizontal frame, with the Z axis aligned with the
anti-radial direction and the X axis constrained toward the inertial velocity direction).
When the first object is an Aircraft, GroundVehicle, or Ship, the XYZ frame is CbfVVLH
(fixed vehicle velocity local horizontal frame, with the Z axis aligned with the
anti-radial direction and the X axis constrained toward the central body fixed
velocity direction) when the central body fixed velocity is not close to zero; when
the velocity is close to zero, then the Topocentric frame is used. When the first object
is a Sensor, then the frame is determined by its parent object as described above.
Type: Interval data
Availability: Reports
Name | Description |
---|---|
AOS | The event time is the start time of the interval (a.k.a. acquisition of signal). |
LOS | The event time is the end time of the interval (a.k.a. loss of signal). |
TME | The event time is the time of maximum elevation during the interval. |
TCA | The event time is the time of closest approach (i.e., minimum range) during the interval. |