Close approach event data report. The report is divided into subsections with
each subsection listing close approach events of secondaries with the same
primary object.
The events are sorted in the order of the start time, SSC number of the secondary object, minimum range, and duration of each event.
When doing sorting, if the numbers are close (within 1 mm or within 1 millisec), then the next sort criterion is used (if one exists).
Interval data. Intended to be used only with elements from this same data provider.
| Name | Dimension | Type | Description |
|---|
| 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 |
| Collision Probability (Analytic) | Unitless | Real Number | The probability of collision computed using an analytic method based upon
Ken Chan's paper.
|
| Collision Probability (Maha) | Unitless | Real Number | The probability of collision computed based on the Mahalanabis distance method. |
| Collision Probability (Nonlinear - Bundles) | Unitless | Real Number | The probability of collision computed using a numeric method based upon modeling collision tubes as bundles of abutting parallelepipeds.
Nonlinear probability measures may return -1.0 if the user hits cancel during the computation, or for some values of the inputs, which indicates that the max sigma value should be made larger and the computation re-run. |
| Time In | DateFormat | Real Number | Start time of the event. |
| Collision Probability (Nonlinear - Cylinders) | Unitless | Real Number | The probability of collision computed using a numeric method based on a method of adjoining tubes (cylinders). The collision tube is broken into small sections, the probability associated with each section is computed, and then summed.
Nonlinear probability measures may return -1.0 if the user hits cancel during the computation, or for some values of the inputs, which indicates that the max sigma value should be made larger and the computation re-run. |
| Collision Probability (Numeric) | Unitless | Real Number | The probability of collision computed using a numeric method based upon
Sal Alfano's paper.
Collision Probability (Numeric) will return -1.0 as an error indicator when encounter plane's sigma X or sigma Z value is too small (less than 0.1 mm).
|
| Time Out | DateFormat | Real Number | Stop time of the event. |
| Time at Min Sep (TMS) | DateFormat | Real Number | The time of the minimum separation between the primary and secondary threat volumes. |
| Collision Probability (Patera 2005) | Unitless | Real Number | The probability of collision computed using an analytic method based upon Russell Patera's paper that appeared in the J. of Guidance, Control and Dynamics, vol. 28 (6), 2005. |
| Combined HardBodyRadius | SmallDistanceUnit | Real Number | The sum of the hard body radii of the primary and secondary objects. |
| ConjTCA Min Type | Unitless | Text | The type of the minimum conjunction range: either Local Minimum or EndPoint Minimum. |
| ConjTCA | DateFormat | Real Number | The time of closest approach (i.e., the minimum range) between the primary and
secondary objects that occurs during the conjunction (i.e., during the close
approach event interval). See also Time of Close Appr (TCA) which is computed
over a possibly larger time interval per event.
|
| Time of Close Appr (TCA) | DateFormat | Real Number | The time of closest approach (i.e., the minimum range) between the primary and
secondary bodies. The value is computed over the time interval produced by
the Range filter, which is likely larger than the time interval of the event itself.
See also ConjTCA.
|
| Duration | TimeUnit | Real Number | The duration of the event. |
| EncounterPlane Correlation XZ | Unitless | Real Number |
The XZ covariance correlation coefficient of the projection
of the relative position covariance into the encounter plane, as defined in
Ken Chan's paper. The Y axis is normal to the encounter plane, and is aligned
with the relative velocity vector at the time of close approach; the X axis
lies along the line between the primary and secondary at the time of close approach.
|
| EncounterPlane Normal Sigma | DistanceUnit | Real Number | The sigma value along the Y direction for the projection of the relative position covariance into the encounter plane, as defined in Ken Chan's paper. The Y axis is normal to the encounter plane, and is aligned with the relative velocity vector at the time of close approach; the X axis lies along the line between the primary and secondary at the time of close approach. |
| EncounterPlane Sigma AspectRatio | Unitless | Real Number | The Encounter Plane Sigma Max divided by the Encounter Plane Sigma Min. |
| EncounterPlane Sigma Max | DistanceUnit | Real Number | The length of the major axis of the ellipse defined by the projection
of the relative position covariance into the encounter plane, as defined in
Ken Chan's paper.
|
| Probability Linearity Speed (Coarse) | Rate | Real Number | The coarse estimate of the relative speed needed to insure that the linear probability computation is accurate. |
| Prim: Lat (TMS) | LatitudeUnit | Real Number | The primary object's detic latitude at the time of minimum separation. |
| Probability Linearity Speed (Fine) | Rate | Real Number | The refined estimate of the relative speed needed to insure that the linear probability computation is accurate. |
| Prim: Alt (TMS) | DistanceUnit | Real Number | The primary object's detic altitude at the time of minimum separation. |
| Short Term Encounter Duration | TimeUnit | Real Number | The duration of the encounter as computed using the short-term encounter assumption. Reference: V.T. Coppola (2012), Paper AAS 12-248. |
| TCA Uncertainty | TimeUnit | Real Number | The uncertainty in the time of closest approach computed from the relative position
uncertainty and the relative velocity at the time of the encounter.
|
| EncounterPlane Sigma Min | DistanceUnit | Real Number | The length of the minor axis of the ellipse defined by the projection
of the relative position covariance into the encounter plane, as defined in
Ken Chan's paper.
|
| Prim: Long (TMS) | LongitudeUnit | Real Number | The primary object's detic longitude at the time of minimum separation. |
| Short Term Encounter Start | DateFormat | Real Number | Start time of encounter according to short-term encounter assumption.
Reference: V.T. Coppola (2012), Paper AAS 12-248. |
| Short Term Encounter Start Since TCA | TimeUnit | Real Number | Duration from TCA of the encounter start according to short-term encounter assumption. Reference: V.T. Coppola (2012), Paper AAS 12-248. |
| EncounterPlane Sigma X | DistanceUnit | Real Number | The sigma value along the X direction for the projection
of the relative position covariance into the encounter plane, as defined in
Ken Chan's paper. The Y axis is normal to the encounter plane, and is aligned
with the relative velocity vector at the time of close approach; the X axis
lies along the line between the primary and secondary at the time of close approach.
|
| EncounterPlane Sigma Z | DistanceUnit | Real Number | The sigma value along the Z direction for the projection
of the relative position covariance into the encounter plane, as defined in
Ken Chan's paper. The Y axis is normal to the encounter plane, and is aligned
with the relative velocity vector at the time of close approach; the X axis
lies along the line between the primary and secondary at the time of close approach.
|
| Short Term Encounter Stop | DateFormat | Real Number | Stop time of encounter according to short-term encounter assumption. Reference: V.T. Coppola (2012), Paper AAS 12-248. |
| Short Term Encounter Stop Since TCA | TimeUnit | Real Number | Duration from TCA of the encounter stop according to short-term encounter assumption.
Reference: V.T. Coppola (2012), Paper AAS 12-248. |
| Short Term Assumption Duration | TimeUnit | Real Number | The duration that the short-term encounter assumption assumes is short. Reference: V.T. Coppola (2012), Paper AAS 12-248.
|
| EncounterPlane Theta | AngleUnit | Real Number | The orientation of the principal axis of the ellipse defined by the projection
of the relative position covariance into the encounter plane, as defined in
Ken Chan's paper.
|
| Prim: Radius (TMS) | DistanceUnit | Real Number | The magnitude of the position vector of the primary object at the time
of minimum separation.
|
| Max Collision Probability | Unitless | Real Number | The maximum probability of collision, as defined by Sal Alfano's paper. |
| Min Conj Range | DistanceUnit | Real Number | The range between the primary and secondary object at the ConjTCA. |
| Prim: Speed (TMS) | Rate | Real Number | The magnitude of the inertial velocity vector of the primary object at the time
of minimum separation.
|
| Min Range - CrossTrack | DistanceUnit | Real Number | The component of the minimum range vector from the primary object to the secondary object,
along the cross-track direction defined by the primary body's orbit (i.e., along
the orbit normal).
|
| Min Range - InTrack | DistanceUnit | Real Number | The component of the minimum range vector from the primary object to the secondary object, along the in-track direction defined by the primary body (the in-track direction completes a triad involving the radial and cross-track directions). |
| Prim: Lat (TCA) | LatitudeUnit | Real Number | The primary object's detic latitude at the time of close approach. |
| Min Range - Normal | DistanceUnit | Real Number | The component of the minimum range vector from the primary object to the secondary object,
along the normal direction defined by the primary body (the normal direction completes
a triad involving the tangential and cross-track directions, and is akin to the
radial direction).
|
| Prim: Long (TCA) | LongitudeUnit | Real Number | The primary object's detic longitude at the time of close approach. |
| Sigma Dilution Threshold | DistanceUnit | Real Number | The sigma value at which the probability of collision decreases with an increase
in covariance, as defined by Sal Alfano's paper.
|
| Prim: Alt (TCA) | DistanceUnit | Real Number | The primary object's detic altitude at the time of close approach. |
| Min Range - Radial | DistanceUnit | Real Number | The component of the minimum range vector from the primary object to the secondary object, along the radial direction defined by the primary body. |
| Prim: Radius (TCA) | DistanceUnit | Real Number | The magnitude of the position vector of the primary object at the time
of close approach.
|
| Sec: Lat (TMS) | LatitudeUnit | Real Number | The secondary object's detic latitude at the time of minimum separation. |
| Sec: Alt (TMS) | DistanceUnit | Real Number | The secondary object's detic altitude at the time of minimum separation. |
| Min Range - Tangential | DistanceUnit | Real Number | The component of the minimum range vector from the primary object to the secondary object,
along the tangential direction defined by the primary body (i.e., along
the inertial velocity direction of the primary).
|
| Sec: Long (TMS) | LongitudeUnit | Real Number | The secondary object's detic longitude at the time of minimum separation. |
| TCA Min Type | Unitless | Text | The type of the minimum range: either Local Minimum or EndPoint Minimum. |
| Prim: Speed (TCA) | Rate | Real Number | The magnitude of the inertial velocity vector of the primary object at the time
of close approach.
|
| TMS Min Type | Unitless | Text | The type of the minimum separation either Local Minimum or EndPoint Minimum. |
| Min Range | DistanceUnit | Real Number |
The range (i.e., distance between the primary and secondary object)
at the time of close approach. |
| Min Separation | DistanceUnit | Real Number or Text |
The separation distance between the primary and secondary threat volumes
at the time of minimum separation.
If the ellipsoids intersect, then the value will be "Intersect".
|
| Sec: Radius (TMS) | DistanceUnit | Real Number | The magnitude of the position vector of the secondary object at the time
of minimum separation.
|
| NumberID | Unitless | Text |
The number identifier of the secondary object involved in the close approach event.
If the object has no number identifier, then the value will be "Not Avail".
|
| Object Name | Unitless | Text | The names of the secondary object involved in the close approach event. |
| Sec: Speed (TMS) | Rate | Real Number | The magnitude of the inertial velocity vector of the secondary object at the time
of minimum separation.
|
| Primary Rev (TCA) | Unitless | Integer | The revolution (pass) number of the primary object at the time of close approach. |
| Range Sigma (TCA) | Unitless | Real Number | The value of the range between the objects measured at TCA, expressed in terms of sigma (i.e., the scale factor by which the combined covariance ellipsoid would need to be scaled to just touch the range vector). |
| Sec: Lat (TCA) | LatitudeUnit | Real Number | The secondary object's detic latitude at the time of close approach. |
| Range Uncertainty (TCA) | DistanceUnit | Real Number | The uncertainty in the range at the time of close approach.
The uncertainty is
computed by treating the ellipsoid size and orientation as a measure of the
position covariance for each object. The relative position covariance is then computed
and projected onto the line of sight direction between the two objects to compute the value.
|
| Sec: Long (TCA) | LongitudeUnit | Real Number | The secondary object's detic longitude at the time of close approach. |
| Sec: Alt (TCA) | DistanceUnit | Real Number | The secondary object's detic altitude at the time of close approach. |
| Relative Velocity | Rate | Real Number | The magnitude of the difference in the inertial velocities of the primary and
secondary objects
at the given time. |
| Sec: Radius (TCA) | DistanceUnit | Real Number | The magnitude of the position vector of the secondary object at the time
of close approach.
|
| Sec: Speed (TCA) | Rate | Real Number | The magnitude of the position vector of the secondary object at the time
of close approach.
|
| Secondary Rev (TCA) | Unitless | Integer | The revolution (pass) number of the secondary object at the time of close approach. |
| SourceID | Unitless | Text | The identifier of the object as used by the ephemeris source for the object. For example, the identifier for objects that use a GPS sem or yuma file is PRN-##. |
| SSC | Unitless | Text | SSC number of the satellite with out of date TLE data for the date selected. |
| StringID | Unitless | Text |
The string identifier of the secondary object involved in the close approach event.
If the object has no string identifier, then the value will be "Not Avail".
|
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