Data Providers: AdvCAT: Events by Time In

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).

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 using the Maha 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".

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 using the Maha 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".