Description
The CovarianceUtilities Object allows a user to calculate a covariance based on a set of states, and calculate random states generated based on a covariance. See the Orbit Determination Guide for more information.
Users cannot create instances of this type of object. However, users can access instances of this object type that have been created indirectly, for example as children of other objects. Users can also access any static properties and methods on this object type.
Inheritance Hierarchy: Object>CovarianceUtilities
Available In Editions:
Engineer
Mission
Timing Precision Mode
This page describes functionality in millisecond timing precision mode.
Click here to see the documentation for this object in nanosecond timing precision mode.
Name

Description

Attributes

DeclaredName

The name of the object as declared.

Type: String
Access: ReadOnly

Name

The name displayed for this object in output windows such as views, plots, and reports.

Type: String
Access: Read/Write

ObjectId

The unique identifier for the object.

Type: Variable
Access: ReadOnly

ObjectType

The type of the object.

Type: String
Access: ReadOnly


Name

Description

ClearSavedStates

Clears previous saved states for this object.

GetFromFile

Load the object state from the specified FreeFlyer object file.

GetFromString

Load the object state from the specified string.

PutToFile

Convert the object state to FreeFlyer object xml and write to a file.

PutToString

Convert the object state to FreeFlyer object xml and return as a string.

ReferenceEquals

Returns 1 if the argument refers to the calling object and 0 otherwise.

Restore

Restore an object's state from a previously saved state.

Save

Save the object's state so that it can be restored later.


Name

Description

CalculateCovariance

Calculates and returns the covariance of a distribution of states.

CalculateMahalanobisDistance

Calculates the Mahalanobis distance of the state relative to the mean state given the specified covariance.

CalculateMeanAndCovariance

Calculates and returns the covariance of a distribution of states. Also, populates the meanState argument with the computed mean state.

CalculateUnscentedWeights

Computes the weighting factors for both mean and covariance sigma points based on the inputs of Alpha, Beta and Kappa for the Scaled Unscented Transformation.

GetCovarianceFromSigmaPoints

Computes the covariance matrix from the provided sigma points and weights matrices. The sigma points matrix must have the dimensions of N x 2N+1, where N is the number of states, and each column of the matrix is a sigma point state. The weights matrix is 2N + 1 x 2, where column 1 is the mean weights and column 2 is the covariance weights.

GetRandomState

Returns a random state from a zeromean Gaussian distribution described by the provided covariance matrix.

GetRandomStates

Returns multiple randoms state from a zeromean Gaussian distribution described by the provided covariance matrix. The resulting random states are returned in a column matrix.

GetSigmaPointsFromCovariance

Computes the values of the sigma points for all properties in the provided nominal state, using the arguments for the covariance, Alpha, Beta, and Kappa values.


