Data Providers: Satellite: Velocity Projected Covariance: ICRF

International Celestial Reference Frame. The ICRF is the best realization of an inertial frame constructed to date, and thus represents an improvement upon the theory behind the J2000 frame. While the ICRF and J2000 frames themselves are very close, they are not identical; moreover, the J2000 frame rotates (very slowly) over time with respect to the ICRF frame.

Name	Dimension	Type	Description
Time	DateFormat	Real Number	Time.
Sigma Xd	Rate	Real Number	Square root of the fourth diagonal component of the covariance matrix.
Sigma Yd	Rate	Real Number	Square root of the fifth diagonal component of the covariance matrix.
Sigma Zd	Rate	Real Number	Square root of the sixth diagonal component of the covariance matrix.
Correlation XdYd	Unitless	Real Number	XdYd correlation coefficient of the covariance matrix.
Correlation XdZd	Unitless	Real Number	XdZd correlation coefficient of the covariance matrix.
Correlation YdZd	Unitless	Real Number	YdZd correlation coefficient of the covariance matrix.
VelCovMtx XX	Rate Squared	Real Number	XX Component of the Velocity Covariance Matrix.
VelCovMtx YX	Rate Squared	Real Number	YX Component of the Velocity Covariance Matrix.
VelCovMtx YY	Rate Squared	Real Number	YY Component of the Velocity Covariance Matrix.
VelCovMtx ZX	Rate Squared	Real Number	ZX Component of the Velocity Covariance Matrix.
VelCovMtx ZY	Rate Squared	Real Number	ZY Component of the Velocity Covariance Matrix.
VelCovMtx ZZ	Rate Squared	Real Number	ZZ Component of the Velocity Covariance Matrix.
YPR321 yaw	AngleUnit	Real Number	Yaw angle between the two sets of axes. Defines rotation about the z-axis of the reference set, which occurs first when using 321 (or YPR) sequence in YPR angles representation.
YPR321 pitch	AngleUnit	Real Number	Pitch angle between the two sets of axes. Defines rotation about the y-axis of the reference set, which occurs second when using 321 (or YPR) sequence in YPR angles representation.
YPR321 roll	AngleUnit	Real Number	Roll angle between the two sets of axes. Defines rotation about the x-axis of the reference set, which occurs third when using 321 (or YPR) sequence in YPR angles representation.
Euler323 precession	AngleUnit	Real Number	Precession angle between the two sets of axes. Defines rotation about the z-axis of the reference set, which occurs first when using 323 sequence in Euler angles representation.
Euler323 nutation	AngleUnit	Real Number	Nutation angle between the two sets of axes. Defines rotation about the y-axis of the set rotated through precession, which occurs second when using 323 sequence in Euler angles representation.
Euler323 spin	AngleUnit	Real Number	Spin angle between the two sets of axes. Defines rotation about the z-axis of the set rotated through precession and nutation, which occurs third when using 323 sequence in Euler angles representation.
q1	Unitless	Real Number	First element of quaternion (and of its vector part) representing orientation between the two sets of axes.
q2	Unitless	Real Number	Second element of quaternion (and of its vector part) representing orientation between the two sets of axes.
q3	Unitless	Real Number	Third element of quaternion (and of its vector part) representing orientation between the two sets of axes.
q4	Unitless	Real Number	Fourth element of quaternion (its scalar part) representing orientation between the two sets of axes.
wx	AngleRateUnit	Real Number	First component of angular velocity vector between the two sets of axes. Represents projection of angular velocity vector onto x-axis of the selected set.
wy	AngleRateUnit	Real Number	Second component of angular velocity vector between the two sets of axes. Represents projection of angular velocity vector onto y-axis of the selected set.
wz	AngleRateUnit	Real Number	Third component of angular velocity vector between the two sets of axes. Represents projection of angular velocity vector onto z-axis of the selected set.
w mag	AngleRateUnit	Real Number	Magnitude of angular velocity vector between the two sets of axes. Represents relative speed of rotation between the two sets of axes.
RightAscension of w	AngleUnit	Real Number	Right ascension of angular velocity vector between the two sets of axes. Represents the angle between the x-axis of the selected set and projection of the angular velocity vector onto the xy-plane of the selected set. The angle is measured counterclockwise about the z-axis of the selected set.
Declination of w	AngleUnit	Real Number	Declination of angular velocity vector between the two sets of axes. Represents the angle between the angular velocity vector and its projection onto the xy-plane of the selected set. The angle is positive when the angular velocity vector is directed toward positive z-axis of the selected set.
Eigen-Angle	AngleUnit	Real Number	Angle of eigen-rotation between the two sets of axes, i.e. a single axis rotation that aligns the two sets of axes.
Eigen-Axis x	Unitless	Real Number	First component of a unit vector representing the axis of eigen-rotation between the two sets of axes. Defines instantaneous projection of the eigen-axis onto x-axis of either of the two sets of axes.
Eigen-Axis y	Unitless	Real Number	Second component of a unit vector representing the axis of eigen-rotation between the two sets of axes. Defines instantaneous projection of the eigen-axis onto y-axis of either of the two sets of axes.
Eigen-Axis z	Unitless	Real Number	Third component of a unit vector representing the axis of eigen-rotation between the two sets of axes. Defines instantaneous projection of the eigen-axis onto z-axis of either of the two sets of axes.

Name

Dimension

Type

Description

Time

DateFormat

Real Number

Time.

Sigma Xd

Rate

Real Number

Square root of the fourth diagonal component of the covariance matrix.

Sigma Yd

Rate

Real Number

Square root of the fifth diagonal component of the covariance matrix.

Sigma Zd

Rate

Real Number

Square root of the sixth diagonal component of the covariance matrix.

Correlation XdYd

Unitless

Real Number

XdYd correlation coefficient of the covariance matrix.

Correlation XdZd

Unitless

Real Number

XdZd correlation coefficient of the covariance matrix.

Correlation YdZd

Unitless

Real Number

YdZd correlation coefficient of the covariance matrix.

VelCovMtx XX

Rate Squared

Real Number

XX Component of the Velocity Covariance Matrix.

VelCovMtx YX

Rate Squared

Real Number

YX Component of the Velocity Covariance Matrix.

VelCovMtx YY

Rate Squared

Real Number

YY Component of the Velocity Covariance Matrix.

VelCovMtx ZX

Rate Squared

Real Number

ZX Component of the Velocity Covariance Matrix.

VelCovMtx ZY

Rate Squared

Real Number

ZY Component of the Velocity Covariance Matrix.

VelCovMtx ZZ

Rate Squared

Real Number

ZZ Component of the Velocity Covariance Matrix.

YPR321 yaw

AngleUnit

Real Number

Yaw angle between the two sets of axes. Defines rotation about the z-axis of the reference set, which occurs first when using 321 (or YPR) sequence in YPR angles representation.

YPR321 pitch

AngleUnit

Real Number

Pitch angle between the two sets of axes. Defines rotation about the y-axis of the reference set, which occurs second when using 321 (or YPR) sequence in YPR angles representation.

YPR321 roll

AngleUnit

Real Number

Roll angle between the two sets of axes. Defines rotation about the x-axis of the reference set, which occurs third when using 321 (or YPR) sequence in YPR angles representation.

Euler323 precession

AngleUnit

Real Number

Precession angle between the two sets of axes. Defines rotation about the z-axis of the reference set, which occurs first when using 323 sequence in Euler angles representation.

Euler323 nutation

AngleUnit

Real Number

Nutation angle between the two sets of axes. Defines rotation about the y-axis of the set rotated through precession, which occurs second when using 323 sequence in Euler angles representation.

Euler323 spin

AngleUnit

Real Number

Spin angle between the two sets of axes. Defines rotation about the z-axis of the set rotated through precession and nutation, which occurs third when using 323 sequence in Euler angles representation.

Unitless

Real Number

First element of quaternion (and of its vector part) representing orientation between the two sets of axes.

Unitless

Real Number

Second element of quaternion (and of its vector part) representing orientation between the two sets of axes.

Unitless

Real Number

Third element of quaternion (and of its vector part) representing orientation between the two sets of axes.

Unitless

Real Number

Fourth element of quaternion (its scalar part) representing orientation between the two sets of axes.

AngleRateUnit

Real Number

First component of angular velocity vector between the two sets of axes. Represents projection of angular velocity vector onto x-axis of the selected set.

AngleRateUnit

Real Number

Second component of angular velocity vector between the two sets of axes. Represents projection of angular velocity vector onto y-axis of the selected set.

AngleRateUnit

Real Number

Third component of angular velocity vector between the two sets of axes. Represents projection of angular velocity vector onto z-axis of the selected set.

w mag

AngleRateUnit

Real Number

Magnitude of angular velocity vector between the two sets of axes. Represents relative speed of rotation between the two sets of axes.

RightAscension of w

AngleUnit

Real Number

Right ascension of angular velocity vector between the two sets of axes. Represents the angle between the x-axis of the selected set and projection of the angular velocity vector onto the xy-plane of the selected set. The angle is measured counterclockwise about the z-axis of the selected set.

Declination of w

AngleUnit

Real Number

Declination of angular velocity vector between the two sets of axes. Represents the angle between the angular velocity vector and its projection onto the xy-plane of the selected set. The angle is positive when the angular velocity vector is directed toward positive z-axis of the selected set.

Eigen-Angle

AngleUnit

Real Number

Angle of eigen-rotation between the two sets of axes, i.e. a single axis rotation that aligns the two sets of axes.

Eigen-Axis x

Unitless

Real Number

First component of a unit vector representing the axis of eigen-rotation between the two sets of axes. Defines instantaneous projection of the eigen-axis onto x-axis of either of the two sets of axes.

Eigen-Axis y

Unitless

Real Number

Second component of a unit vector representing the axis of eigen-rotation between the two sets of axes. Defines instantaneous projection of the eigen-axis onto y-axis of either of the two sets of axes.

Eigen-Axis z

Unitless

Real Number

Third component of a unit vector representing the axis of eigen-rotation between the two sets of axes. Defines instantaneous projection of the eigen-axis onto z-axis of either of the two sets of axes.