Data Provider Groups | Data Provider Elements
ICRF Angles
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.Available for these objects: Scenario
Type: Time-varying data.
Availability: Reports | Graphs | Dynamic Displays | Strip Charts
Data Provider Groups
| Name | Description |
|---|---|
| IAU 2000 | Values computed using the IAU2000A nutation theory and the IAU1976 precession theory with rate corrections. Based on IERS Tech Note 32. |
| IAU 2006 | Values computed using the IAU2000A theory for nutation (as adjusted) and the P03 theory of precession. Based on IERS Tech Notes 32 and 36. |
Data Provider Elements
| Name | Dimension | Type | Description |
|---|---|---|---|
| Time | Date | Real Number or Text | Time. |
| MJD | Unitless | Real Number | Modified Julian Date (UTC time scale). |
| UT1MJD | Unitless | Real Number | Modified Julian Date (UT1 time scale). |
| X (Series) | Angle | Real Number or Text | The X direction cosine of the CIP unit vector, evaluated using the series expansion available from the applicable IERS Tech Note. For convenience, the value is expressed as if it were an angle. |
| Y (Series) | Angle | Real Number or Text | The Y direction cosine of the CIP unit vector, evaluated using the series expansion available from the applicable IERS Tech Note. For convenience, the value is expressed as if it were an angle. |
| S (Series) | Angle | Real Number or Text | The CIO locator, evaluated using the series expansion available from the applicable IERS Tech Note, and the values of X (Series) and Y(Series). |
| X (Interpolated) | Angle | Real Number or Text | The X direction cosine of the CIP unit vector, evaluated using interpolation of a table of X values from 1975-2050. |
| Y (Interpolated) | Angle | Real Number or Text | The Y direction cosine of the CIP unit vector, evaluated using interpolation of a table of Y values from 1975-2050. |
| S (Interpolated) | Angle | Real Number or Text | The CIO locator, evaluated using interpolation of a table of S values from 1975-2050. |
| X (Delta Psi Eps) | Angle | Real Number or Text | The X direction cosine of the CIP unit vector, evaluated by computing the Bias Precession Nutation (BPN) matrix using expressions dependent on Delta Psi and Delta Eps. |
| Y (Delta Psi Eps) | Angle | Real Number or Text | The Y direction cosine of the CIP unit vector, evaluated by computing the Bias Precession Nutation (BPN) matrix using expressions dependent on Delta Psi and Delta Eps. |
| S (Delta Psi Eps) | Angle | Real Number or Text | The CIO locator, evaluated using the series expansion available from IERS Tech Note 32, and the values of X (Delta Psi Eps) and Y(Delta Psi Eps). |
| X (Series - Interp) | Angle | Real Number or Text | The difference between X (Series) and X (Interpolated) values. |
| Y (Series - Interp) | Angle | Real Number or Text | The difference between X (Series) and X (Interpolated) values. |
| S (Series - Interp) | Angle | Real Number or Text | The difference in S between that value computed using the IERS series approximation minus the value found through interpolation. |
| X (Delta Psi Eps - Interp) | Angle | Real Number or Text | The difference between X (Delta Psi Eps) and X (Interpolated) values. |
| Y (Delta Psi Eps - Interp) | Angle | Real Number or Text | The difference between Y (Delta Psi Eps) and Y (Interpolated) values. |
| S (Delta Psi Eps - Interp) | Angle | Real Number or Text | The difference between S (Delta Psi Eps) and S (Interpolated) values. |
| Angle Diff (Series - Interp) | Angle | Real Number or Text | The angular difference between the frames realized using X, Y, S computed from the series expansion and X, Y, S computed using interpolation. |
| Angle Diff (Delta Psi Eps - Interp) | Angle | Real Number or Text | The angular difference between the frames realized using X, Y, S computed from the Delta Psi and Delta Eps and X, Y, S computed using interpolation. |
| Delta Psi | Angle | Real Number or Text | Variable associated with the definition of the IAU2000A nutation theory. |
| Delta Eps | Angle | Real Number or Text | Variable associated with the definition of the IAU2000A nutation theory. |
| Earth Rotation Angle | Angle | Real Number or Text | The rotation along the intermediate equator between the CIO and terrestrial origin. |
| dX | Angle | Real Number or Text | The correction to X when using the ICRF theory. Published as part of EOP data. |
| dY | Angle | Real Number or Text | The correction to Y when using the ICRF theory. Published as part of EOP data. |
| Delta Delta Psi | Angle | Real Number or Text | The correction to Delta Psi for converting between J2000 and the ICRF reference frame using the FK5 IAU76 theory. Published as part of EOP data. |
| Delta Delta Eps | Angle | Real Number or Text | The correction to Delta Epsilon for converting between J2000 and the ICRF reference frame using the FK5 IAU76 theory. Published as part of EOP data. |
| Pole Wander X | Angle | Real Number or Text | Small angle related to changes in orientation of the earth pole due to continental drift. |
| Pole Wander Y | Angle | Real Number or Text | Small angle related to changes in orientation of the earth pole due to continental drift. |
| UT1-UTC | Time | Real Number | The difference between Universal Time (UT1) and Coordinated Universal Time (UTC). |
| TDTTimeSinceJ2000 | Time | Real Number | Duration (in TDT seconds) since the J2000 epoch. |
| UT1TimeSinceJ2000 | Time | Real Number | Duration (in UT1 seconds) since the J2000 epoch. |
| TDTMinusUT1 | Time | Real Number | The difference between TDTTimeSinceJ2000 and UT1TimeSinceJ2000. |