Dennis D. McCarthy Elements of Prediction

Why are we here? IERS Working Group on Predictions IERS Working Group on Predictions Definitive user requirements Definitive user requirements Comprehensive look at prediction methods Comprehensive look at prediction methods Comprehensive look at new data sets Comprehensive look at new data sets IERS Technical Note describing current state-of- the-art EOP prediction including requirements, methods, and data set information content IERS Technical Note describing current state-of- the-art EOP prediction including requirements, methods, and data set information content Workshop Goal: Workshop Goal: Provide specific recommendations to improve current techniques/IERS Products

History of Earth Orientation Prediction USNO began publishing predictions weekly in April, 1979 USNO began publishing predictions weekly in April, 1979 Originally designed to improve Doppler satellite geodesy Originally designed to improve Doppler satellite geodesy Original goal was 0.03” thirty days in advance Original goal was 0.03” thirty days in advance

Accuracy In the next 30 years…? 30 Years Later

Input Data Combination of Observations Astronomical Astronomical VLBI VLBI GPS GPS SLR/LLR SLR/LLR DORIS DORIS Meteorological Meteorological Oceanographic? Oceanographic? Geophysical? Geophysical? Forecasts Meteorological Meteorological Oceanographic? Oceanographic?

Accuracy In the next 30 years…? 30 Years Later

Limiting Factors Systematic Errors Systematic Errors System stability System stability Data availability Data availability Latency Latency Constraints built into the input data Constraints built into the input data Formats Formats

The Quest for the Holy Grail "The High Mysterious Call" from: Rolleston, T. W. Parsifal, or the Legend of the Holy Grail retold from Ancient Sources The Future?  Develop robust software to  Combine data at the observation level  Adapt to changing systems  Accept new contributions  Accept streaming input observations  Use geophysical data?  Provide sub-daily EOPs  Provide real time analysis  Be interactive  Maintain reference system stability

The Beginning of the Quest McCarthy, D. D., 1981, “On the adoption of a terrestrial reference frame,” Reference coordinate systems for earth dynamics; Proceedings of the Fifty-sixth IAU Colloquium, Warsaw, Poland, September 8-12, McCarthy, D. D. and Babcock, A. K., 1985, “The U.S. Naval Observatory C.O.R.E. (Combined solution for the orientation of the Earth) solution during project MERIT,” in Earth rotation and the terrestrial reference frame, I. I. Mueller (ed.).

What should IERS provide to users? Develop Model Algorithm ? Test Implement Model Plots Daily values Sub-daily values Mathematical Formulas Annual Values Collect Information User needs Research Available Knowledge Collect and analyze new observations Disseminate Products Bulletins Stored data

What Should IERS Provide to Users? What do users want? What do users want? Survey questionnaires Survey questionnaires Product usage Product usage Interactive feedback Interactive feedback What will users want in the future? What will users want in the future? Prediction of UT1-UTC will be more important if leap second disappears in 2019 Prediction of UT1-UTC will be more important if leap second disappears in 2019 Who will be the users of the future? Who will be the users of the future? What systems will be developed that require predictions? What systems will be developed that require predictions? Dissemination processes in the future Dissemination processes in the future

General Requirements One unique set of IERS prediction products Easily accessible User friendly Reliable Meets users’ needs for Accuracy Update frequency Spacing Prediction interval Metadata

Collect Information Prograde Annual Wobble Prograde Semi-annual Wobble Atmospheric Tides Precession Nutations Free Core Nutation Frequency in the Terrestrial Reference Frame (cycles per day) Frequency in the Celestial Reference Frame (cycles per day) POLAR MOTION NUTATION Power Chandler Wobble Frequency Power annual semi -annual southern oscillation quasi-biennial oscillation day oscillations monthly fortnightly atmospheric tides decade fluctuations (from core?) atmospheric modes solid Earth and ocean tides 0.1 year year -1 1 year month -1

Observational Information Survey of suitable observational data Survey of suitable observational data Astronomical Astronomical Meteorological Meteorological Oceanographic Oceanographic Hydrological Hydrological Geophysical Geophysical Assessments of likely future observational data Assessments of likely future observational data

Develop Model Depends on prediction interval and nature of prediction product Depends on prediction interval and nature of prediction product Prediction for next 5 days? 30 days? decade? Prediction for next 5 days? 30 days? decade? Product provided hourly? daily? annually? Product provided hourly? daily? annually? Statistical / physical ? Statistical / physical ? Qualities Qualities Accuracy Accuracy Stability over time Stability over time Compatible with data likely to be available Compatible with data likely to be available

Develop Model

Implement Model Tables of data Tables of data Daily? Daily? Sub-daily? Sub-daily? Quarterly? Quarterly? Annually? Annually? Mathematical models/formulas? Mathematical models/formulas? Rotation matrix elements Rotation matrix elements Updated Updated As data become available? As data become available? Hourly? Hourly? Daily? Daily?

Disseminate Products On-demand On-demand Web site Web site Bulletins Bulletins

The Future: Predictions about Predictions Increasing demand for near real- time information Improved observational data

Improved Earth Orientation Observations Densified geodetic networks Improved analysis models Improved celestial reference frame CIP TIO CIO Earth Rotation Angle

The Future: Predictions about Predictions Increasing demand for near real- time information Improved observational data Increased geophysical input

Increased Geophysical Input Improved meteorological forecast data o Densified observational networks o Longer forecast intervals Oceanographic data Hydrological data Additional geophysical data?

The Future: Predictions about Predictions Increasing demand for near real- time information Improved observational data Increased geophysical input Near real-time observations

Near Real-time Observations GNSS VLBI Geophysical

The Future: Predictions about Predictions Increasing demand for near real- time information Improved observational data Increased geophysical input Near real-time observations Changes to forecast model(s)

Changes to Forecast Model(s) Adapt to Adapt to User needs User needs Data accuracy Data accuracy Data latency Data latency Multiple models may be required Multiple models may be required

The Future: Predictions about Predictions Increasing demand for near real- time information Improved observational data Increased geophysical input Near real-time observations Changes to forecast model(s) Near real-time product updates Sub-daily spacing New Products

High quality with prediction intervals < few days Lesser quality for prediction intervals < 2 weeks Low quality quarterly predictions for special users Interactive NTP UT1

Next Steps Next Steps Establish user needs Establish user needs Support oceanographic data Support oceanographic data Develop models to meet user needs, data accuracy and latency Develop models to meet user needs, data accuracy and latency Let’s Get Started Workshop Goal: Provide specific recommendations to improve current techniques/IERS Products