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Current Status and Future Directions for IERS RS/PC Predictions of UT1
William Wooden Brian Luzum Nick Stamatakos


IERS RS/PC Review
· Produce daily and weekly EOP combination and prediction solutions
­ Daily EOPs produced after 1700 UTC ­ Weekly EOPs produced Thursday after 1700 UTC ­ Include AAM, GPS, SLR, and VLBI data ­ Roughly 700 users by e-mail per week ­ Roughly 40000 ftp downloads per month
· Most use the data for non-research purposes (85 to 90%) · Not all are technically skilled


Models Prediction Algorithm Time Interval

Prediction Accuracy

Input Data · Quality · Latency

Forecasts of geophysical data · AAM · OAM in the future?


Models Prediction Algorithm Time Interval

Prediction Accuracy

Input Data · Quality · Latency

Forecasts of geophysical data · AAM · OAM in the future?


Recent Changes
· AAM forecast data from National Centers for Environmental Prediction (NCEP) and U.S. Navy's Operational Global Atmospheric Prediction System (NOGAPS) was increased from 5 to 7.5 days, and, on 4 October 2007, was added to the EOP combination and prediction software · Prediction accuracy has improved beyond 5 days s i n c e th i s c h a n g e ­ Improvement by ~15%


New USNO UTGPS
· Quality of new UTGPS data
­ Uses more satellites
· Typically ~15-25 vs. ~10

­ Uses more sophisticated orbital modeling ­ Initial results look promising
· Significant improvement in UT estimates · Also improves UT1 predictions
­ Improved data quality ­ Improved predictability


Residuals of Raw UTGPS

Current UTGPS

New UTGPS


e-Transfer Intensives
· Electronically transferred (rapid) VLBI are intensives observed and processed such that they are available in less than 12 hours
­ More current than IGS Ultra observations

· Effect of rapid intensives on RS/PC on combinations and predictions
­ Analysis started 30 Sept 2007 and has continued to the present
· Only last day of combination and first (1-day) prediction analyzed

­ The finals.daily results are separated into those created with and those without rapid intensives


E-transfer Intensives (continued)
· Limited number of solutions with rapid i n te n s i v e s
­ Results are preliminary ­ Noticeable improvement in combination solution
· Roughly a factor of 2 improvement over standard solution · Estimated error of rapid intensives is roughly the same as estimated error of the intensives ­ Combination close to obtaining maximum estimated improvement

­ Prediction improvement is smaller
· Roughly 25% improvement over standard solution


E-Transfer Intensives: Preliminary Analysis
In te n s i v e Solution Number of Estimated Points Accuracy (µs) 35 25 35 544 543 91 55 124

Rapid Rapid Standard Standard

Combination Prediction Combination Prediction


E-VLBI Future
· Fortaleza is connected
­ Undergoing tests

· Kokee Park antenna will be connected soon

· Kk-Wz Intensive latency should soon be less th a n 2 4 h o u r s · Improved latency for weekly EOP experiments


Recent Improvements in EOP Data


How frequently should EOP solutions be updated?
· Currently: EOP solutions are updated daily · Near Future: Twice per day EOP solutions from IERS RS/PC · Future: Continually updated EOP solutions?


What prediction length should the algorithms be optimized for?
· Depends on users' needs
­ Most users need real-time EOP
· Most stringent accuracy requirements

­ Still need predictions to a few weeks
· Lower accuracy requirement

­ Small number of users of predictions out to a fe w y e a r s
· Ephemeris development · Leap second prediction · Lower accuracy requirement


IERS Prediction Workshop
· 19-21 October 2009 in Warsaw, Poland
­ Registration and abstract deadline 31 August

· Sessions on
­ A priori models, observations and combined solutions ­ Geophysical excitation functions and their predictions ­ EOP prediction techniques and algorithms

· Discussion and recommendations for the fu tu r e · http://www.cbk.waw.pl/EOPPW2009