Ramesh GOVIND and John DAWSON

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ILRS AWG Pilot Project POSEOP

• Ramesh GOVIND and John DAWSON

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ILRS AWG Pilot Project POSEOP

• Analysis for
• Lageos1, Lageos2,
• Etalon1, Etalon2
• ILRS AWG options A, B1 and B2

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Changes Implemented

• use of the IERS2000 diurnal and semi-diurnal
  Earth Orientation model
• a revised time and range bias estimation scheme
• use of the Mendes FCUL mapping function for
  atmospheric refraction

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Data Set

• Only stations that observed 30 or more
  observations during each 28 day solution were
  included in the analysis.

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Series A Global SLR data.
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Series B Global SLR data.
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Analysis Procedure
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Multi-Arc NEQ Combination
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Computation Procedure

• Data Weighting
• 1.0 CM GOOD STATIONS,
• 5.0 CM POOR STATIONS
• Centre of Mass
• L1 AND L2 0.251
• E1 AND E2 0.558 FOR ALL STATIONS

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Estimated Parameters

• STATION COORDINATES
• DAILY X, Y AND TAI-UT1 RATES
• LAGEOS 1 AND 2
• SATELLITE ELEMENTS PER 28 DAY ARC
• SOLAR RADIATION PRESSURE SCALE (once per arc)
• ALONG TRACK ACCELERATION CONSTANT AND
  ONCE-PER-REVOLUTION SINE/COSINE EVERY 7 DAYS
• CROSS TRACK ONCE-PER-REVOLUTION SINE/COSINE
  EVERY 7 DAYS RANGE
  BIAS PER STATION EVERY 7 DAYS

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Estimated Parameters

• ETALON 1 AND 2
• SATELLITE ELEMENTS PER 28 DAY ARC
• SOLAR RADIATION PRESSURE SCALE FACTOR EVERY
  28 DAYS
• ALONG TRACK ACCELERATION CONSTANT AND
  ONCE-PER-REVOLUTION SINE/COSINE EVERY 28 DAYS
• CROSS TRACK ONCE-PER-REVOLUTION SINE/COSINE
  EVERY 28 DAYS

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CONSTRAINTS

• ORBIT UNCONSTRAINED
• RANGE BIAS 1 M
• X/Y POLE 20 MAS, UT 2 MS
• X/Y POLE RATE 10 MAS/DAY, LOD 0.2 MS
• STATION COORDINATES 1 M OR 10 M

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Work in progress

• upgrade of our computation, combination and SINEX
  output software to include the ability to
  estimate and output EOP rates, i.e. xpole/ypole
  rate and Length of Day (LOD)

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CONCLUSIONS

• No significant improvement in station coordinate
  solution with the inclusion of sparse/limited
  Etalon data. Lageos dominate the solution.
• Marginal improvement in the EOP solution with the
  inclusion of the Etalon data -- more stations /
  more data still required to see any impact.