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DETERMINATION OF THE GRAVITY FIELD OVER

NORWEGIAN TERRITORIES

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GRAVNOR: DETERMINATION OF THE GRAVITY FIELD OVER NORWEGIAN TERRITORIES USING GOCE DATA AND SPACE GEODESY SOFTWARE GEOSAT

E. Mysen (Norwegian Mapping Authority, NMA)

P.H. Andersen (Norwegian Defence Research Establishment, NDRE)

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SPACE GEODESY SOFTWARE GEOSAT

25 years at Norwegian Defence Research Establishment

GPS, VLBI, SLR simultaneously at observation level Inter technique calibration

Stochastic parameter evolution between days (arcs)Utilization of parameter statistics

Accelerometry: GOCE

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DETERMINATION OF LOCAL GRAVITY (NORWAY)

Norwegian Mapping Authority (NMA):Contribute to the determination of climate parametersDetermine the cm geoidTransfer of GEOSAT competence from NDRE to NMA

Why local analysis?ESA -> SH expansion: truncation issues (40,000 parameters)May still be information left in accelerometer signal Norway gravitationally “rough”

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STRATEGY

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SINGLE ACCELEROMETER OBSERVATIONS

Benefits:Less susceptible to accelerometer failureAlgorithms applicable to other missions like GRACE

Disadvantage:Non-gravitational force has to be modeled as part of gravity field determination

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ACCELEROMETER OBSERVATION EQUATION

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Output of accelerometer j:

True acceleration:

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ATTITUDE CORRECTIONS

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GRF 2 CRF rotation matrix:

Indirect effect on true acceleration:

:

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DYNAMIC ORBIT DETERMINATION/CALIBRATION

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Computation of orbit:

Expression for non-gravitational force D dependent instrument imperfections?

Accelerometer orbit-GPS orbit=instrument imperfections

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Estimate of D for Dynamic Orbit Determination

LSQ applied to accelerometer observations with D as only unknown:

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CALIBRATION BY DOD

Issue: Along-track scale factor not well determined from DOD alone due to along-track DFC (Visser, 2009)

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Solution?:

Simultaneous determination of orbit and local gravity field

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PARALLELL AND FUTURE

Altimetry: Sea level & ocean currents (NMA)

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GRACE

WEAKNESSES OF GRAVNOR???