NATIONAL REPORT OF THE FEDERAL REPUBLIC OF ... - IAG Office

46 Commission 2 – Gravity Field
Development of sensor analysis and gravity
field determination, validation and calibration
techniques
In Munich, a simulation tool for the integrated sensor
analysis of CHAMP, GRACE and GOCE instrument data
has been developed, optimized and used to analyze real
CHAMP and GRACE mission data (FROMMKNECHT et al.
(2003, 2006), FACKLER (2005)). The combination of star
sensor and accelerometer data was investigated by OBERN-
DORFER and MÜLLER (2003). WERMUTH et al. (2006) performed
GOCE mission simulation and semi-analytical
gravity field analysis for SGG and SST data.
The determination of highly-precise orbits for the Low
Earth Orbiters based upon GPS and SLR observations is
an important prerequisite for gravity field recovery.
Dynamic model orbits from combined LEO and GPS data
were generated by KÖNIG et al. (2005) while kinematic
precise orbit determination was described in SVEHLA and
ROTHACHER (2005) and SVEHLA and FÖLDVARY (2006).
KROES et al. (2005) and KOHLHASE et al. (2006) investigated
precise GRACE baseline determination using GPS
data.
While the operational global gravity field products of the
CHAMP and GRACE Science Data Systems at GFZ
Potsdam are based on dynamical orbit analysis of daily arcs
(REIGBER et al. (2003a, 2003b, 2003c, 2005), SCHMIDT et
al. (2006)) other groups started to analyse and validate the
measurement data with alternative methods and also on
regional scales. ILK et al. (2005) and MAYER-GÜRR et al.
(2005, 2006) performed gravity field recovery and validation
by analysis of short arcs of CHAMP and GRACE. The
usefulness of the energy balance method for gravity field
determination and validation was shown by several authors
(ILK (2003), VISSER et al. (2003), ILK and LÖCHER (2005),
FÖLDVARY et al. (2005), GERLACH et al. (2003a, 2003b),
REUBELT et al. (2006), or LÖCHER and ILK (2007)).
Regional gravity field solutions based on spherical wavelet
and base functions were presented by ILK et al. (2007) and
SCHMIDT et al (2006, 2007). The concept of the gravity
space approach was demonstrated by AUSTEN and KELLER
(2007). FENGLER et al. (2004a, 2004b) derived CHAMP
and GRACE gravity field solutions by multiscale methods.
Gravitational field modelling from CHAMP-ephemeredes
by harmonic splines and fast multipole techniques was
described by GLÖCKNER (2003). The modelling of regional
and temporal gravity field solutions using wavelet
modelling was shown by FENGLER et al. (2005, 2007) and
FREEDEN and SCHREINER (2005). Different gravity field
determination procedures applied to CHAMP data were
compared by WERMUTH et al. (2004). Sneeuw reported on
the space-wise, time-wise, torus and Rosborough representation
in gravity field modelling.
BOSCH (2005) used the EIGEN-GRACE02S gravity field
model to investigate defectiveness of marine gravity data
and KLOKOCNIK et al. (2005) evaluated the accuracy of the
EIGEN-1S and -2 CHAMP derived gravity field models
by satellite crossover altimetry. A high resolution global
gravity field model from combination of CHAMP and
GRACE satellite mission and surface data called EIGEN-
CG01C was presented by REIGBER et al. (2006).
Preparations for GOCE
Preparations for GOCE data analysis have been performed
on various levels. DENKER (2003), DIETRICH et al. (2004),
MÜLLER et al. (2003, 2004), BOUMAN et al. (2005), TOTH
et al. (2005) and JARECKI et al. (2006) investigated methods
to calibrate and validate the GOCE gradiometer data. The
development and status of the GOCE High Level Processing
Facility (HPF), which is in charge for the GOCE gravity
field determination was described in RUMMEL et al. (2004),
GRUBER et al. (2006) and KOOP et al. (2007). PAIL et al.
(2007a, 2007b) developed tools for HPF GOCE quick-look
gravity field analysis, which is designed for monitoring the
overall GOCE performance as part of the HPF activities.
The correct use of GOCE level-2 products was treated by
GRUBER et al. (2007). The German GOCE project bureau
at Technical University of Munich contributed since 2001
to a coordinated preparation of GOCE data analysis and
applications in Earth sciences.
Outcome and further Planning
As a result of the enormous success of CHAMP and
GRACE and in expectation of the GOCE mission results
a Special Priority Program SPP “Mass Transport and Mass
Distribution in the Earth System” has been proposed by ILK
et al. (2004, 2005) and finally accepted by the German
Research Foundation DFG for the period 2006 till 2011.
FLURY and RUMMEL (2004) introduced the goals of the SPP
at a GOCE user workshop.
The need and design of future follow-on gravity field
missions to derive continuous and highly precise time series
of gravity field variations for Earth system monitoring was
discussed in BEUTLER et al. (2003), AGUIRRE-MARTINEC
and SNEEUW (2003), FLURY and RUMMEL (2005a, 2005b)
and SNEEUW et al. (2005).
References
AGUIRRE-MARTINEC M., SNEEUW N.; Needs and tools for future
gravity measuring missions; Space Science Reviews,
Kluwer Academic Publishers, Vol. 108, 1-2, p. 409-416,
2003
AUSTEN G., KELLER W.; Numerical implementation of the gravity
space approach – proof of concept; IAG Symposia Processings
No. 130, Dynamic Planet, Ed. Tregoning, Rizos,
Springer Verlag, 2007
BEUTLER, G., DRINKWATER M., RUMMEL R. VON STEIGER R.;
Earth Gravity Field from Space: from Sensors to Earth
Sciences. Space Science Reviews, 108:1-2. Kluwer, Dordrecht,
2003
BOSCH W.; Using the EIGEN-GRACE02S gravity field to investigate
defectiveness of marine gravity data; IAG Symposia
Proceedings, Vol. 129, Ed. Jekeli, Bastos, Fernades,
Springer Verlag, 2005
BOUMAN J., KOOP R., HAAGMANS R., MÜLLER J., SNEEUW N.,
TSCHERNING C.C., VISSER P.; Calibration and validation
of GOCE gravity gradients; in: IAG Symposia Proceedings