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| Titel |
Quality assessment of sub-Nyquist recovery from future gravity satellite missions |
| VerfasserIn |
S. Iran Pour, T. Reubelt, M. Ellmer, N. Sneeuw |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250058350
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| Zusammenfassung |
| When using high quality sensors in future gravity missions, aliasing of the high frequency
geophysical signals to the lower frequency signals is one of the most challenging obstacles.
Two sampling theorems mainly govern the space-time sampling of a satellite-mission: (i) the
"Nyquist-theorem" β -¥ 2L (or 2M) which limits the spatial resolution (maximum
degree/order L/M), where β is the number of satellite revolutions per α nodal days, and (ii)
the "Heisenberg-theorem" Dspace ÃDtime = 2Ïα-β = 2ÏTrevolution = const. means that
the product of spatial resolution Dspace and the time-resolution Dtime is constant. These two
facts necessitate to employ more than one satellite mission to improve the temporal and
spatial resolutions simultaneously. Moreover, several studies have shown that measuring
other observable than the along track GRACE measurement improves the quality of the
solutions. Different configurations, Pendulum, Cartwheel, LISA, Helix have been
suggested for the improvement, although there are some technical concerns with their
implementations.
It is obvious that short-time solutions of the configurations are less affected by the temporal
aliasing, while they are suffering more from spatial aliasing. The purpose of this presentation
is to investigate the quality of sub-Nyquist solutions of different formation flights in
particular the dependence of such quality on the measurement duration and orbital coverage.
We suggest optimal configurations in both time and spatial domains, by the help of post
processing tools like EOF + KS test analysis and regularization. The full repeat period
solutions of these formations are studied versus their shorter time solutions by a quick
look simulation software. The sub-cycle concept is also discussed and investigated. |
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