 |
| Titel |
Gradient estimation using configurations of two or three spacecraft |
| VerfasserIn |
J. Vogt, E. Sorbalo, M. He, A. Blagau |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
0992-7689
|
| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 31, no. 11 ; Nr. 31, no. 11 (2013-11-05), S.1913-1927 |
| Datensatznummer |
250086140
|
| Publikation (Nr.) |
 copernicus.org/angeo-31-1913-2013.pdf |
|
|
|
|
|
| Zusammenfassung |
| The forthcoming three-satellite mission Swarm will allow us to investigate
plasma processes and phenomena in the upper ionosphere from an in-situ
multi-spacecraft perspective. Since with less than four points in space the
spatiotemporal ambiguity cannot be resolved fully, analysis tools for
estimating spatial gradients, wave vectors, or boundary parameters need to
utilise additional information such as geometrical or dynamical constraints.
This report deals with gradient estimation where the planar component is
constructed using instantaneous three-point observations or, for quasi-static
structures, by means of measurements along the orbits of two close
spacecraft. A new least squares (LS) gradient estimator for the latter case
is compared with existing finite difference (FD) schemes and also with a
three-point LS technique. All available techniques are presented in a common
framework to facilitate error analyses and consistency checks, and to show
how arbitrary combinations of planar gradient estimators and constraints can
be formed. The accuracy of LS and FD planar gradient estimators is assessed
in terms of prescribed and adjustable discretization parameters to optimise
their performance along the satellite orbits. Furthermore, we discuss the
implications of imperfect constraint equations for error propagation, and
address the effects of sub-scale structures. The two-spacecraft LS scheme is
demonstrated using Cluster FGM measurements at a planar and essentially
force-free plasma boundary in the solar wind where all three different types
of constraints to construct out-of-plane derivatives can be applied. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|