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| Titel |
The orbital decay of the semi-major axis of LARES and the LARASE contribution to SLR measurements for applications in the fields of space geodesy and geophysics |
| VerfasserIn |
Carmen Pardini, Luciano Anselmo, David Masimo Lucchesi, Massimo Bassan, Carmelo Magnafico, Anna Maria Nobili, Roberto Peron, Giuseppe Pucacco, Ruggero Stanga, Massimo Visco |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250133601
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| Publikation (Nr.) |
 EGU/EGU2016-14231.pdf |
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| Zusammenfassung |
| The new laser-ranged satellite LARES (LAser RElativity Satellite) is expected to provide
new refined measurements of relativistic physics as well as significant contributions to
space geodesy and geophysics. The very low area-to-mass ratio of this passive and
dense satellite was chosen to reduce as much as possible the disturbing effects due
to the non-gravitational perturbations in order to compensate for its much lower
altitude with respect to the two older LAGEOS (LAser GEOdynamic Satellite)
satellites, currently the best tracked satellites of the International Laser Ranging Service
network.
Indeed, because of its height, about 1450 km with respect to the 5900 km of the two
LAGEOS, LARES is subject to a much stronger perturbation provoked by the neutral drag
than that on the two LAGEOS.
From a Precise Orbit Determination (POD) of LARES over a time span of about 3.7 years
we have been able to measure an orbital decay in the residuals of its semi-major axis of about
1 m/yr, that corresponds to a transversal mean acceleration of about –1.457×10−11 m/s2.
This POD has been obtained analyzing LARES normal points with the GEODYN II
(NASA/GSFC) software. Neither the neutral drag nor the thermal effects have been included
in the dynamical models of GEODYN II.
By means of a modified version of the SATellite Reentry Analysis Program
(SATRAP) of ISTI/CNR, the neutral drag perturbation has been computed over
the same time span accounting for the measured decay and considering the real
evolution of the solar and geomagnetic activities for several atmospheric models. In
particular, assuming as reference for the unmodeled transversal acceleration due to the
neutral atmosphere the above value, the drag coefficient estimated by SATRAP is
comparable to the average value estimated by GEODYN II in a least square fit of the
tracking data. This means that the current best models developed for the atmosphere
behavior are able to account for the observed decay, within their errors and range of
applicability.
A further analysis is needed in order to extract from the observed decay a possible smaller
contribution related with other unmodeled effects, as the thermal ones, acting on the
satellite. In this context it will be necessary to fix the contribution of the signature of
the drag and of the thermal effects in the residuals of the other orbital elements of
LARES.
This study falls within the activities of the LARASE (LAser RAnged Satellites
Experiment) research program. LARASE main goal is to provide new and refined
measurements of the relativistic effects acting on the orbit of the two LAGEOS and LARES
satellites.
In particular, a major point of these activities is to provide a final robust and reliable
error budget for the main systematic effects of gravitational and non-gravitational
origin.
Therefore, a special attention is devoted to the modeling of the non-gravitational
perturbations acting on these passive laser-ranged satellites. Improvements in their modeling
will be useful both in the field of general relativity measurements and in those of space
geodesy and geophysical applications. |
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