2,661 research outputs found
Experimental tests of relativistic gravitation theories
Experimental tests were studied for determining the potential uses of future deep space missions in studies of relativistic gravity. The extensions to the parametrized post-Newtonian framework to take explicit account of the solar system's center of mass relative to the mean rest frame of the Universe is reported. Discoveries reported include the Machian effects of motion relative to the universal rest frame. Summaries of the JPL research are included
Signatures of the Martian rotation parameters in the Doppler and range observables
The position of a Martian lander is affected by different aspects of Mars'
rotational motions: the nutations, the precession, the length-of-day variations
and the polar motion. These various motions have a different signature in a
Doppler observable between the Earth and a lander on Mars' surface. Knowing the
correlations between these signatures and the moments when these signatures are
not null during one day or on a longer timescale is important to identify
strategies that maximize the geophysical return of observations with a geodesy
experiment, in particular for the ones on-board the future NASA InSight or
ESA-Roscosmos ExoMars2020 missions.
We provide first-order formulations of the signature of the rotation
parameters in the Doppler and range observables. These expressions are
functions of the diurnal rotation of Mars, the lander position, the planet
radius and the rotation parameter. Additionally, the nutation signature in the
Doppler observable is proportional to the Earth declination with respect to
Mars.
For a lander on Mars close to the equator, the motions with the largest
signature in the Doppler observable are due to the length-of-day variations,
the precession rate and the rigid nutations. The polar motion and the liquid
core signatures have a much smaller amplitude. For a lander closer to the pole,
the polar motion signature is enhanced while the other signatures decrease.
We also numerically evaluate the amplitudes of the rotation parameters
signature in the Doppler observable for landers on other planets or moons.Comment: 30 pages 7 figures, In press PS
Mariner Mars 1971 optical navigation demonstration
The feasibility of using a combination of spacecraft-based optical data and earth-based Doppler data to perform near-real-time approach navigation was demonstrated by the Mariner Mars 71 Project. The important findings, conclusions, and recommendations are documented. A summary along with publications and papers giving additional details on the objectives of the demonstration are provided. Instrument calibration and performance as well as navigation and science results are reported
Constraining the Nordtvedt parameter with the BepiColombo Radioscience experiment
BepiColombo is a joint ESA/JAXA mission to Mercury with challenging
objectives regarding geophysics, geodesy and fundamental physics. The Mercury
Orbiter Radioscience Experiment (MORE) is one of the on-board experiments,
including three different but linked experiments: gravimetry, rotation and
relativity. The aim of the relativity experiment is the measurement of the
post-Newtonian parameters. Thanks to accurate tracking between Earth and
spacecraft, the results are expected to be very precise. However, the outcomes
of the experiment strictly depends on our "knowledge" about solar system:
ephemerides, number of bodies (planets, satellites and asteroids) and their
masses. In this paper we describe a semi-analytic model used to perform a
covariance analysis to quantify the effects, on the relativity experiment, due
to the uncertainties of solar system bodies parameters. In particular, our
attention is focused on the Nordtvedt parameter used to parametrize the
strong equivalence principle violation. After our analysis we estimated
which is about 1~order of magnitude
larger than the "ideal" case where masses of planets and asteroids have no
errors. The current value, obtained from ground based experiments and lunar
laser ranging measurements, is .
Therefore, we conclude that, even in presence of uncertainties on solar system
parameters, the measurement of by MORE can improve the current precision
of about 1~order of magnitude
JPL bibliography 39-12 - Prerelease for December 1970
Bibliography of technical reports on scientific and engineering studies, December 197
NASA Innovative Advanced Concepts (NIAC) Phase 1 Final Report: Venus Landsailer Zephyr
Imagine sailing across the hot plains of Venus! A design for a craft to do just this was completed by the COncurrent Multidisciplinary Preliminary Assessment of Space Systems (COMPASS) Team for the NASA Innovative Advanced Concepts (NIAC) project. The robotic craft could explore over 30 km of surface of Venus, driven by the power of the wind
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