The present Editorial introduces the Special Issue dedicated by the journal Universe to the
General Theory of Relativity, the beautiful theory of gravitation of Einstein, a century after its …

The lunar laser ranging (LLR) technique is based on the two-way time-of-flight of laser
pulses from an earth station to the retroreflectors that are located on the surface of the moon …

In the current and future trend towards smaller satellite missions, the development of a
simple and reliable propulsion system with performance and characteristics in line with the …

This work bibliographically reviews several aspects that relate to a new concept of geodesy,
where the principles of relativity play a leading role. Ongoing improvements, especially in …

Abstract The Frequency Difference of Arrival (FDOA) equations derived in this paper are
intended to increase the standard accuracy of the Low Earth Orbit (LEO) satellites dedicated …

The development of a Lunar and Satellite Laser Ranger at the Hartebeesthoek Radio
Astronomy Observatory, South Africa, in collaboration with the Observatoire de la Côte …

Spacecraft propagation tools describe the motion of near-Earth objects and interplanetary
probes using Newton's theory of gravity supplemented with the approximate general …

The equations of motion derived in this paper are aimed to determine according to the post-
Newtonian framework the relative motion of Earth satellites with respect to inertial guided …

It has recently been proposed to combine the node drifts of the future constellation of 27
Galileo spacecraft together with those of the existing Laser Geodynamics Satellites …

Hydrogen maser frequency standards are commonly utilised in various space geodetic
techniques such as Very Long Baseline Interferometry (VLBI) as local reference clocks. The …