Gravitational redshift test of EEP with RadioAstron from near Earth to the distance of the Moon

The Einstein Equivalence Principle (EEP) is a cornerstone of general relativity and predicts the existence of gravitational redshift. We report on new results of measuring this shift with RadioAstron (RA), a space very long baseline interferometry (VLBI) spacecraft launched into an evolving high eccentricity orbit around Earth with geocentric...

Spacecraft VLBI tracking to enhance stellar occultations astrometry of planetary satellites

Context. Stellar occultations currently provide the most accurate ground-based measurements of the positions of natural satellites (down to a few kilometres for the Galilean moons). However, when using these observations in the calculation of satellite ephemerides, the uncertainty in the planetary ephemerides dominates the error budget of the...

High spectral resolution multi-tone Spacecraft Doppler tracking software: Algorithms and implementations

We present a software package for single-dish data processing of spacecraft signals observed with VLBI-equipped radio telescopes. The Spacecraft Doppler tracking (SDtracker) software allows one to obtain topocentric frequency detections with a sub-Hz precision and reconstructed and residual phases of the carrier signal of any spacecraft or...

Planetary radio interferometry and doppler experiment (PRIDE) for planetary probes

RadioAstron gravitational redshift experiment: status update

A test of a cornerstone of general relativity, the gravitational redshift effect, is currently being conducted with the RadioAstron spacecraft, which is on a highly eccentric orbit around Earth. Using ground radio telescopes to record the spacecraft signal, synchronized to its ultra-stable on-board H-maser, we can probe the varying flow of time...

Planetary Radio Interferometry and Doppler Experiment (PRIDE) for Planetary Atmospheric Studies

RadioAstron as a target and as an instrument: Enhancing the Space VLBI mission’s scientific output

Context. The accuracy of orbit determination has a strong impact on the scientific output of the Space VLBI mission RadioAstron. Aims. The aim of this work is to improve the RadioAstron orbit reconstruction by means of sophisticated dynamical modelling of its motion in combination with multi-station Doppler tracking of the RadioAstron spacecraft...

Observations and analysis of phase scintillation of spacecraft signal on the interplanetary plasma

Aims. The phase scintillation of the European Space Agency’s Venus Express (VEX) spacecraft telemetry signal was observed at X-band (? = 3.6 cm) with a number of radio telescopes of the European Very Long Baseline Interferometry (VLBI) Network in the period 2009–2013. Methods. We found a phase fluctuation spectrum along the Venus orbit with a...

A VLBI view on the extreme scintillator J1819+3845

Scintillation of flat spectrum radio sources provides a unique instrument to study the characteristics of the electron density distribution throughout the interstellar medium as well as to study the microarcsecond structure of compact radio objects. During the course of its extreme activity, the quasar J1819+3845 has been observed with a number...

Spacecraft VLBI and Doppler tracking: Algorithms and implementation

Aims. We present the results of several multi-station Very Long Baseline Interferometry (VLBI) experiments conducted with the ESA spacecraft Venus Express as a target. To determine the true capabilities of VLBI tracking for future planetary missions in the solar system, it is necessary to demonstrate the accuracy of the method for existing...