Planning of an Experiment for VLBI Tracking of GNSS Satellites

As a preparation for future possible orbit determination of global navigation satellite system (GNSS) satellites by VLBI observations an initial three-station experiment was planned and performed in January 2009. The goal was to get first experience and to verify the feasibility of using the method for accurate satellite tracking. GNSS orbits related to a satellite constellation can be expressed in the Terrestrial Reference Frame. A comparison with orbit results that might be obtained by VLBI can give valuable information on how the GNSS reference frame and the VLBI reference frame are linked. We present GNSS transmitter specifications and experimental results of the observations of some GLONASS satellites together with evaluations for the expected signal strengths at telescopes. The satellite flux densities detected on the Earth s surface are very high. The narrow bandwidth of the GNSS signal partly compensates for potential problems at the receiving stations, and signal attenuation is necessary. Attempts to correlate recorded data have been performed with different software

Spacecraft VLBI and Doppler tracking: algorithms and implementation

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 operational spacecraft. We describe the software pipeline for the processing of phase referencing near-field VLBI observations and present results of the ESA Venus Express spacecraft observing campaign conducted in 2010-2011. We show that a highly accurate determination of spacecraft state-vectors is achievable with our method. The consistency of the positions indicates that an internal rms accuracy of 0.1 mas has been achieved. However, systematic effects produce offsets up to 1 mas, but can be reduced by better modelling of the troposphere and ionosphere and closer target-calibrator configurations.Comment: 10 pages, 10 figures. Astronomy and Astrophysics, accepte

First Results of Venus Express Spacecraft Observations with Wettzell

The ESA Venus Express spacecraft was observed at X-band with the Wettzell radio telescope in October-December 2009 in the framework of an assessment study of the possible contribution of the European VLBI Network to the upcoming ESA deep space missions. A major goal of these observations was to develop and test the scheduling, data capture, transfer, processing, and analysis pipeline. Recorded data were transferred from Wettzell to Metsahovi for processing, and the processed data were sent from Mets ahovi to JIVE for analysis. A turnover time of 24 hours from observations to analysis results was achieved. The high dynamic range of the detections allowed us to achieve a milliHz level of spectral resolution accuracy and to extract the phase of the spacecraft signal carrier line. Several physical parameters can be determined from these observational results with more observational data collected. Among other important results, the measured phase fluctuations of the carrier line at different time scales can be used to determine the influence of the solar wind plasma density fluctuations on the accuracy of the astrometric VLBI observations

Venus Expess radio occultation observed by PRIDE

The Planetary Radio Interferometry and Doppler Experiment (PRIDE) is a technique that can enhance the sciencereturn of planetary missions. By shadow tracking the spacecraft signal using radio telescopes from VLBI networks,the PRIDE technique provides precise open-loop Doppler and near-field VLBI observables (Duev et al. 2012,Bocanegra-Bahamon et al. 2018a) to find the radial velocity of the spacecraft and its position in the plane of thesky. This information is not only important for navigation, but it can also be used for many science applications.One such case is the study of planetary atmospheres by means of radio occultation experiments

Venus Expess radio occultation observed by PRIDE

The Planetary Radio Interferometry and Doppler Experiment (PRIDE) is a technique that can enhance the sciencereturn of planetary missions. By shadow tracking the spacecraft signal using radio telescopes from VLBI networks,the PRIDE technique provides precise open-loop Doppler and near-field VLBI observables (Duev et al. 2012,Bocanegra-Bahamon et al. 2018a) to find the radial velocity of the spacecraft and its position in the plane of thesky. This information is not only important for navigation, but it can also be used for many science applications.One such case is the study of planetary atmospheres by means of radio occultation experiments.Astrodynamics & Space Mission