arXiv subjects

Jasper Edwards

Publications and source records attributed to Jasper Edwards.

5 recordsLinked to original sources

arXiv2026

Preparation of a celestial field for precise VLBI observations of the JUICE spacecraft: a test case of the Venus flyby

The Jupiter Icy Moons Explorer mission, launched in 2023, is on its way to the Jovian system, to arrive in 2031. The Planetary Radio Interferometry and Doppler Experiment performs radio astronomical observations of the spacecraft already in its interplanetary cruise phase. Since the sky density of potential compact radio sources suitable as phase-reference calibrators in very long baseline interferometry observations is low, densifying the celestial reference frame along the Ecliptic is an essential task in support of JUICE. In preparation for the JUICE gravity assist manoeuvre at Venus in August 2025, to support the accurate reconstruction of the spacecraft state vector, we selected in-beam calibrator source candidates along the JUICE trajectory. Additionally, we attempted to link known nearby bright compact reference sources from the Radio Fundamental Catalog to the International Celestial Reference Frame. We performed nodding-style phase-referencing VLBI observations with the European VLBI Network at 8.4GHz, targeting nine in-beam calibrator candidate and three RFC sources in the celestial vicinity of JUICE's trajectory during its Venus flyby. We linked their positions to nearby ICRF sources by means of relative astrometry. Four of the ICC targets and all RFC sources were detected and imaged with the EVN, and their coordinates determined with typically sub-mas precision. Although none of the targeted ICC sources proved suitable as VLBI phase-reference calibrators because of being too faint or resolved, their newly-determined positions and flux densities could in principle be used to verify the detection of the spacecraft at the time of the actual flyby around Venus. During the detailed analysis of the ICC targets, we found that the structure of one of them, J0843+1826 is resolved on mas scale, and the other one, J0843+1814 is a young radio galaxy, likely a member of a cluster.

astro-ph.IM↗

arXiv2026

VLBI Tracking of the JUICE Mission: Two Years of Cruise Phase Operations and Performance Analysis

The JUpiter ICy moons Explorer (JUICE) mission, launched by the European Space Agency (ESA) in April 2023, represents one of the most ambitious deep space exploration endeavours targeting Jupiter's icy moons. This paper presents results from the Very Long Baseline Interferometry (VLBI) radio telescope tracking conducted by the University of Tasmania during the first two years of JUICE's cruise phase operations. We have conducted over 100 tracking sessions capturing the spacecraft across different orbital regimes as JUICE progresses through its complex cruise trajectory towards Jupiter. Our analysis focuses on three key areas: Doppler residual characterisation, mission performance indicator extraction, and solar wind scintillation pattern analysis (including space weather forecasting). UTAS measurements demonstrate the enhanced capabilities that VLBI networks provide for deep space mission support, particularly for precision orbit determination and spacecraft health diagnosis. The results showcase the UTAS VLBI array as a valuable complement to traditional tracking infrastructure, offering Southern Hemisphere coverage and enhanced geometric diversity for deep space missions.

physics.space-ph↗

arXiv2025

An Analysis of a Coronal Mass Ejection Leading Edge by Means of Multi-Spacecraft-in-Beam Phase Scintillation

A Coronal Mass Ejection (CME) was detected crossing the radio signals transmitted by the Mars Express (MEX) and Tianwen-1 (TIW) spacecraft at a solar elongation of $4.4^{o}$. The impact of the CME was clearly identifiable in the spacecraft signal SNR, Doppler noise and phase residuals observed at the University of Tasmania's Very Long Baseline Interferometry (VLBI) antenna in Ceduna, South Australia. The residual phases observed from the spacecraft were highly correlated with each other during the transit of the CME across the radio ray-path despite the spacecraft signals having substantially different Doppler trends. We analyse the auto- and cross-correlations between the spacecraft phase residuals, finding time-lags ranging between 3.18-14.43 seconds depending on whether the imprinted fluctuations were stronger on the uplink or the downlink radio ray-paths. We also examine the temporal evolution of the phase fluctuations to probe the finer structure of the CME and demonstrate that there was a clear difference in the turbulence regime of the CME leading edge and the background solar wind conditions several hours prior to the CME radio occultation. Finally, autocorrelation of the MEX two-way radio Doppler noise data from Ceduna and closed-loop Doppler data from ESA's New Norcia ground station antenna were used to constrain the location of the CME impact along the radio ray-path \add{to a region 0.2 AU from the Sun, at a heliospheric longitude consistent with CME origin at the Sun. The results presented demonstrate the potential of the multi-spacecraft-in-beam technique for studying CME structures in great detail, and providing measurements that complement the capabilities of future solar monitoring instruments.

astro-ph.SR↗

arXiv2025

Implementing the PRIDE technique for the JUICE mission at the University of Tasmania

The Jupiter Icy Moons Explorer (JUICE) spacecraft is a European Space Agency (ESA) mission to study the Jovian system, currently undergoing an eight-year cruise phase. The Planetary Radio Interferometric and Doppler Experiment (PRIDE) is one of eleven experiments contributing to the JUICE mission. PRIDE aims to conduct radio science experiments using ground-based radio telescopes, through both single dish and Very Long Baseline Interferometry (VLBI) observations. The University of Tasmania (UTAS) is an important contributor to PRIDE and JUICE, though its continental-wide network of radio telescopes in Australia. Over 35 PRIDE observations of JUICE were conducted during the period 2023-24, which enabled detailed analysis of space weather activity in this period, as well as the Lunar-Earth flyby campaign in August 2024. In this paper, we describe PRIDE VLBI observations of JUICE, and the first successful results of PRIDE with the University of Tasmania infrastructure.

astro-ph.EP↗

arXiv2022

Detecting the oscillation and propagation of the nascent dynamic solar wind structure at 2.6 solar radii using VLBI radio telescopes

Probing the solar corona is crucial to study the coronal heating and solar wind acceleration. However, the transient and inhomogeneous solar wind flows carry large-amplitude inherent Alfven waves and turbulence, which make detection more difficult. We report the oscillation and propagation of the solar wind at 2.6 solar radii (Rs) by observation of China Tianwen and ESA Mars Express with radio telescopes. The observations were carried out on Oct.9 2021, when one coronal mass ejection (CME) passed across the ray paths of the telescope beams. We obtain the frequency fluctuations (FF) of the spacecraft signals from each individual telescope. Firstly, we visually identify the drift of the frequency spikes at a high spatial resolution of thousands of kilometers along the projected baselines. They are used as traces to estimate the solar wind velocity. Then we perform the cross-correlation analysis on the time series of FF from different telescopes. The velocity variations of solar wind structure along radial and tangential directions during the CME passage are obtained. The oscillation of tangential velocity confirms the detection of streamer wave. Moreover, at the tail of the CME, we detect the propagation of an accelerating fast field-aligned density structure indicating the presence of magnetohydrodynamic waves. This study confirm that the ground station-pairs are able to form particular spatial projection baselines with high resolution and sensitivity to study the detailed propagation of the nascent dynamic solar wind structure.

astro-ph.SR↗