Analysis of NASA’s DSN Venus Express radio occultation data for year 2014

Gramigna, Edoardo; Parisi, Marzia; Buccino, Dustin; Casajus, Luis Gomez; Zannoni, Marco; Bourgoin, Adrien; Tortora, Paolo; Oudrhiri, Kamal

doi:10.1016/j.asr.2022.10.070

Cited by 5 publications

(6 citation statements)

References 51 publications

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“…The approach yields a constant value of the standard deviation with altitude, as presented by Dalba and Withers (2019) for determining the accuracy on Titan's ionospheric profiles. A different approach involves the usage of Monte Carlo analyses, used to calculate the formal 1 σ uncertainties (darker blue shaded areas in Figures 3a and 3b) as a function of altitude (Bourgoin et al., 2022; Gramigna et al., 2023). Gaussian random noise time‐series, with standard deviation matching the observed noise levels outside Europa's ionosphere, were added to the original differential frequency residuals.…”

Section: Resultsmentioning

confidence: 99%

“…Furthermore, an additional calibration step on the Doppler data was performed. A linear bias was removed from the residuals, as is often done to compensate for interplanetary plasma effects (Gramigna et al., 2023; Kliore et al., 1997). The bias was calculated separately for ingress and egress, using data points corresponding to ray path altitudes above 1,500 km (called the baseline, Figures 2e and 2f), where it is assumed that the spacecraft's signals were propagating well outside Europa's ionosphere (Text S1 in Supporting Information ).…”

Section: Analysis Methods and Data Setmentioning

confidence: 99%

Section: Analysis Methods and Data Setmentioning

confidence: 99%

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Radio Occultation Measurements of Europa's Ionosphere From Juno's Close Flyby

Parisi,

Caruso,

Buccino

et al. 2023

Geophysical Research Letters

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On 29 September 2022 the Juno spacecraft flew within 354 km of Europa's surface while several instruments probed the moon's surroundings. During the close flyby, radio occultations were performed by collecting single‐frequency Doppler measurements. These investigations are essential to the study of Europa's ionosphere and represent the first repeat sampling of any set of conditions since the Galileo era. Ingress measurements resulted in a marginal detection with a peak ionospheric density of 4,000 ± 3,700 cm−3 (3σ) at 22 km altitude. A more significant detection emerged on egress, with a peak density of 6,000 ± 3,000 cm−3 (3σ) at 320 km altitude. Comparison with Galileo measurements reveals a consistent picture of Europa's ionosphere, and confirms its dependence on illumination conditions and position within Jupiter's magnetosphere. However, the overall lower densities measured by Juno suggest a dependence on time of observation, with implications for the structure of the neutral atmosphere.

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Section: Resultsmentioning

confidence: 99%

Section: Analysis Methods and Data Setmentioning

confidence: 99%

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Radio Occultation Measurements of Europa's Ionosphere From Juno's Close Flyby

Parisi,

Caruso,

Buccino

et al. 2023

Geophysical Research Letters

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“…Also, if the occulting body has a solid surface, the m th shell extends down to the planet radius R p , with R p = r m +1 . In the case of a planet without a solid surface or for Venus, in which critical refraction prevents the ray from penetrating inside the lower atmosphere below 40 km (Gramigna et al., 2023), it may be possible to guess an arbitrary minimum radius r m +1 below which we know the ray cannot penetrate or simply putting r m +1 = 0. In Figure 2 to the left, we depicted a light ray trajectory across a layered atmosphere.…”

Section: Mathematical Modeling Of a Radio Signal Pathmentioning

confidence: 99%

“…One of the most widely used methods to process one‐way radio occultation data for spherically symmetric atmospheres is based on Abel transform algorithms (Fjeldbo et al., 1971; Phinney & Anderson, 1968). This method was applied to the atmospheres of many planets and moons, such as Mars (Pätzold et al., 2016; Petricca et al., 2021; Withers & Moore, 2020; Withers et al., 2014), Venus (Ando et al., 2020; Bocanegra‐Bahamón et al., 2019; Fjeldbo et al., 1971; Gramigna et al., 2023; Häusler et al., 2006), and Titan (Schinder et al., 2011b, 2020). It directly returns the refractivity profile from the bending angle and the impact parameter of the radio signal.…”

Section: Introductionmentioning

confidence: 99%

Radio Occultation Data Analysis With Analytical Ray‐Tracing

Caruso,

Bourgoin,

Togni

et al. 2023

Radio Science

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Radio occultation experiments are a sensing technique dedicated to the remote sounding of planetary atmospheres. The technique exploits the frequency shift of a radio signal due to refraction in a planetary atmosphere. The aim is to infer the physical properties of the neutral atmosphere (e.g., pressure and temperature) and ionosphere (e.g., the electron number density). For one‐way occultations, the data processing usually relies on Abel transform algorithms when the atmosphere is spherically symmetric. For two‐way occultations, such techniques require the introduction of approximate relationships for the bending experienced by the signal to be obtained. In this context, we introduce a new method to process two‐way occultations data by spherically symmetric atmospheres using a ray‐tracing approach. However, the numerical integration of the geometrical optics equation through the atmosphere requires a significant computational time due to initial pointing issues. For this reason, our novel algorithm exploits a closed‐form solution to the equations of geometrical optics (Bourgoin et al., A&A, 624, A41, 2019) applied to a spherically symmetric atmosphere. Within this approach, the bending is directly provided by the analytical solution and no numerical integration is required. In addition, we develop a procedure enabling us to disentangle the contributions from dispersive and neutral media in the frequency shift. This procedure is validated by comparing our vertical profiles to those obtained using Abel inversion or numerical ray‐tracing for Mars and Titan occultation experiments. We show that our algorithm provides similar results to purely numerical ray‐tracing algorithms while significantly decreasing the computational time.

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