Determination of uncertainty profiles in neutral atmospheric properties measured by radio occultation experiments

Bourgoin, Adrien; Gramigna, Edoardo; Zannoni, Marco; Casajus, Luis Gomez; Tortora, Paolo

doi:10.1016/j.asr.2022.07.015

Cited by 3 publications

(5 citation statements)

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“…With this procedure we obtain P ( r 0 ) ≃ 3 Pa and T ( r 0 ) ≃ 165 K. The whole pressure and temperature profiles are shown in Figure 5 along with error bars that represent an estimate of the uncertainties in the pressure and temperature values due to thermal noise, obtained with the approximate expressions introduced by Bourgoin et al. (2022). Figure 5 depicts that the temperature and pressure values are consistent with those expected by the numerical simulation of Mars' atmosphere presented in the Mars Climate Database; see Forget et al.…”

Section: Test Casesmentioning

confidence: 82%

“…The error bars show an estimate of the uncertainty due to thermal noise; see Bourgoin et al. (2022).…”

Section: Test Casesmentioning

confidence: 99%

“…Profiles for Mars' atmospheric properties retrieved during MAVEN two-way occultation: comparison between the temperature and pressure profiles obtained using the ray-tracing method and those retrieved from the Mars Climate Database. The error bars show an estimate of the uncertainty due to thermal noise; seeBourgoin et al (2022).…”

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confidence: 99%

“…All in all, refraction thus generates both an excess path delay and a geometrical delay with respect to a signal that would have been transmitted in a neat vacuum (Bourgoin et al, 2021). The variations of these atmospheric delays with respect to the positions of the emitter and receiver eventually describe how refraction may disrupt the frequency of the electromagnetic signal (see e.g., Bourgoin, 2020;Bourgoin et al, 2021Bourgoin et al, , 2022Synge, 1960). These are the mechanisms that one should properly account for in order to provide an accurate processing of radio occultation data.…”

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confidence: 99%

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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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Section: Test Casesmentioning

confidence: 82%

“…The error bars show an estimate of the uncertainty due to thermal noise; see Bourgoin et al. (2022).…”

Section: Test Casesmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Radio Occultation Data Analysis With Analytical Ray‐Tracing

Caruso,

Bourgoin,

Togni

et al. 2023

Radio Science

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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%

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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Characterization of the Surfaces and Near-Surface Atmospheres of Ganymede, Europa and Callisto by JUICE

Tosi,

Roatsch,

Galli

et al. 2024

Space Sci Rev

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We present the state of the art on the study of surfaces and tenuous atmospheres of the icy Galilean satellites Ganymede, Europa and Callisto, from past and ongoing space exploration conducted with several spacecraft to recent telescopic observations, and we show how the ESA JUICE mission plans to explore these surfaces and atmospheres in detail with its scientific payload. The surface geology of the moons is the main evidence of their evolution and reflects the internal heating provided by tidal interactions. Surface composition is the result of endogenous and exogenous processes, with the former providing valuable information about the potential composition of shallow subsurface liquid pockets, possibly connected to deeper oceans. Finally, the icy Galilean moons have tenuous atmospheres that arise from charged particle sputtering affecting their surfaces. In the case of Europa, plumes of water vapour have also been reported, whose phenomenology at present is poorly understood and requires future close exploration. In the three main sections of the article, we discuss these topics, highlighting the key scientific objectives and investigations to be achieved by JUICE. Based on a recent predicted trajectory, we also show potential coverage maps and other examples of reference measurements. The scientific discussion and observation planning presented here are the outcome of the JUICE Working Group 2 (WG2): “Surfaces and Near-surface Exospheres of the Satellites, dust and rings”.

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Determination of uncertainty profiles in neutral atmospheric properties measured by radio occultation experiments

Cited by 3 publications

References 40 publications

Radio Occultation Data Analysis With Analytical Ray‐Tracing

Radio Occultation Data Analysis With Analytical Ray‐Tracing

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

Characterization of the Surfaces and Near-Surface Atmospheres of Ganymede, Europa and Callisto by JUICE

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