Rosetta Radio Science Investigations (RSI)

Pätzold, M.; Häusler, B.; Aksnes, K.; Anderson, J. D.; Asmar, S. W.; Barriot, J. P.; Bird, M. K.; Boehnhardt, H.; Eidel, W.; Grün, E.; Ip, W.-H.; Marouf, E. A.; Morley, T. A.; Neubauer, F. M.; Rickman, H.; Thomas, Nicolas; Tsurutani, B. T.; Wallis, M. K.; Wickramasinghe, N. C.; Mysen, E.; Olson, Oystein; Remus, S.; Tellmann, S.; Andert, T.; Carone, L.; Fels, Markus; Stanzel, C.; Audenrieth-Kersten, Iris; Gahr, Alexander; Muller, Anna; Stupar, D.; Walter, Christina

doi:10.1007/s11214-006-9117-7

Cited by 40 publications

(25 citation statements)

References 53 publications

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“…It is anticipated, however, that this will be possible with the Rosetta spacecraft orbiting 67P/Churyumov-Gerasimenko (Pätzold et al 2007). It will be a good test for our model.…”

Section: Discussionmentioning

confidence: 99%

CONGO, model of cometary non-gravitational forces combining astrometric and production rate data

Maquet

Colas

Jordá

et al. 2012

A&A

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The gravitational orbit of a comet is affected by the sublimation of water molecules by the nucleus when the comet approaches perihelion. This outgassing triggers a non-gravitational force (NGF) that significantly modifies the orbit of the comet. Up to now, modelling of this effect is mostly based on an empirical model defined in the early 70s that uses a simplified outgassing model. Attempts have been made to use advanced anisotropic thermal models both to calculate the NGF taking several observational constraints into account and to retrieve the nucleus's mass and density, but (i) this approach is restricted to a handful of cometary nuclei that are sufficiently well known to allow this type of modelling, and (ii) the authors usually do not fit the astrometric measurements directly but rather non-gravitational parameters calculated with the above-mentioned empirical model. We present a new model for non-gravitational forces with the aim of revisiting the problem of NGF calculation and nucleus density determination. Our model is closer to the nucleus outgassing physics with only a few free parameters. The amplitude of the perturbation depends on several parameters describing the comet activity that can be constrained by visible, infrared, and radio observations of the coma and the nucleus of the comet. It also depends on the nucleus mass, which can in turn be determined by modelling the effect of the NGF on the orbit of a comet. The method is based on the decomposition of the surface of the nucleus in several elements located at different latitudes. The contribution of each surface element to the overall NGF is fitted from the astrometric measurements, together with the density of the nucleus. This method is the only one available so far to estimate the density of cometary nuclei from ground-based observations. This method is tested on the well-known comet 19P/Borrelly. The density found for these comet is between 150 and 600 kg m −3 .

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“…It is anticipated, however, that this will be possible with the Rosetta spacecraft orbiting 67P/Churyumov-Gerasimenko (Pätzold et al 2007). It will be a good test for our model.…”

Section: Discussionmentioning

confidence: 99%

CONGO, model of cometary non-gravitational forces combining astrometric and production rate data

Maquet

Colas

Jordá

et al. 2012

A&A

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“…In this case we need to know V 2 for each different chemical species to calculate this component of the force. In navigation and radio science, where scientific quantities are found by inverting radiometric data from the spacecraft (Pätzold et al 2007), only the properties of the chemical species which contributes the most can be found. That is, if we can find a proper parametrization of V 2 , we do not necessarily have to operate with one such set of parameters for each chemical species.…”

Section: Total Force From Both Sides Of a Flat Platementioning

confidence: 99%

“…12 where isocontours of Δχ ≡ χ max − χ min are mapped over a rotation period. These temporal variations with rotation are particularly important when the second degree and order gravity field of the nucleus are to be extrapolated from Doppler data (Pätzold et al 2007), since both effects induce variations in the Doppler data with roughly the same frequencies. Notice the small amplitudes in the night-side of the coma in Fig.…”

Section: Variabilitymentioning

confidence: 99%

“…As for Rosetta, one essential data type for the radio science objectives, like the determination of the comet nucleus' gravity field, are Doppler data with an observation noise of 0.01 mm s −1 for long integration times (Pätzold et al 2007). Below we shall use the cometocentric velocity componentŻ of the spacecraft in the direction of the Sun as the Doppler observable, an acceptable approximation since the cometocentric direction of the Earth approximately coincides with that of the Sun at the early stages of the Rosetta mission (Mysen & Aksnes 2008).…”

Section: Mean Field Modelmentioning

confidence: 99%

“…A stated goal of the Rosetta Radio Science Investigations is the determination of the nucleus' gravity field from Doppler data (Pätzold et al 2007). In other words, the gravity field of 67P can be determined by the study of how the comet's gravity alters the line-of-sight velocity of Rosetta in its orbit around the comet.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

An analysis of outgassing pressure forces on the Rosetta orbiter using realistic 3D+t coma simulations

Mysen¹,

Родионов

Crifo

2010

A&A

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A model for the interaction between a multicomponent Maxwellian atmosphere and a spacecraft is described. Multidimensional, time-dependent gasdynamical simulations of the gas coma around the recently reconstructed aspherical rotating nucleus of comet 67P/C-G is used to analyze the outgassing pressure forces on the ESA spacecraft Rosetta. The forces were in general found to be directed significantly away from the cometocentric position vector of the spacecraft. It was also found that in a maximum outgassing scenario at comet rendezvous, the outgassing pressure force exceeds the gravitational attraction from the nucleus in the cometocentric direction of the Sun. Furthermore, the highly non-spherical pressure field was found to undergo very large changes as the nucleus rotated. Still, it was possible to represent the mean pressure field experienced by Rosetta by a fairly simple model, which can be used for the determination of the comet mass and the so-called oblateness coefficient c 20 from the spacecraft Doppler signal. The oblateness coefficient represents a type of asphericity of the gravity field. The determination of the so-called triaxiality coefficient of the gravity field c 22 may require using the true pressure field instead of the mean pressure field.

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Comment on the paper “Mars Express radio occultation data: A novel analysis approach” by Grandin et al. (2014)

et al. 2016

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In their recent paper, Grandin et al. (2014) claim to have developed a novel approach, principally a ray tracing method, to analyze radio sounding data from occulted spacecraft signals by planetary atmospheres without the usual assumptions of the radio occultation inversion method of a stratified, layered, symmetric atmosphere. They apply their “new approach” to observations of the Mars Express Radio Science (MaRS) experiment and compare their resulting temperature, neutral number density, and electron density profiles with those from MaRS, claiming that there is good agreement with the observations. The fact is, however, that there are serious disagreements in the most important altitude ranges. Their temperature profile shows a 30 K shift or a 300σ (1σ standard deviation = 0.1 K for the MaRS profile near the surface) difference toward warmer temperatures at the surface when compared with MaRS, while the MaRS profile is in best agreement with the profile from the Mars Climate Data Base V5.0 (MCD V5.0). Their full temperature profile from the surface to 250 km altitude deviates significantly from the MCD V5.0 profile. Their ionospheric electron density profile is considerably different from that derived from the MaRs observations. Although Grandin et al. (2014) claim to derive the neutral number density and temperature profiles above 200 km, including the asymptotic exosphere temperature, it is simply not possible to derive this information from what is essentially noise.

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Rosetta Radio Science Investigations (RSI)

Cited by 40 publications

References 53 publications

CONGO, model of cometary non-gravitational forces combining astrometric and production rate data

CONGO, model of cometary non-gravitational forces combining astrometric and production rate data

An analysis of outgassing pressure forces on the Rosetta orbiter using realistic 3D+t coma simulations

Comment on the paper “Mars Express radio occultation data: A novel analysis approach” by Grandin et al. (2014)

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