Sensitivity analysis of polar orbiter motion to lunar viscoelastic tidal deformation

We investigate the impact of viscoelastic tidal deformation of the Moon on the motion of a polar orbiter. The dissipative effects in the Moon’s interior, i.e., tidal phase lags, are modeled as Fourier series sampled at given frequencies associated with linear combinations of Delaunay arguments, the fundamental parameters describing the lunar motion around the Earth and the Sun. We implement the tidal model to evaluate the temporal lunar gravity field and the induced perturbation on the orbiter. We validate the numerical scheme via a frequency analysis of the perturbed orbital motion. We show that, in the case of the Lunar Reconnaissance Orbiter at a low altitude of less than 200 km, the main lunar tides and hence the potential Love numbers around the monthly and some multiple frequencies are dynamically separable. The omission of those effects in practice introduces a position error at the level of a few decimeters within 10 days

Conceptual shape optimization of entry vehicles: applied to capsules and winged fuselage vehicles

This book covers the parameterization of entry capsules, including Apollo capsules and planetary probes, and winged entry vehicles such as the Space Shuttle and lifting bodies. The aerodynamic modelling is based on a variety of panel methods that take shadowing into account, and it has been validated with flight and wind tunnel data of Apollo and the Space Shuttle. The shape optimization is combined with constrained trajectory analysis, and the multi-objective approach provides the engineer with a Pareto front of optimal shapes. The method detailed in Conceptual Shape Optimization of Entry Vehicles is straightforward, and the output gives the engineer insight in the effect of shape variations on trajectory performance. All applied models and algorithms used are explained in detail, allowing for reconstructing the design tool to the researcher’s requirements. Conceptual Shape Optimization of Entry Vehicles will be of interest to both researchers and graduate students in the field of aerospace engineering, and to practitioners within the aerospace industry

Improvement of orbit determination using laser altimeter crossovers: JUICE mission case study

This work evaluates the added benefit of using laser altimeter measurements for orbit reconstruction. As a spacecraft orbits a celestial body, its altimetry swaths progressively cross previous swaths. These locations, known as crossover points, yield valuable information about the orbited body and the spacecraft trajectory. The mathematical expressions for the inclusion of crossover measurements into orbit determination algorithms are presented and evaluated. It is shown that a first-order approximation of these expressions is insufficient and a more detailed expression is developed. To evaluate the impact of altimetry crossover measurements on orbit determination, the planetary mission Jupiter Icy moons Explorer (JUICE) by the European Space Agency (ESA) is used as a case study by means of a covariance analysis. In this initial analysis, the assumption is made that all altimetry measurements are obtained with nadir pointing which limits the direct applicability of our method until pointing is accounted for

Survey of Capabilities and Applications of Accurate Clocks: Directions for Planetary Science

© 2017, Springer Science+Business Media B.V. For planetary science, accurate clocks are mainly used as part of an onboard radioscience transponder. In the case of two-way radio data, the dominating data type for planetary radioscience, an accurate spacecraft clock is not necessary since the measurements can be calibrated using high-precision clocks on Earth. In the case of one-way radio data, however, an accurate clock can make the precision of one-way radio data be comparable to the two-way data, and possibly better since only one leg of radio path would be affected by the media. This article addresses several ways to improve observations for planetary science, either by improving the onboard clock or by using further variants of the classical radioscience methods, e.g., Same Beam Interferometry (SBI). For a clock to be useful for planetary science, we conclude that it must have at least a short-time stability (<1,000s) better than 10 − 13 and its size be substantially miniaturized. A special case of using laser ranging to the Moon and the implication of having an accurate clock is shown as an example.status: publishe

The contribution of JUICE-PRIDE to Jovian system ephemerides

International audienceThe European Space Agency (ESA) Jupiter Icy Moons Explorer (JUICE) mission will perform detailed measurements of the properties of the Galilean moons, with a nominal mission duration of 4 years (2030-2033). Using both radio tracking data, and (Earth- and JUICE-based) optical astrometry, the dynamics of these moons can be derived to unprecedented accuracy. This will provide key input to the creation of ephemerides and the determination of physical properties of the Jovian system. We perform a general analysis of the Galilean moon dynamics that could be observable from JUICE data. Moreover, we specifically analyze the contribution to the ephemerides of VLBI data, obtained with the Planetary Radio Interferometry and Doppler Experiment (PRIDE) experiment.We perform a sensitivity analysis of the influence on the dynamics of the Galilean system for a wide array of undertainties in gravitational, tidal and rotational characteristics, and analyze the capabilities of the nominal (unperturbed) dynamical model to absorb the influence of these perturbations. Our results indicate that this nominal model can mostly absorb the influence of current uncertainties of the Galilean system's characteristics. A key exception is the dissipation in Io, which will likely be observable in the JUICE tracking data.The VLBI data from PRIDE will provide measurements of the motion of the moons perpendicular to their orbital planes. We perform a covariance analysis of the ephemeris generation for a broad range of mission and system characteristics, providing key input for the further development of the PRIDE observational planning and ground segment development.The results of the covariance analysis show that the VLBI data are crucially important for constraining the out-of-plane dynamics of Ganymede and Callisto. Also, the VLBI data make the ephemerides less dependent on the error in the orbit determination of the JUICE spacecraft itself. Furthermore, we find that optical astrometry data of Europa and Io using the JANUS instrument and/or the navigational camera will be crucial in stabilizing the solution of the normal equations

The contribution of JUICE-PRIDE to Jovian system ephemerides

International audienceThe European Space Agency (ESA) Jupiter Icy Moons Explorer (JUICE) mission will perform detailed measurements of the properties of the Galilean moons, with a nominal mission duration of 4 years (2030-2033). Using both radio tracking data, and (Earth- and JUICE-based) optical astrometry, the dynamics of these moons can be derived to unprecedented accuracy. This will provide key input to the creation of ephemerides and the determination of physical properties of the Jovian system. We perform a general analysis of the Galilean moon dynamics that could be observable from JUICE data. Moreover, we specifically analyze the contribution to the ephemerides of VLBI data, obtained with the Planetary Radio Interferometry and Doppler Experiment (PRIDE) experiment.We perform a sensitivity analysis of the influence on the dynamics of the Galilean system for a wide array of undertainties in gravitational, tidal and rotational characteristics, and analyze the capabilities of the nominal (unperturbed) dynamical model to absorb the influence of these perturbations. Our results indicate that this nominal model can mostly absorb the influence of current uncertainties of the Galilean system's characteristics. A key exception is the dissipation in Io, which will likely be observable in the JUICE tracking data.The VLBI data from PRIDE will provide measurements of the motion of the moons perpendicular to their orbital planes. We perform a covariance analysis of the ephemeris generation for a broad range of mission and system characteristics, providing key input for the further development of the PRIDE observational planning and ground segment development.The results of the covariance analysis show that the VLBI data are crucially important for constraining the out-of-plane dynamics of Ganymede and Callisto. Also, the VLBI data make the ephemerides less dependent on the error in the orbit determination of the JUICE spacecraft itself. Furthermore, we find that optical astrometry data of Europa and Io using the JANUS instrument and/or the navigational camera will be crucial in stabilizing the solution of the normal equations

Contribution of simultaneous PRIDE observations of JUICE and Clipper spacecraft to the Galilean satellites' ephemerides

International audienc