In its tour of the Saturnian system, begun on July 1st, 2004, the Cassini spacecraft had many clo... more In its tour of the Saturnian system, begun on July 1st, 2004, the Cassini spacecraft had many close flybys of Saturn's main satellites. However, due to impossibility to carry out simultaneously remote sensing observations and microwave tracking from ground, only a small fraction of those flybys could be exploited for gravity measurements. So far, the quadrupole field has been mapped only for Titan, Rhea and Enceladus, while for Hyperion and Iapetus the mass was the only accessible parameter. For Titan and Enceladus, the only satellites targeted more than once for gravity observations, also a rough geoid to degree and order 3 has been determined. Satellite gravity investigations rely upon accurate measurements of the spacecraft range rate, enabled by coherent, two-way radio links at X and Ka band (8.4 and 32.5 GHz). The use of hydrogen masers frequency standards at the ground station and the consid-erable suppression of plasma noise at X and Ka band frequen-cies provide range rat...
On 27 August 2016, the Juno spacecraft acquired science observations of Jupiter, passing less tha... more On 27 August 2016, the Juno spacecraft acquired science observations of Jupiter, passing less than 5000 kilometers above the equatorial cloud tops. Images of Jupiter's poles show a chaotic scene, unlike Saturn's poles. Microwave sounding reveals weather features at pressures deeper than 100 bars, dominated by an ammonia-rich, narrow low-latitude plume resembling a deeper, wider version of Earth's Hadley cell. Near-infrared mapping reveals the relative humidity within prominent downwelling regions. Juno's measured gravity field differs substantially from the last available estimate and is one order of magnitude more precise. This has implications for the distribution of heavy elements in the interior, including the existence and mass of Jupiter's core. The observed magnetic field exhibits smaller spatial variations than expected, indicative of a rich harmonic content.
Deep space exploration missions are aimed at acquiring information about the solar system and a s... more Deep space exploration missions are aimed at acquiring information about the solar system and a significant communication capacity has to be planned to transfer data for such very large distances [1]. Terrestrial atmospheric impairments on the space-to-Earth propagating signal are the major responsible for the signal degradation thus reducing the channel temporal availability [2]-[4]. In this work weather forecast models, coupled with microphysically-oriented radio-propagation models, are described in order to evaluate atmospheric effects at Ka-band. Estimation data return techniques are summarized and numerical results in a simulated operational scenario are illustrated in terms of received data volume using the BepiColombo mission as a baseline example.
The proposed mission "Space Atomic Gravity Explorer" (SAGE) has the scientific objective to inves... more The proposed mission "Space Atomic Gravity Explorer" (SAGE) has the scientific objective to investigate gravitational waves, dark matter, and other fundamental aspects of gravity as well as the connection between gravitational physics and quantum physics using new quantum sensors, namely, optical atomic clocks and atom interferometers based on ultracold strontium atoms.
upcoming high precision measurements of the Juno flybys around Jupiter, have the potential of imp... more upcoming high precision measurements of the Juno flybys around Jupiter, have the potential of improving the estimation of Jupiter's gravity field. The analysis of the Juno Doppler data will provide a very accurate reconstruction of spacial gravity variations, but these measurements will be over a limited latitudinal and longitudinal range. In order to deduce the full gravity field of Jupiter, additional information needs to be incorporated into the analysis, especially with regards to the Jovian wind structure and its depth at high latitudes. In this work we propose a new iterative method for the estimation of the Jupiter gravity field, using the Juno expected measurements, a trajectory estimation model, and an adjoint based inverse thermal wind model. The results show that using this method the gravitational field isfitted better to the 'observed' one, mainly due to the fact that the thermal wind model is taking into consideration the wind structure and depth. Thus, it is suggested that the method presented here has the potential of improving the accuracy of the gravity field calculated from the expected Juno flyby observations. Introduction perturbations to the gravity fields of Jupiter can result from mass anomalies due to two sources—the rapid rotation of these planets, which distorts the planets into a nonspherical (oblate) shape, and density perturbations, which result from fast atmospheric winds organized on both planets into a broad zone of westward flow near the equator and eastward flow at high latitudes. The gravity field can be decomposed into spherical gravity harmonics, (J n ), which are defined as a weighted integral over the planets' density distribution:
In 1992 and 1993 the interplanetary probe ULYSSES (ESA) has been tracked in Doppler mode using se... more In 1992 and 1993 the interplanetary probe ULYSSES (ESA) has been tracked in Doppler mode using several ground antennas with the goal to detect low frequency gravitational waves. This experiment is part of a long terms program undertaken by NASA and ESA for the detection of gravitational waves in space. The authors summarize the results of a search for quasi-periodic
The first opposition test of Doppler tracking the Ulysses spacecraft from the Medicina VLBI (Very... more The first opposition test of Doppler tracking the Ulysses spacecraft from the Medicina VLBI (Very Long Base Interferometry) station (Italy) proved its capability to perform a systematic search for gravitational waves. In house and JPL (Jet Propulsion Laboratory) data analysis showed that the target Allan variance of 3 x 10(exp -14) at 1000 s, planned for the DSN antennas was also achieved from the station. The main observation campaign during the second opposition phase will last for thirty continuous nights--from mid Feb. to mid Mar. 1992. The main hardware and software features developed for this application, together with some results of the first opposition test, are described.
Radio remote sensing of the heliosphere using spacecraft radio signals has been used to study the... more Radio remote sensing of the heliosphere using spacecraft radio signals has been used to study the near-sun plasma in and out of the ecliptic, close to the sun, and on spatial and temporal scales not accessible with other techniques. Studies of space-time variations in the inner solar wind are particularly timely because of the desire to understand and predict space weather, which can disturb satellites and systems at 1AU and affect human space exploration. Here we demonstrate proof-of-concept of a new radio science application for spacecraft radio science links. The differing transfer functions of plasma irregularities to spacecraft radio up-and downlinks can be exploited to localize plasma scattering along the line of sight. We demonstrate the utility of this idea using Cassini radio data taken in 2001-2002. Under favorable circumstances we demonstrate how this technique, unlike other remote sensing methods, can determine center-ofscattering position to within a few thousandths of an AU and thickness of scattering region to less than about 0.02 AU. This method, applied to large data sets and used in conjunction with other solar remote sensing data such as white light data, has space weather application in studies of inhomogeneity and nonstationarity in the near-sun solar wind. An edited version of this paper was published by AGU with copyright (2009) American Geophysical Union.
The outer planets of our solar system Jupiter, Saturn, Uranus, and Neptune are fascinating object... more The outer planets of our solar system Jupiter, Saturn, Uranus, and Neptune are fascinating objects on their own. Their intrinsic magnetic fields form magnetic environments (so called magnetospheres) in which charged and neutral particles and dust are produced, lost or being transported through the system. These magnetic environments of the gas giants can be envisaged as huge plasma laboratories in space in which electromagnetic waves, current systems, particle transport mechanisms, acceleration processes and other phenomena act and interact with the large number of moons in orbit around those massive planets. In general it is necessary to describe and study the global environments (magnetospheres) of the gas giants, its global configuration with its large-scale transport processes; and, in combination, to study the local environments of the moons as well, e.g. the interac
In response to ESA's Call for proposals of 5 March 2007 of the COSMIC VISION 2015-2025 plan of th... more In response to ESA's Call for proposals of 5 March 2007 of the COSMIC VISION 2015-2025 plan of the ESA science programme, we propose a M-class satellite mission to test of the Equivalence Principle in the quantum domain by investigating the extended free fall of matter waves instead of macroscopic bodies as in the case of GAUGE, MICROSCOPE or STEP. The satellite, called Matter Wave Explorer of Gravity, will carry an experiment to test gravity, namely the measurement of the equal rate of free fall with various isotopes of distinct atomic species with precision cold atom interferometry in the vicinity of the earth. This will allow for a first quantum test the Equivalence Principle with spin polarised particles and with pure fermionic and bosonic atomic ensembles. Due to the space conditions, the free fall of Rubidium and Potassium isotopes will be compared with a maximum accelerational sensitivity of 5•10 −16 m/s 2 corresponding to an accuracy of the test of the Equivalence Principle of 1 part in 10 16. Besides the primary scientific goal, the quantum test of the Equivalence Principle, the mission can be extended to provide additional information about the gravitational field of the earth or for testing theories of fundamental processes of decoherence which are investigated by various theory groups in the context of quantum gravity phenomenology. In
In 2002 a measurement of the effect of solar gravity upon the phase of coherent microwave beams p... more In 2002 a measurement of the effect of solar gravity upon the phase of coherent microwave beams passing near the Sun has been carried out with the Cassini mission, allowing a very accurate measurement of the PPN parameter γ. The data have been analyzed with NASA's Orbit Determination Program (ODP) in the Barycentric Celestial Reference System, in which the Sun moves around the centre of mass of the solar system with a velocity v ⊙ of about 10 m/sec; the question arises, what correction this implies for the predicted phase shift. After a review of the way the ODP works, we set the problem in the framework of Lorentz (and Galilean) transformations and evaluate the correction; it is several orders of magnitude below our experimental accuracy. We also discuss a recent paper [10], which claims wrong and much larger corrections, and clarify the reasons for the discrepancy.
Understanding the processes that led Venus to its current state and will drive its future evoluti... more Understanding the processes that led Venus to its current state and will drive its future evolution is a major objective of the next generation of orbiters. In this work we analyze the retrieval of the spin vector, the tidal response, and the moment of inertia of Venus with VERITAS, a NASA Discovery-class mission. By simulating a systematic joint analysis of Doppler tracking data and tie points provided by the onboard synthetic aperture radar, we show that VERITAS will provide accuracies (3σ) in the estimates of the tidal Love number k 2 to 4.6 × 10 −4 , its tidal phase lag to 0°. 05, and the moment of inertia factor to 9.8 × 10 −4 (0.3% of the expected value). Applying these results to recent models of the Venus interior, we show that VERITAS will provide much-improved constraints on the interior structure of the planet.
On October and December 2004 the Cassini spacecraft performed two flybys of Saturn\u2019s moon Ia... more On October and December 2004 the Cassini spacecraft performed two flybys of Saturn\u2019s moon Iapetus. Although the closest approach distance was large and the encounters barely deserve the name of flybys, they provided the first opportunity for an accurate determination of the satellite\u2019s mass and density. The good quality of the Cassini X-band Doppler data allowed a substantial reduction of the experimental uncertainty obtained with past measurements. The orbital fit of the spacecraft trajectory was carried out over arcs of 15 days about the closest approach and used a limited set of solve-for parameters. Our best estimate of the satellite\u2019s gravitational parameter results from the first and more distant flyby. The second flyby, occurring at a much closer distance, gave a smaller formal error and a rather consistent estimate, but the orbital solution was much more affected by the uncertainties in Iapetus ephemerides and likely to be biased
Microwave tracking, usually performed by on ground processing of the signals coming from a spacec... more Microwave tracking, usually performed by on ground processing of the signals coming from a spacecraft, represents a crucial aspect in every deep-space mission. Various noise sources, including receiver noise, affect these signals, limiting the accuracy of the radiometric measurements obtained from the radio link. There are several methods used for spacecraft tracking, including the Delta-Differential One-Way Ranging ( Δ DOR) technique. In the past years, European Space Agency (ESA) missions relied on a narrowband Δ DOR system for navigation in the cruise phase. To limit the adverse effect of nonlinearities in the receiving chain, an innovative wideband approach to Δ DOR measurements has recently been proposed. This work presents the hardware implementation of a new version of the ESA X/Ka Deep Space Transponder based on the new tracking technique named Wideband Δ DOR (W- Δ DOR). The architecture of the new transponder guarantees backward compatibility with narrowband Δ DOR.
In its tour of the Saturnian system, begun on July 1st, 2004, the Cassini spacecraft had many clo... more In its tour of the Saturnian system, begun on July 1st, 2004, the Cassini spacecraft had many close flybys of Saturn's main satellites. However, due to impossibility to carry out simultaneously remote sensing observations and microwave tracking from ground, only a small fraction of those flybys could be exploited for gravity measurements. So far, the quadrupole field has been mapped only for Titan, Rhea and Enceladus, while for Hyperion and Iapetus the mass was the only accessible parameter. For Titan and Enceladus, the only satellites targeted more than once for gravity observations, also a rough geoid to degree and order 3 has been determined. Satellite gravity investigations rely upon accurate measurements of the spacecraft range rate, enabled by coherent, two-way radio links at X and Ka band (8.4 and 32.5 GHz). The use of hydrogen masers frequency standards at the ground station and the consid-erable suppression of plasma noise at X and Ka band frequen-cies provide range rat...
On 27 August 2016, the Juno spacecraft acquired science observations of Jupiter, passing less tha... more On 27 August 2016, the Juno spacecraft acquired science observations of Jupiter, passing less than 5000 kilometers above the equatorial cloud tops. Images of Jupiter's poles show a chaotic scene, unlike Saturn's poles. Microwave sounding reveals weather features at pressures deeper than 100 bars, dominated by an ammonia-rich, narrow low-latitude plume resembling a deeper, wider version of Earth's Hadley cell. Near-infrared mapping reveals the relative humidity within prominent downwelling regions. Juno's measured gravity field differs substantially from the last available estimate and is one order of magnitude more precise. This has implications for the distribution of heavy elements in the interior, including the existence and mass of Jupiter's core. The observed magnetic field exhibits smaller spatial variations than expected, indicative of a rich harmonic content.
Deep space exploration missions are aimed at acquiring information about the solar system and a s... more Deep space exploration missions are aimed at acquiring information about the solar system and a significant communication capacity has to be planned to transfer data for such very large distances [1]. Terrestrial atmospheric impairments on the space-to-Earth propagating signal are the major responsible for the signal degradation thus reducing the channel temporal availability [2]-[4]. In this work weather forecast models, coupled with microphysically-oriented radio-propagation models, are described in order to evaluate atmospheric effects at Ka-band. Estimation data return techniques are summarized and numerical results in a simulated operational scenario are illustrated in terms of received data volume using the BepiColombo mission as a baseline example.
The proposed mission "Space Atomic Gravity Explorer" (SAGE) has the scientific objective to inves... more The proposed mission "Space Atomic Gravity Explorer" (SAGE) has the scientific objective to investigate gravitational waves, dark matter, and other fundamental aspects of gravity as well as the connection between gravitational physics and quantum physics using new quantum sensors, namely, optical atomic clocks and atom interferometers based on ultracold strontium atoms.
upcoming high precision measurements of the Juno flybys around Jupiter, have the potential of imp... more upcoming high precision measurements of the Juno flybys around Jupiter, have the potential of improving the estimation of Jupiter's gravity field. The analysis of the Juno Doppler data will provide a very accurate reconstruction of spacial gravity variations, but these measurements will be over a limited latitudinal and longitudinal range. In order to deduce the full gravity field of Jupiter, additional information needs to be incorporated into the analysis, especially with regards to the Jovian wind structure and its depth at high latitudes. In this work we propose a new iterative method for the estimation of the Jupiter gravity field, using the Juno expected measurements, a trajectory estimation model, and an adjoint based inverse thermal wind model. The results show that using this method the gravitational field isfitted better to the 'observed' one, mainly due to the fact that the thermal wind model is taking into consideration the wind structure and depth. Thus, it is suggested that the method presented here has the potential of improving the accuracy of the gravity field calculated from the expected Juno flyby observations. Introduction perturbations to the gravity fields of Jupiter can result from mass anomalies due to two sources—the rapid rotation of these planets, which distorts the planets into a nonspherical (oblate) shape, and density perturbations, which result from fast atmospheric winds organized on both planets into a broad zone of westward flow near the equator and eastward flow at high latitudes. The gravity field can be decomposed into spherical gravity harmonics, (J n ), which are defined as a weighted integral over the planets' density distribution:
In 1992 and 1993 the interplanetary probe ULYSSES (ESA) has been tracked in Doppler mode using se... more In 1992 and 1993 the interplanetary probe ULYSSES (ESA) has been tracked in Doppler mode using several ground antennas with the goal to detect low frequency gravitational waves. This experiment is part of a long terms program undertaken by NASA and ESA for the detection of gravitational waves in space. The authors summarize the results of a search for quasi-periodic
The first opposition test of Doppler tracking the Ulysses spacecraft from the Medicina VLBI (Very... more The first opposition test of Doppler tracking the Ulysses spacecraft from the Medicina VLBI (Very Long Base Interferometry) station (Italy) proved its capability to perform a systematic search for gravitational waves. In house and JPL (Jet Propulsion Laboratory) data analysis showed that the target Allan variance of 3 x 10(exp -14) at 1000 s, planned for the DSN antennas was also achieved from the station. The main observation campaign during the second opposition phase will last for thirty continuous nights--from mid Feb. to mid Mar. 1992. The main hardware and software features developed for this application, together with some results of the first opposition test, are described.
Radio remote sensing of the heliosphere using spacecraft radio signals has been used to study the... more Radio remote sensing of the heliosphere using spacecraft radio signals has been used to study the near-sun plasma in and out of the ecliptic, close to the sun, and on spatial and temporal scales not accessible with other techniques. Studies of space-time variations in the inner solar wind are particularly timely because of the desire to understand and predict space weather, which can disturb satellites and systems at 1AU and affect human space exploration. Here we demonstrate proof-of-concept of a new radio science application for spacecraft radio science links. The differing transfer functions of plasma irregularities to spacecraft radio up-and downlinks can be exploited to localize plasma scattering along the line of sight. We demonstrate the utility of this idea using Cassini radio data taken in 2001-2002. Under favorable circumstances we demonstrate how this technique, unlike other remote sensing methods, can determine center-ofscattering position to within a few thousandths of an AU and thickness of scattering region to less than about 0.02 AU. This method, applied to large data sets and used in conjunction with other solar remote sensing data such as white light data, has space weather application in studies of inhomogeneity and nonstationarity in the near-sun solar wind. An edited version of this paper was published by AGU with copyright (2009) American Geophysical Union.
The outer planets of our solar system Jupiter, Saturn, Uranus, and Neptune are fascinating object... more The outer planets of our solar system Jupiter, Saturn, Uranus, and Neptune are fascinating objects on their own. Their intrinsic magnetic fields form magnetic environments (so called magnetospheres) in which charged and neutral particles and dust are produced, lost or being transported through the system. These magnetic environments of the gas giants can be envisaged as huge plasma laboratories in space in which electromagnetic waves, current systems, particle transport mechanisms, acceleration processes and other phenomena act and interact with the large number of moons in orbit around those massive planets. In general it is necessary to describe and study the global environments (magnetospheres) of the gas giants, its global configuration with its large-scale transport processes; and, in combination, to study the local environments of the moons as well, e.g. the interac
In response to ESA's Call for proposals of 5 March 2007 of the COSMIC VISION 2015-2025 plan of th... more In response to ESA's Call for proposals of 5 March 2007 of the COSMIC VISION 2015-2025 plan of the ESA science programme, we propose a M-class satellite mission to test of the Equivalence Principle in the quantum domain by investigating the extended free fall of matter waves instead of macroscopic bodies as in the case of GAUGE, MICROSCOPE or STEP. The satellite, called Matter Wave Explorer of Gravity, will carry an experiment to test gravity, namely the measurement of the equal rate of free fall with various isotopes of distinct atomic species with precision cold atom interferometry in the vicinity of the earth. This will allow for a first quantum test the Equivalence Principle with spin polarised particles and with pure fermionic and bosonic atomic ensembles. Due to the space conditions, the free fall of Rubidium and Potassium isotopes will be compared with a maximum accelerational sensitivity of 5•10 −16 m/s 2 corresponding to an accuracy of the test of the Equivalence Principle of 1 part in 10 16. Besides the primary scientific goal, the quantum test of the Equivalence Principle, the mission can be extended to provide additional information about the gravitational field of the earth or for testing theories of fundamental processes of decoherence which are investigated by various theory groups in the context of quantum gravity phenomenology. In
In 2002 a measurement of the effect of solar gravity upon the phase of coherent microwave beams p... more In 2002 a measurement of the effect of solar gravity upon the phase of coherent microwave beams passing near the Sun has been carried out with the Cassini mission, allowing a very accurate measurement of the PPN parameter γ. The data have been analyzed with NASA's Orbit Determination Program (ODP) in the Barycentric Celestial Reference System, in which the Sun moves around the centre of mass of the solar system with a velocity v ⊙ of about 10 m/sec; the question arises, what correction this implies for the predicted phase shift. After a review of the way the ODP works, we set the problem in the framework of Lorentz (and Galilean) transformations and evaluate the correction; it is several orders of magnitude below our experimental accuracy. We also discuss a recent paper [10], which claims wrong and much larger corrections, and clarify the reasons for the discrepancy.
Understanding the processes that led Venus to its current state and will drive its future evoluti... more Understanding the processes that led Venus to its current state and will drive its future evolution is a major objective of the next generation of orbiters. In this work we analyze the retrieval of the spin vector, the tidal response, and the moment of inertia of Venus with VERITAS, a NASA Discovery-class mission. By simulating a systematic joint analysis of Doppler tracking data and tie points provided by the onboard synthetic aperture radar, we show that VERITAS will provide accuracies (3σ) in the estimates of the tidal Love number k 2 to 4.6 × 10 −4 , its tidal phase lag to 0°. 05, and the moment of inertia factor to 9.8 × 10 −4 (0.3% of the expected value). Applying these results to recent models of the Venus interior, we show that VERITAS will provide much-improved constraints on the interior structure of the planet.
On October and December 2004 the Cassini spacecraft performed two flybys of Saturn\u2019s moon Ia... more On October and December 2004 the Cassini spacecraft performed two flybys of Saturn\u2019s moon Iapetus. Although the closest approach distance was large and the encounters barely deserve the name of flybys, they provided the first opportunity for an accurate determination of the satellite\u2019s mass and density. The good quality of the Cassini X-band Doppler data allowed a substantial reduction of the experimental uncertainty obtained with past measurements. The orbital fit of the spacecraft trajectory was carried out over arcs of 15 days about the closest approach and used a limited set of solve-for parameters. Our best estimate of the satellite\u2019s gravitational parameter results from the first and more distant flyby. The second flyby, occurring at a much closer distance, gave a smaller formal error and a rather consistent estimate, but the orbital solution was much more affected by the uncertainties in Iapetus ephemerides and likely to be biased
Microwave tracking, usually performed by on ground processing of the signals coming from a spacec... more Microwave tracking, usually performed by on ground processing of the signals coming from a spacecraft, represents a crucial aspect in every deep-space mission. Various noise sources, including receiver noise, affect these signals, limiting the accuracy of the radiometric measurements obtained from the radio link. There are several methods used for spacecraft tracking, including the Delta-Differential One-Way Ranging ( Δ DOR) technique. In the past years, European Space Agency (ESA) missions relied on a narrowband Δ DOR system for navigation in the cruise phase. To limit the adverse effect of nonlinearities in the receiving chain, an innovative wideband approach to Δ DOR measurements has recently been proposed. This work presents the hardware implementation of a new version of the ESA X/Ka Deep Space Transponder based on the new tracking technique named Wideband Δ DOR (W- Δ DOR). The architecture of the new transponder guarantees backward compatibility with narrowband Δ DOR.
Uploads
Papers by L. Iess