A Dual-Frequency Radio Occultation of Ganymede’s Ionosphere with Juno
No abstract provided
Bolton, S.↗
Engineering topics
Tortora, P.
Publications and source records attributed to Tortora, P..
The Europa Clipper Gravity / Radio Science Investigation
Introduction: The Jovian moon Europa has long been a fascinating planetary body because of its young icy surface and subsurface ocean. Its high appeal for astrobiology and habitability implications in the solar system and beyond have made it the subject of intense scientific inquiry and of many past mission studies. The NASA flagship Europa Clipper mission [1] is currently in development and slated to launch in 2024. After insertion into the Jupiter system, it will conduct more than 40 flybys of Europa over the course of several years [2]. The suite of nine science instruments is uniquely suited to this flyby tour strategy, providing remote sensing and in situ observations of Europa and its relationship to Jupiter [3]. The primary objective of Europa Clipper is to assess the habitability of Europa, an overarching goal that rests on improving our understanding of Europa’s interior structure, composition, and geologic activity. Here we describe the Gravity/Radio Science (G/RS) investigation of Europa Clipper, which will make important observations to address key science goals.
Pappalardo, R. T.↗
The Determination of Titan Gravity Field from Doppler Tracking of the Cassini Spacecraft
In its tour of the Saturnian system, the spacecraft Cassini is carrying out measurements of the gravity field of Titan, whose knowledge is crucial for constraining the internal structure of the satellite. In the five flybys devoted to gravity science, the spacecraft is tracked in X (8.4 GHz) and Ka band (32.5 GHz) from the antennas of NASA's Deep Space Network. The use of a dual frequency downlink is used to mitigate the effects of interplanetary plasma, the largest noise source affecting Doppler measurements. Variations in the wet path delay are effectively compensated by means of advanced water vapor radiometers placed close to the ground antennas. The first three flybys occurred on February 27, 2006, December 28, 2006, and June 29, 2007. Two additional flybys are planned in July 2008 and May 2010. This paper presents the estimation of the mass and quadrupole field of Titan from the first two flybys, carried out by the Cassini Radio Science Team using a short arc orbit determination. The data from the two flybys are first independently fit using a dynamical model of the spacecraft and the bodies of the Saturnian system, and then combined in a multi-arc solution. Under the assumption that the higher degree harmonics are negligible, the estimated values of the gravity parameters from the combined, multi-arc solution are GM = 8978.1337 +/- 0.0025 km(exp 3) / s(exp 2), J (sub 2) = (2.7221 +/- 0.0185) 10 (exp -5) and C (sub 22) = (1.1159 +/- 0.0040) 10 (exp -5) The excellent agreement (within 1.7 sigma) of the results from the two flybys further increases the confidence in the solution and provides an a posteriori validation of the dynamical model.
Iess, L.↗
Gravity Fields and Interiors of the Saturnian Satellites
This viewgraph presentation reviews the Gravity Science Objectives and accomplishments of the Cassini Radio Science Team: (1) Mass and density of icy satellites (2) Quadrupole field of Titan and Rhea (3) Dynamic Love number of Titan (4) Moment of inertia of Titan (in collaboration with the Radar Team) (5) Gravity field of Saturn. The proposed measurements for the extended tour are: (1) Quadrupole field of Enceladus (2) More accurate measurement of Titan k2 (3) Local gravity/topography correlations for Iapetus (4) Verification/disproof of "Pioneer anomaly".
gravity↗
Interiors of Enceladus and Rhea
Measurement method and data set: Gravity field parameters determined by means of range rate measurements over multiple arcs across flyby. Optical imaging not required when reliable a priori estimates of spacecraft state vector are available. Interior of Enceladus: Density of 1605 +/-14 kg/cu m, higher than pre-Cassini estimates, requires a substantial amount of rock to warmer interior to enhance likelihood of differentiation of water from rock-metal. Assume no porosity. Assuming Io s mean density for the rock-metal component, one finds its fractional mass to be 0.52+/-0.06. There is evidence that Enceladus may be differentiated: a) Areas devoid of craters must be geologically young. b) Systems of ridges, fractures, and groove indicate that the surface has been tectonically altered. c) Viscous relaxation of craters has occurred, and d) The plumes near the South pole indicate venting of subsurface volatiles.
gravity fields↗
Precision of radio science instrumentation for planetary exploration
The Deep Space Network is the largest and most sensitive scientific telecommunications facility Primary function: providing two-way communication between the Earth and spacecraft exploring the solar system Instrumented with large parabolic reflectors, high-power transmitters, low-noise amplifiers & receivers.
Radio Science Recever↗
Cassini navigation during solar conjunctions via removal of solar plasma noise
The Cassini spacecraft and its ground segment are currently testing a novel radio frequency multilink technology to perform radio science experiments.
navigation↗
Cassini navigation during solar conjunctions via removal of solar plasma noise
In this paper the steps required to compute a "plasma free" observable are described and discussed in detail.
orbit↗
The Cassini Gravitational Wave Experiment
Doppler tracking experiments using the earth and a distant spacecraft as separated test masses have been used for gravitational wave searches in the low-frequency band. Here we describe the experiment, including the transfer functions of the signals and noises to the Doppler observable, and present the noise statistics and compare them with the pre-experiment noise budget.
gravitational↗