Engineering topics
Lebreton, Jean-Pierre
Publications and source records attributed to Lebreton, Jean-Pierre.
Using Schumann Resonance Measurements for Constraining the Water Abundance on the Giant Planets - Implications for the Solar System Formation
The formation and evolution of the Solar System is closely related to the abundance of volatiles, namely water, ammonia, and methane in the protoplanetary disk. Accurate measurement of volatiles in the Solar System is therefore important to understand not only the nebular hypothesis and origin of life but also planetary cosmogony as a whole. In this work, we propose a new, remote sensing technique to infer the outer planets water content by measuring Tremendously and Extremely Low Frequency (TLF-ELF) electromagnetic wave characteristics (Schumann resonances) excited by lightning in their gaseous envelopes. Schumann resonance detection can be potentially used for constraining the uncertainty of volatiles of the giant planets, mainly Uranus and Neptune, because such TLF-ELF wave signatures are closely related to the electric conductivity profile and water content.
Highly Structured Plasma Density and Associated Electric and Magnetic Field Irregularities at Sub-Auroral, Middle, and Low Latitudes in the Topside Ionosphere Observed with the DEMETER and DMSP Satellites
Detailed observations of the plasma structure and irregularities that characterize the topside ionosphere at sub-auroral, middle, and low-latitudes are gathered with probes on the DEMETER and DMSP satellites. In particular, we present DEMETER observations near 700 km altitude that reveal: (1) the electric field irregularities and density depletions at mid-latitudes are remarkably similar to those associated with equatorial spread-F at low latitudes; (2) the mid-latitude density structures contain both depletions and enhancements with scale lengths along the spacecraft trajectory that typically vary from 10's to 100's of km; (3) in some cases, ELF magnetic field irregularities are observed in association with the electric field irregularities on the walls of the plasma density structures and appear to be related to finely-structured spatial currents and/or Alfven waves; (4) during severe geomagnetic storms, broad regions of nightside plasma density structures are typically present, in some instances extending from the equator to the subauroral regions; and (5) intense, broadband electric and magnetic field irregularities are observed at sub-auroral latitudes during geomagnetic storm periods that are typically associated with the trough region. Data from successive DEMETER orbits during storm periods in both the daytime and nighttime illustrate how enhancements of both the ambient plasma density, as well as sub-auroral and mid-latitude density structures, correlate and evolve with changes in the Dst. The DEMETER data are compared with near simultaneous observations gathered by the DMSP satellites near 840 km. The observations are related to theories of sub-auroral and mid-latitude plasma density structuring during geomagnetic storms and penetration electric fields and are highly germane to understanding space weather effects regarding disruption of communication and navigation signals in the near-space environment.
The Huygens Mission to Titan: Overview and Status
A general overview and status of the Huygens Mission to Titan is presented.
Cassini-Huygens in Orbit Around Saturn
The Cassini-Huygens spacecraft was successfully placed in an orbit about Saturn on June 30, 2004. Starting with our approach to Saturn, the instruments carried by the Orbiter have been very active since early 2004. The Huygens probe mission was also recently completed. As a result, all of the Cassini Orbiter investigations and Huygens Probe investigations have scientific results to report.
The Cassini/Huygens Flyby of Jupiter
At the and of the year 2000 the Cassini/Huygens spacecraft will fly by the planet Jupiter at a range of 137 jovian radii. A preliminary assessment has indicated that the instruments aboard Cassini/Huygens can make measurements that will make unique contributions to audio of the jovian system. In this presentation we will discuss the status of the plans for observations of the jovian system by Cassini/Huygens. We shall also consider the possibilities for observations carried out in cooperation with the Galileo spacecraft presently in orbit about Jupiter, with other spacecraft, and with various observatories on the ground.
Charged body-plasma interaction research laboratory for the International Space Station
An experiment is proposed for the provision of a fundamental plasma physics facility onboard the International Space Station (ISS) for the investigation of the plasma processes governing the electron current collection processes on a charged electrode. The facility will allow the pre-sheath and sheath physics of a positively biased body to be investigated. These processes are important to the consideration of the use of electrodynamic tether lines for practical applications such as for electrical power generation and to the understanding of the physics of space plasma. A deployment mechanism is required to deploy the charged body to a distance of several 100 m from the space station. The possible solutions are a flexible boom or a short tether line.
Cassini: Mission to Saturn and Titan
The Cassini Mission to Saturn and Titan represents an important step into the exploration of the outerplanets. It will expand on the flyby encounters of Pioneer and Voyager and parallel the detailed exploration of the Jupiter system to be accomplished by the Galileo Mission. By continuing the study of the two giant planets and enabling detailed comparisons of their structure and behavior, Cassini will provide a tremendous insight into the formation and evolution of the solar system. In addition, by virtue of its focus on the Saturnian satellite Titan, Cassini will return detailed data on an environment whose atmospheric chemistry may resemble that of the primitive Earth. The scientific objectives can be divided into five categories: Titan, Saturn, rings, icy satellites, and magnetospheres. The key area of interest to exobiologists is Titan; the other four scientific categories will be discussed briefly to provide a comprehensive overview of the Cassini Mission.
The CRAF/Cassini science instruments, spacecraft, and missions
The first two missions planned for the Mariner Mark II spacecraft, the Cassini mission and the Comet Rendevous Asteroid Flyby (CRAF), are described, along with the Mariner Mark II spacecraft and the instruments that will be used for the two missions. The chief goals of the CRAF mission include determinations of the elemental, molecular, isotopic, and mineralogic compositions and the physical, morphological, and geological character of the cometary nucleus, as well as the characterization of changes occurring as functions of time and orbital position. The Cassini mission will determine the elemental, molecular, isotopic, and mineralogic compositions of Saturn, Titan, the smaller moons, and the rings of the Saturnian system and determine the physical, morphological, and geological nature of these objects; it will also determine the processes operating in the atmospheres of Saturn and Titan and on the surfaces of the rings and satellites of the system and determine the properties of Saturn's magnetosphere and its interactions with the rings and the moons of Saturn.