Bio

Affiliation: NASA Johnson Space Center in Houston, Texas
About the Speaker.
Timothy Kennedy is the Radar Lead for the Orbital Debris Program Office at the NASA Johnson Space Center in Houston, Texas. He received a bachelor's (summa cum laude), master's, and Ph.D. in electrical engineering from the University of Houston in 2001, 2003, and 2006 respectively. He joined the NASA Johnson Space Center in 2005 working in the areas of computational electromagnetics modeling, antenna systems, radar, and sensor development for multiple human spaceflight programs. Prior to joining NASA he was with the Geophysics group at Schlumberger in Sugar Land, Texas working on inverse problems in layered media and software development. He has numerous publications and 20 US Patents in the areas of antenna systems, cooperative radar, computational electromagnetics modeling, radar and sensor development. His recent interests are in applications of Bayesian inference and machine learning to radar detection and object recognition. He has received multiple NASA Patent awards, the Federal Laboratory Consortium Notable Technology Award, Space Act Board award, Johnson Space Center Director's Commendations, and the NASA Exceptional Technology Achievement Medal.

RADAR OBSERVATIONS OF THE ORBITAL DEBRIS ENVIRONMENT IN LOW EARTH ORBIT

Abstract

Currently there are more than 20,000 objects, approximately 10 cm and larger, tracked by the U.S. Space Surveillance Network (SSN). Due to the approximate power law relationship between the number of objects on orbit and the characteristic size of orbital debris, and the additional ground-based and in situ orbital debris measurement data available, the population of smaller orbital debris is even larger. Objects that have a characteristics size > 1mm represent significant risk to robotic spacecraft in LEO, and even smaller sizes pose significant risk to human missions. With population estimates exceeding 500,000 objects that are > 5 mm in low Earth orbit (LEO), it is currently not practical to track and maintain precision orbits on every object. To measure the distribution of smaller objects not tracked by the SSN, a statistical sampling approach to radar observations of the orbital debris environment is used. This talk describes the methods commonly applied for orbital debris radar observations, and the inferences that can made from these observations about the current environment.

Bio

Affiliation: Institut de Planetologie et d’Astrophysique de Grenoble (IPAG) University Grenoble Alpes - FRANCE
About the Speaker.
Alain Herique was born in 1968. He received the Engineer degree in signal processing from the Ecole Nationale Supérieure d’Ingénieur Electricien de Grenoble, France, in 1991 and and a PhD from the Institut National Polytechnique de Grenoble in 1995. He is currently an associate professor at the Institut de Planétologie et d'Astrophysique de Grenoble, Université Grenoble Alpes, France. From 1992 to 1998 he worked at the CEPHAG in Grenoble on penetrating radar applied to planetary sciences. From 1998-1999 he was a system engineer with Alcatel Space Industries in Toulouse and studied new concepts of X-Band SAR instrument for Earth Observation for ESA. In 1999 he joined the LPG (now IPAG). He is studying small bodies’ internal structure fathomed by radars. His scientific research field include electromagnetic simulation of surface scattering and wave propagation in the subsurface, radar science (system design and simulation, calibration), dielectric properties and data inversion (signal processing, SAR processing, tomography) applied to planetary subsurface sounding and small bodies tomography. He is involved in many planetary space missions. He is PI of the CONSERT experiment on board Rosetta/ESA (previously Co-I and thereafter Deputy-PI). He is Co-I of Reason / Europa Clipper (NASA), and Wisdom /Exomars (ESA) and team member of MARSIS/MEx, RIME/JUICE. He has participated in many proposals of missions for NASA, ESA and JAXA. He is PI of the LFR radar on board the HERA/AIDA mission proposed to ESA, and of the GRIFIN radar on board Chimera proposed to Discovery.

DIRECT OBSERVATIONS OF SMALL BODIES’ INTERIOR WITH RADAR ONBOARD PLANETARY PROBES.

Abstract

Despite some highly successful space missions to comets and asteroids, their internal structure remains largely unknown. Apart from CONSERT onboard Rosetta (ESA), which fathomed a limited part of the 67P/ Churyumov–Gerasimenko comet nucleus, our knowledge of the deep interior and shallow subsurface is based on theoretical modeling and on remote sensing observations of the surface. These questions are crucial to understand small bodies’ history from accretion in the early Solar System to the present. Radar onboard planetary probes is one of the most mature instruments capable to probe small bodies to characterize their internal structure from sub-meter to global scale. In this paper, we review the science case for direct observation of the deep internal structure and regolith of small bodies. We propose an instrument suite and its associated processing. We focus first on fathoming small bodies' regolith at higher resolution to understand the bodies' evolution processes, and then on probing the deep interior with a lower frequency bistatic radar to better model accretion/reaccretion processes. Bistatic radar for deep interior is illustrated with the CONSERT/Rosetta instrument and results. We then review the expected science return including secondary objectives, contributing to the determination of the gravitational field, the shape model, and the dynamical state. We then present programmatic perspectives in the frame of the Hera/ESA and Chimera/Discovery programs.

Bio

Space Science Institute, Boulder, Colorado and New Mexico Consortium, Los Alamos, New Mexico
About the Speaker.

My research efforts are driven by a desire to understand the physical mechanisms at work in the solarterrestrial environment. These mechanisms include direct particle-particle collisions (e.g. in the upper atmosphere) and waveparticle interactions in tenuous plasmas of the solar system (e.g. the solar wind). Recent research has focused on (i) the Earth's radiation belts, (ii) refilling processes in the ionosphere/plasmasphere, and (iii) empirical forecasting of particle populations in the inner magnetosphere. I have active research collaborations with scientists in various countries around the world.
Current Position(s): Research Scientist at Space Science Institute (since 2012) and New Mexico Consortium (since 2015).

• Previous Position(s): Senior Lecturer, Department of Physics, Lancaster University, UK, 2011- 2015.
• Lecturer, Department of Physics/Comms., Lancaster University, UK, 2006-2011.
• Research Fellow,Univ. Southampton, UK, 2006-2006.
• Research Associate, LANL, USA, 2003-2005.
• Research Assistant, Dept. of Physics, Uni. Wales, UK, 2000-2003.
• Ph.D. Thermal balance of the topside ionosphere, App. Math., Sheffield, UK, 2000.
• B.Sc. Physics, Dept. of Physics, University of Sheffield, UK, 1997.

UNSOLVED PROBLEMS IN PLASMASPHERIC PHYSICS

Abstract

The plasmasphere is a region of cold (~1 eV) plasma that forms from the up flow of ionospheric material on closed magnetic field lines.  In this colloquium, we present a brief history of plasmaspheric research, summarize our current understanding of plasmapheric dynamics, and discuss ground-based and space-based observations of the plasmasphere. We also outline the limits of our current knowledge of the plasmasphere and list outstanding science questions where our understanding is incomplete. Finally, we discuss potential new facilities/missions that could make progress on better understanding this important and dynamic region of the coupled Sun-Earth system.