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Picardi, G.

Publications and source records attributed to Picardi, G..

16 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2009

Is the Martian Water Table Hidden from Radar View?

Mars may possess a global sub-surface groundwater table as an integral part of its current hydrological system, However, the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) onboard the 'Mars Express (MEx) spacecraft has yet to make a definitive detection of such a body of liquid water. In this work, we quantify. the conditions that would allow a detection of a deep aquifer and demonstrate that the lack of radar detection doses not uniquely role out the presence of such a body. Specifically, if the overlying crustal material has a conductivity above approximately 10(exp -5) S/m (equivalent to a loss tangent of 0.008), a radar echo frown an aquifer could be sufficiently attenuated by the intetvening medium to prevent its detection by MARSIS. As such, the lack of direct detection by MARSIS -- a "null result" does not rule out the possibility of the water table's existence.

Farrell, W. M.↗
NASA NTRS2005

Cassini radar views the surface of Titan

The Cassini Titan Radar Mapper imaged about 1% of Titan's surface at a resolution of approximately 0.5 kilometer, and larger areas of the globe in lower resolution modes. The images reveal a complex surface, with areas of low relief and a variety of geologic features suggestive of dome-like volcanic constructs, flows, and sinuous channels. The surface appears to be young, with few impact craters. Scattering and dielectric properties are consistent with porous ice or organics. Dark patches in the radar images show high brightness temperatures and high emissivity and are consistent with frozen hydrocarbons.

Saturn↗
NASA NTRS2005

The MARSIS Science Mission

The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) is an integral component of the Mars Express mission. A low-frequency sounding radar was carried on the Russian Mars 96 spacecraft, and in keeping with the concept of re-flying the science experiments lost on that mission, a call for a radar sounder was part of the Announcement of Opportunity for the 2003 ESA Mars Express mission. MARSIS is the only totally new instrument on Mars Express. The instrument was developed, delivered and operated as a joint effort between the Italian Space Agency and the U.S space agency NASA. The MARSIS science mission has been delayed due to concerns about the safety of the antenna deployment. As a testament to the importance placed on the

Plaut, J J.↗
NASA NTRS2004

Mars Express: The Exploration of Phobos

The origin, structure and composition of Phobos are essentially still unresolved issue, with major outcomes for understanding the origin and evolution of the Solar system, and of the Mars system. Several missions have been designed with this unique body the only target. Is Phobos a captured small body (and in this case, can we identify the degree of differentiation such a small object has undergone ?), or is there any co-generic process with Mars involved ? Are there still volatile species trapped, and if so where, and in what form ? What are the reciprocal contributions of Mars and Phobos material accreted in the other body? The number of key clues for deciphering the early solar system processes, the Mars-Phobos binary evolution, and the role Phobos could play in the future of Mars exploration (including human expeditions), are numerous, and exciting for a large community. Part of the answers are in the high resolution coverage of this object (optical and IR, for composition variation), and in its full spectral analysis, from UV to thermal IR : Mars Express is the unique mission to provide this opportunity, and orbit 756, August 22, a totally unique opportunity to approach Phobos so closely. OMEGA should provide all across Stickney, the deepest accessible material, and over more than 20 km along, a spatial resolution less than 200 m, and assess the composition (and possibly their variations) wrt silicates (mafic materials), oxides, and eventually hydrated minerals and organics. By no means we should miss this opportunity: no one would understand the rationale not to turn the instruments ON while so close, and pointing them towards the Phobos surface.

Phobos↗
NASA NTRS2004

Mars Express MARSIS Radar: A Prediction of the Effect of Overlying Ice on Detecting Polar Basal Lakes and Inter-Glacial Aquifers

The penetration of the MARSIS radar signal into the polar ice mass is modeled to determine the capability of the instrument to locate sub-glacial aquifers. As a ground penetrating radar, the orbiting MARSIS transmits a signal greater than 1 W between 1-5 MHz. In this work we will investigate the effect of ice conductive losses on the radar-detection of subsurface aquifers. Based on wave propagation analysis, it is found that for a bulk ice conductivity below 10-5 S/m, conductive losses in the medium are not significant. However, if the bulk ice conductivity is relatively large (greater than 10-5 S/m), the reflected signal from any deep aquifer will be absorbed as it propagates in the lossy ice medium limiting the probing depth.

Farrell, W. M.↗
NASA NTRS2003

Probing the Subsurface of the Martian Polar Regions with MARSIS on Mars Express

The European Space Agency (ESA) is currently conducting a mission to Mars known as Mars Express. The orbiter carries an instrument called the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS). The MARSIS experiment is a joint project between NASA and the Italian Space Agency, and is being carried out by the University of Rome, the Jet Propulsion Laboratory, Alenia Aerospazio, and the University of Iowa. This paper describes the science objectives of the experiment, the instrument characteristics, and applications of the MARSIS investigation to studies of the martian polar regions.

Plaut, J. J.↗
NASA NTRS2002

MARSIS calibration plan

Explore the source record for details and available documents.

MARSIS calibration HF radar subsurface detection o↗
NASA NTRS2002

MARSIS calibration plan

Explore the source record for details and available documents.

MARSIS calibration HF radar subsurface detection o↗
NASA NTRS2001

Radar Sounding of Mars: A Focus on MARSIS

Radar has the unique capability of looking under the dry and cold surfaces of Mars. The depth of penetration of radio waves depends on a number of surface and subsurface parameters such as surface topography, subsurface geological structure and surface and subsurface electromagnetic properties. Among these parameters, the surface topography is known best largely due to valuable data provided by Mars Global Surveyor's MOLA instrument. However, little information is available on the electromagnetic properties and subsurface characteristics of Mars.

radar sounding↗
NASA NTRS2001

Radar Sounding of Mars: A Focus on MARSIS

Radar has the unique capability of looking under the dry and cold surfaces of Mars. The depth of penetration of radio waves depends on a number of surface and subsurface parameters such as surface topography, subsurface geological structure, and surface and subsurface electromagnetic properties. Among these parameters, the surface topography is known best largely due to valuable data provided by Mars Global Surveyor's MOLA (Mars Orbiter Laser Altimeter) instrument. However, little information is available on the electromagnetic properties and subsurface characteristics of Mars. In addition to dispersion, the ionosphere will also attenuate the radio wave. The level of attenuation depends on the ionosphere's electron density and its profile shape and the electron-neutral collision frequency. Fortunately, information from past missions can provide some information on the expected level of attenuation. A figure shows expected total radio wave attenuation under three different ionospheric conditions. Additional information is contained in the original extended abstract.

Safaeinili, A.↗
NASA NTRS2001

The System and Implementation Aspects of the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS)

MARSIS is a radar sounder operating in the HF frequency range to sound the surface of Mars, which will operate from the ESA Mars Express spacecraft. It is scheduled for launch from Baikonour, Russia in June 2003 and arrives in orbit around Mars in early 2004 for a two-year mission. This system is the result of an international collaboration between NASA, the Italian Space Agency (ASI), and European Space Agency (ESA). The MARSIS instrument is a 17 Kilogram total mass sounder consisting of a 40 meter tip-to-tip dipole antenna, a 7 meter long monopole antenna and the electronics module. This design of MARSIS is a tradeoff between the expected penetration into the Martian subsurface that is proportional to the wavelength of the system and the desire to operate at a short wavelength in order to minimize the effects of the ionosphere. Additional information is contained in the original extended abstract.

Jordan, R.↗