707 research outputs found
Mars ionosphere TEC estimation from MARSIS data: A new approach
No full textInternational audienceWe describe a new implementation of the Contrast Method (CM) algorithm (Picardi and Sorge, 2000; Ilyushin Ya and Kunitsyn, 2004; Cartacci et al., 2013) used to correct the phase distortion of the echoes recorded by the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) (Picardi et al., 2005; Jordan et al., 2009) in its subsurface mode.The New CM is designed following an improved approach which allows not only to perform its original task but also to estimate the Total Electron Content (TEC) of the Mars ionosphere with a better accuracy respect to the past (Cartacci et al., 2013; Cartacci et al., 2017), in the nightside when the transmitted frequency is close to the ionosphere plasma frequency as well as in the dayside, thanks to a lesser use of theoretical approximations in the method development.Moreover, taking advantage of almost 16 years of MARSIS operations, corresponding to about 8700 orbits, we present an improved global map of the night side TEC variations due to the interaction with the Mars crustal magnetic field (Safaeinili et al., 2007; Cartacci et al., 2013)
Surface and subsurface radar backscattering coefficient over the Martian South Polar Layered Deposits from MARSIS data
No full textMars ionosphere TEC estimation from MARSIS data: A new approach
No full textWe describe a new implementation of the Contrast Method (CM) algorithm (Picardi and Sorge, 2000; Ilyushin Ya and Kunitsyn, 2004; Cartacci et al., 2013) used to correct the phase distortion of the echoes recorded by the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) (Picardi et al., 2005; Jordan et al., 2009) in its subsurface mode. The New CM is designed following an improved approach which allows not only to perform its original task but also to estimate the Total Electron Content (TEC) of the Mars ionosphere with a better accuracy respect to the past (Cartacci et al., 2013; Cartacci et al., 2017), in the nightside when the transmitted frequency is close to the ionosphere plasma frequency as well as in the dayside, thanks to a lesser use of theoretical approximations in the method development. Moreover, taking advantage of almost 16 years of MARSIS operations, corresponding to about 8700 orbits, we present an improved global map of the night side TEC variations due to the interaction with the Mars crustal magnetic field (Safaeinili et al., 2007; Cartacci et al., 2013).</p
MARSIS over Elysium Planitia: mapping a subsurface structure in an area with a complex geological history.
No full text
Studio della produzione inclusiva di adroni nelle collisioni a LEP
No full textDottorato di ricerca in fisica. 8. ciclo. Relatore A. M. Cartacci. Relatore G. GiacomelliConsiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7, Rome; Biblioteca Nazionale Centrale - P.za Cavalleggeri, 1, Florence / CNR - Consiglio Nazionale delle RichercheSIGLEITItal
Improved estimation of Mars ionosphere total electron content
No full textWe describe an improved method to estimate the Total Electron Content (TEC) of the Mars ionosphere from the echoes recorded by the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) (Picardi et al., 2005; Orosei et al., 2015) onboard Mars Express in its subsurface sounding mode. In particular, we demonstrate that this method solves the issue of the former algorithm described at (Cartacci et al., 2013), which produced an overestimation of TEC estimates on the day side.
The MARSIS signal is affected by a phase distortion introduced by the Mars ionosphere that produces a variation of the signal shape and a delay in its travel time. The new TEC estimation is achieved correlating the parameters obtained through the correction of the aforementioned effects.
In detail, the knowledge of the quadratic term of the phase distortion estimated by the Contrast Method (Cartacci et al., 2013), together with the linear term (i.e. the extra time delay), estimated through a radar signal simulator, allows to develop a new algorithm particularly well suited to estimate the TEC for solar zenith angles (SZA) lower than 95° The new algorithm for the dayside has been validated with independent data from MARSIS in its Active Ionospheric Sounding (AIS) operational mode, with comparisons with other previous algorithms based on MARSIS subsurface data, with modeling and with modeling ionospheric distortion TEC reconstruction
Permittivity estimation of layers beneath the northern polar layered deposits, Mars
No full textMartian Polar Layered Deposits, most likely dusty ice
are transparent to radar waves. In the North Pole bedrock
has been detected by MARSIS up to a depth about 2 Km,
whereas in the South Pole such interface has been located
at about 3.7 Km. The reflected signal is generally above
the noise and can be used to estimate the dielectric properties
of the bedrock. Assuming the permittivity of the first layer is
known, we use a simplified inversion method to extract the
bedrock relative dielectric permittivity as 4–9 below the
North PLD’s. These values are coherent with the basalt
nature and so the approach could be used to identify the
lithology beneath the Martian Poles
Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) after nine years of operation: a summary
No full textMars Express, the first European interplanetary mission, carries the Mars Advanced Radar for Subsurface
and Ionosphere Sounding (MARSIS) to search for ice and water in the Martian subsurface. Developed by
an Italian–US team, MARSIS transmits low-frequency, wide-band radio pulses penetrating below the
surface and reflected by dielectric discontinuities linked to structural or compositional changes. MARSIS
is also a topside ionosphere sounder,transmitting a burst of short, narrow-band pulses at different
frequencies that are reflected by plasma with varying densities at different altitudes.The radar operates
since July 2005, after the successful deployment of its 40 m antenna, acquiring data at altitudes lower
than 1200 km. Subsurface sounding (SS)data are processed on board by stacking together a batch of
echoes acquired at the same frequency. Onground, SS data are further processed by correlating the
received echo with the transmitted waveform and compensating de-focusing caused by the dispersive
ionosphere. Ground processing of active ionospheric sounding (AIS)data consists in the reconstruction
of the electron density profile as a function of altitude. MARSIS observed the internal structure of Planum
Boreum outlining the Basal Unit, an icy deposit lying beneath the North Polar Layered Deposits thought
to have formed in an epoch in which climate was markedly different from the current one.The total
volume of ice in polar layered deposits could be estimated, and parts of the Southern residual ice cap
were revealed to consist of 10 m of CO2 ice. Radar properties of the Vastitas Borealis Formation point
to the presence of large quantities of ice buried beneath the surface. Observations of the ionosphere
revealed the complex interplay between plasma, crustal magnetic field and solar wind, contributing to
space weather studies at Mars. The presence of three-dimensional plasma structures in the ionosphere
was revealed for the first time. MARSIS could successfully operate at Phobos, becoming the first
instrument of its kind to observe an asteroid-like body. The main goal pursued by MARSIS, the search for
liquid water beneath the surface, remains elusive. However, because of the many factors affecting
detection and of the difficulties in identifying water in radar echoes, a definitive conclusion on its
presence cannot yet be drawn
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