Subsurface Detection in SHARAD Mission
- Paper number
IAC-07-A5.I.-A3.I.B.06
- Author
Mr. Franco Fois, Alcatel Alenia Space Italia, Italy
- Coauthor
Claudio Catallo, Thales Alenia Space, Italy
- Coauthor
Riccardo Mecozzi, Thales Alenia Space, Italy
- Coauthor
Mr. Marco Iorio, Alcatel Alenia Space Italia, Italy
- Coauthor
Dr. Enrico Falmini, Italian Space Agency (ASI), Italy
- Coauthor
Mr. Roberto Seu, University of Rome "La Sapienza", Italy
- Year
2007
- Abstract
SHARAD (SHAllow RADar) is a subsurface sounding radar provided by ASI as a Facility Instrument to NASA’s 2005 Mars Reconnaissance Orbiter for the characterization of the upper part of the Martian crust. SHARAD is a low frequency (20MHz center frequency) Ground Penetrating Radar (GPR) in altimeter configuration which uses the synthetic aperture technique. The instrument has a vertical resolution of 15m and an along track resolution of 300m spatial with a penetrating capability of about 2Km. Data acquired from the Martian surface are processed in range and azimuth dimension to produce the scientific final data. Commonly the scientific data are presented with a classical altimeter image that is a strip echoes collection in along track dimension (the orbital trace of the sensor). This strip image is called radargram and generally shows the surface echo line in along track dimension, the surface clutter in ground range dimension and eventually the subsurface echo presence. The first step to the data set interpretation above mentioned is the capability to discriminate the subsurface echo from the surface echo (clutter component). In this work two different methodologies are illustrated to the purpose of detect the subsurface presence in the data collection. These procedures use the available surface topography well known by previously mission on Mars planet (MOLA data derived by an optical altimeter instrument). The first technique is based upon the incoherent evaluation of the signal surface received from the instrument using the surface topography and in according with the classical backscattering model. The other approach uses the coherent analytical model to determinate a set of surface simulated data considering the MOLA surface information as a discrete surface data set and applying an opportunely facet model. Obviously both the above procedures to subsurface detection generates a synthetic simulated image that takes into account only the surface signal contribution (surface clutter) that can be directly compared with the experimental image. After a detailed discussion and extrapolation of the subsurface data, detection techniques will be illustrated. By considering the synthetic images together with the surface topography and the surface slope (obtained as a mathematical derivative of the surface profile) a fusion data methodology can be obtained: this is a very potential technique. In addition will be proposed the use of the synthetic topography besides to the real, this allows to take in to account the possible presence of a small scale scattering term that results not visible from the MOLA surface topography. An interesting application will be presented, in particular an incoherent and coherent image of Mars planet will be generated along an opportunely selected orbit for the SHARAD instrument. Finally the attention will be concentrated on particular surface topography portion of the Mars, to demonstrate the capabilities of the fusion technique to discriminate the subsurface presence from the surface echo contribution.
- Abstract document
- Manuscript document
IAC-07-A5.I.-A3.I.B.06.pdf (🔒 authorized access only).
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