Performance results of the SHARAD instrument

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. The design of the instrument reflect a balance of scientific requirements versus SHARAD mission and Hardware constraints. One of the most difficult point in SHARAD design was the choice of the radar wavelength, since longer wavelengths have the potential for deeper subsurface penetration at the expense of depth resolution. Shorter wavelengths enhance the ability to generate surface images and accurate profile. A radar sounder needs a system requirements for large dynamic range and precise sidelobe control. Very low range side-lobes are mandatory to allow detection of weak sub-surface echoes in presence of the strong surface return. The approach of limiting to the minimum the amount of processing performed on-board was selected in order to allow the pulse compression process (critical from the point of view of range side-lobes) to be performed on ground, using the computed instrument Point-Target-Response (PTR) as correlation reference waveform. One of the main goal of this paper is to describe the design of the experiment design of SHARAD and the selection of the instrument parameters. An assessment of radar performance has been obtained by using both on-ground and on- flight measurements. Some preliminary results from the mars mission have been reported.