SHARAD sounding radar on the Mars Reconnaissance Orbiter

Abstract

[1] SHARAD (SHAllow RADar) is a sounding radar provided by Agenzia Spaziale Italiana (ASI) as a Facility Instrument on the Mars Reconnaissance Orbiter mission. Its 20-MHz center frequency and 10-MHz bandwidth complement the lower-frequency, relatively narrower bandwidth capability of the MARSIS sounding radar. A joint Italian-U.S. team has guided the experiment development and is responsible for data analysis and interpretation. The radar transmits signals at a 700 Hz pulse repetition frequency (PRF) and collects reflections from both the surface and near subsurface of Mars. Vertical and horizontal resolutions are, respectively, 15 m (free-space) and 3-6 km (cross-track) by 0.3-1 km (along-track). The scientific objective of SHARAD is to map, in selected locales, dielectric interfaces to at least several hundred meters depth in the Martian subsurface and to interpret these results in terms of the occurrence and distribution of expected materials, including competent rock, soil, water, and ice. A signal-to-noise ratio of $50 dB (for a specular surface return) is achieved with 10 W of radiated power by using range and azimuth focusing in ground data processing. Preprocessed data as well as range-and azimuth-focused data will be formatted according to Planetary Data System (PDS) standards and be made available from the ASI Science Data Center (ASDC) and from the Geosciences Node of the Planetary Data System (PDS). Important targets for SHARAD include the polar layered deposits, sedimentary stacks (especially in Terra Meridiani), buried channel systems, buried impact craters, volcanic complexes, and shallow ice deposits in equilibrium with the atmosphere.

Shallow radar (SHARAD) sounding observations of the Medusae Fossae Formation, Mars

“…SHARAD operates at a center frequency of 20 MHz (λ = 15 m) with a 10 MHz bandwidth (Seu et al, 2004(Seu et al, , 2007a. With a nominal vertical resolution of 15 m in free-space, and 5-10 m vertical resolution in common geologic materials, SHARAD is capable of discerning thin subsurface layers.…”

“…With a nominal vertical resolution of 15 m in free-space, and 5-10 m vertical resolution in common geologic materials, SHARAD is capable of discerning thin subsurface layers. The lateral resolution of SHARAD is 3 to 6 km, reducible to 300 to 1000 m in the along-track direction with synthetic aperture focusing (Seu et al, 2004(Seu et al, , 2007a.…”

“…For smooth surfaces, the cross-track resolution is ∼750 m (Seu et al, 2007a). On the ground, the data are correlated with the radar chirp and spacecraft orbital information is used to determine the range relative to a topographic reference, in this case a biaxial ellipsoid with dimensions equal to the polar and equatorial radii of Mars.…”

Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) after nine years of operation: A summary

“…Stratalike linear features within the SPLD were noted by both Plaut et al (2007b) and Farrell et al (2008), but their interpretation in terms of reflections from distinct and sharp ice-ice interfaces of varying impurity content is countered by the finding that, in some places, the depth of the layers changes when examining two different MARSIS frequency bands. Milkovich et al (2009) studied the stratigraphy of Promethei Lingula in the SPLD, using both MARSIS and SHARAD (Seu et al, 2007) radar data. It was found that, within this region, reflections detected by MARSIS correlated with layer packets observed in images, while in tenfold higher resolution SHARAD data it could be seen that an individual reflection corresponded to 3-7 layers in images at resolutions of 6 m/pixel.…”

Permittivity estimation of layers beneath the northern polar layered deposits, Mars

“…[3] Both the North [e.g., Picardi et al, 2005;Putzig et al, 2009] and the South [e.g., Plaut et al, 2007;Seu et al, 2007a] PLD's have been observed by the MARSIS [Picardi et al, 2004] and SHARAD [Seu et al, 2007b] subsurface sounding radars, which operate in the HF and VHF bandwidth, respectively. Subsurface radar sounding is the only viable technique that can provide information in the third dimension (depth) of a planet from orbit.…”