Range resolution enhancement of SHAllow RADar (SHARAD) data via bandwidth extrapolation technique: Enabling new features detection and improving geophysical investigation

• Published in: Icarus
• Main Authors: M. C Raguso , M. Mastrogiuseppe, L. Gambacorta, G. Di Achille, R. Seu
• Other Authors: M. Mastrogiuseppe, M. C Raguso, Gambacorta, L., Di Achille, G., Seu, R.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Academic Press Inc. 2023
• Subjects: interior; Mar; radar observation; resolution enhancement; SHARAD; stratigraphy; Ice cap
• Online Access: https://hdl.handle.net/11573/1699089; https://doi.org/10.1016/j.icarus.2023.115803

Abstract The SHAllow RADar (SHARAD) is a subsurface sounding radar provided by the Italian Space Agency (ASI) as a facility instrument for NASA's Mars Reconnaissance Orbiter (MRO) mission, the second longest-lived mission to orbit Mars after Mars Odyssey. Developed by an Italian-US Team, SHARAD was designed to investigate to depth of up to one kilometer in the Martian subsurface and to map dielectric discontinuities associated with compositional and/or structural changes. The radar mapping began in November 2006 and, after 16 years of operations, SHARAD has mapped most of the planet's surface (∼55%), contributing a data volume for the entire MRO mission that exceeds that of all the past Mars missions combined. Designed to complement the lower-frequency, relatively narrower bandwidth capability of the MARSIS sounding radar, SHARAD emits an 85 , frequency-modulated (10 MHz) chirp at a central frequency of 20 MHz to increase the signal-to-noise ratio (SNR) and achieve a finer resolution compared to MARSIS. On the ground, echoes recorded by the radar are range compressed using conventional pulse compression techniques yielding a nominal range resolution of 15 m (vacuum, 5–8 m in typical Martian materials). Additionally, synthetic aperture processing is performed in along-track to increase the resolution up to 300–500 m. Throughout the entire mission duration, SHARAD provided a diverse and extensive range of imaging data. It was able to observe the internal structures of Planum Boreum and Planum Australe, two icy deposits that contain the North and South Polar Layered Deposits (NPLD-SPLD), thought to contain valuable information about the planet's past climate. The radar unveiled the massive deposits of buried CO2 ice below the southern residual ice cap (SRIC), which confirmed the influence of the planet obliquity and insolation in the accumulation of dry ice. Furthermore, it revealed the intricate lava flows structures in the Tharsis Volcanic region, suggesting that the planet experienced deposition by multiple ...