Turing Reference

SHARAD description. The Shallow Radar (SHARAD) (S1) on the Mars Reconnaissance Orbiter spacecraft has a 20 MHz center frequency (15 m free-space wavelength, or ~ 9 m in water ice) and chirp bandwidth of 10 MHz yielding a one-way range resolution of 15 m divided by the square root of the real part of the permittivity of the propagation medium. The radar transmits a 10-W, 85-msec chirped (linear FM) pulse from a 10-m dipole antenna at a pulse repetition frequency of 700 Hz. MRO’s altitude ranges from ~250 km to ~315 km. The first Fresnel zone for a smooth, flat surface is ~3 km in diameter. Data shown here were processed with a focused synthetic aperture radar (SAR) technique to obtain an along-track resolution of ~300 meters. Depth conversions assume a permittivity (real part) of 3.2, a value consistent with a composition of water ice at typical Mars temperatures (S2). Clutter Simulation. Surface echoes were simulated using a facet-based, geometrical optics model (S3). Inputs consist of the Mars Orbiting Laser Altimeter (MOLA) 1/128 degree-per-pixel gridded radius data (S4) and th