Numerical algorithms capable of generating synthetic radio tomography data (reflection transmission data) for asteroids, comets, and other near-Earth orbits (NEOs) were developed. Future missions to main asteroid belt objects, NEOs, and other small bodies of the solar system will aim to investigate the surface and subsurface compositions and internal structure of these objects with help of an onboard, low-frequency radio sounder. The resulting numerical model thus developed will be useful in performing trade studies required for designing an optimum radio sounder for the future missions. The forward numerical model will also be important for estimating structural properties of the small objects from the data collected by these future missions.
In a space mission setting, an RF sounder orbiting at a safe stand-off distance from a small body will illuminate the target with low-frequency radio waves and will record the reflected signal from the target. If the RF frequency is low enough, part of the incident energy will also pass through the interior of the target and will be detected by the receiver on the lander located on the opposite side. From the observed reflected and transmitted signals, and using tomography techniques, it is possible to “see” the internal structure of the target along with its electrical properties. It is also desirable to check the performance of the RF sounder before its deployment.
For development of numerical simulation models to generate synthetic radio reflection-transmission data, the present technology uses a standard finite element method procedure. It is capable of handling any arbitrariness in small-body asteroids. Furthermore, because of division of the entire volume of the target into small tetrahedrons with control for adjusting their electrical properties independently, it is possible to handle highly inhomogeneous targets very efficiently. The numerical model allows observation of the performance of RRTT instruments as a function of various critical radar parameters.
This work was done by Manohar Deshpande of Goddard Space Flight Center. GSC-16434-1