Impulse scattering function for a dielectric cylinder?

Hi, I'm new in this forum, I hope you can help me with my problem:

What means impulse scattering function, is that the RCS over the frequency of the object?
Wich method is better to aproach this scattering problem, method of moments or finite Difference/Elements, supposing and homogeneous dielectric cylinder? Is there any numerical technique more suitable for the simulation?

Please include any useful explanation to understand the choice. Thanks in advance.?