slide 29

The key idea is that the length of a weapon determines how deeply it can penetrate. X-Band radar cannot penetrate tree canopies, but C-Band can penetrate slightly deeper without reaching the canopy. L-Band can penetrate the canopies and measure the ground below. Longer wavelengths like L-Band are useful for measuring surface displacement without vegetation interference, but they have lower range resolution. Shorter wavelengths like X-Band are better for urban monitoring due to higher range resolution. Different radar bands have different applications based on their characteristics. The main characteristics can be summarized into one sentence. The longer the weapon, the deeper the penetration. You can see the figure. In terms of vegetation, X-Band cannot penetrate the canopy of the tree, so it bounces back to the receiver. C-Band penetrates a little deeper than X-Band, but it still cannot penetrate the canopy. L-Band is able to penetrate the canopy, and then penetrate again the canopy towards the satellite. So, using the longer wavelength, such as L-Band, P-Band, can allow us to measure the ground below the tree or vegetation. In the InSight application, using L-Band or longer wavelength can let us measure the surface displacement without strong vegetation effects. However, it doesn't mean longer wavelength data is better than shorter wavelength. The obvious drawback is the close range resolution. The bandwidth of the longer wavelength is large, so the range resolution decreases. If you want to measure the city, it is recommended to use the shorter wavelength due to the complex urban buildings. You can look back to the last slide. With the characteristics introduced here, you can understand why different bands have different applications. For instance, X-Band is mainly used for urban monitoring because of the higher range resolution.