Synthetic aperture imaging at 1.5μ: laboratory demonstration and potential application to planet surface studies

Two-dimensional imaging with synthetic aperture ladar (SAL) has been demonstrated in the laboratory. The method is entirely analogous to scan-mode synthetic aperture radar (SAR), which was used on the Magellan mission to Venus, but with 104-5 times shorter wavelength has the potential for much better resolution. The laboratory experiment is described and the theoretical limits placed on SNR by the combination of photon statistics and laser speckle are stated. SAL's limitations of small ground footrpint size and SNR < 1 for single-look imagery can be alleviated by multiple images and mosaicking of scenes. Design equations are given that show what hardware capabilities are needed to implement a desired system. They show that a 10 μ SAL in orbit around Mars can give centimeter-class resolution with reasonable laser power (≤ 100 wt). Major engineering development hurdles must be overcome before any such system can be built.