Future NASA Earth Science mission concepts, such as the Surface Topography and Vegetation (STV) targeted observations, are increasingly relying on flexible observation strategies that utilize multiple lower cost instrument platforms to provide both global, frequent, and systematic coverage as well as rapid acquisition of high-resolution data for priority target areas. We are developing AIRSAR-NG, the next generation airborne synthetic aperture radar system, to replace the aging UAVSAR system to support STV incubation and future missions that leverage multi-static radar imaging techniques. AIRSAR-NG utilizes the software defined radar technology developed by our IIP-21 FLEXDSAR task which forms the backbone of the new radar with onboard digital beamforming as well as cross platform radar timing synchronization and calibration capabilities. A new DSI task will support the development of a second copy of the L-band AIRSAR-NG radar to enable us to conduct cross-platform airborne multi-static SAR imaging experiment. The multi-static SAR system will enable us to demonstrate tomographic SAR observation for forest structure monitoring using NISAR as the transmitting radar and the two airborne radars as the Receive-Only co-flyers. The dual-platform SAR system will also enable us to capture both forward and backscattered radar signals to differentiate between the relative contributions of vegetation and soil moisture. We also plan to take advantage of the L-band interferometric radar’s ability to penetrate vegetation to map the topographic change beneath forest canopy, which could be very useful in assessing landslide risk and other subcanopy land surface changes.