Low-Frequency, All Digital Radar (ADR) can be a key component for NASA Phased-array and tomographic Radar systems spanning multiple earth-science measurement objectives. One of the key attractions of ADR is hardware re-use for different scenarios. Intelligent Automation Inc. (IAI) proposes the design of an ADR system to meet the technology requirements listed in this solicitation. State-of-the-art technologies in the design of data conversion devices like Analog-to-Digital Converters (ADC), Digital-to-Analog Converters (DAC), Direct Digital Synthesizers (DDS) and reconfigurable logic devices like Field Programmable Gate Arrays (FPGA) MMIC make it possible to realize the concept of ADR with low SWaP and low-cost goals. The proposed ADR will build upon IAI's Software Defined Radio/ Radar (SDR) design expertise. Our proposed approach is modular, scalable and meets the NASA goals of multi-channel, coherent altimeters along the cross track to obtain high resolution in the cross track direction.