Lightweight robotic excavators address the need for machines that dig, collect, transport and dump lunar soil. Robust and productive small robots enable mining rich and accessible deposits of ice and other volatiles buried near craters at the lunar poles, delivering resources to produce propellant, and thus making space exploration sustainable. Lightweight excavators bridge the gap between prospecting and full-scale ISRU. A lightweight robot is proposed that excavates and delivers regolith with production so superior to the state of the art as to enable realistic lunar and planetary applications. Demonstration of light weight will be achieved by operating a low mass robot in Earth gravity reduced 5/6 by offloading. The significance of the proposed innovation is an approach that not only performs the required tasks but is low in mass (30 kg to 150 kg). Mass constraints make productive excavation challenging. However, innovative designs incorporating transverse bucket-wheels, high payload composite dump beds, and high-speed driving are game changers, enabling regolith operations in low gravity. Phase 1 experimental results show that payload ratio and driving speed govern productivity of small robots. Phase 2 will elevate TRLs from 3 at the beginning to an estimated 4 or 5 at end of contract.