The proposed innovation is an InGaAs-based, radiation-tolerant, micron-gap thermophotovoltaic (MTPV) technology. The use of a micron wide gap between the radiation source and the photovoltaic substantially increases the efficiency of the thermophotovoltaic. This work will be accomplished by combining MicroLink's state-of-the-art InGaAs-based epitaxial lift-off solar cell structure on an InP substrate, and MTPV, LLC's leading-edge, micron-gap thermophotovoltaic device technology. The relevance of this innovation is that it addresses NASA's ongoing need for high-efficiency, lightweight, compact sources power for space vehicles. TPV is an attractive and technically feasible candidate for space power supplies, but its relatively poor efficiency performance has meant that it has not seen widespread use in space applications. However, MTPV technology, by bringing the emitter into the near field of the photovoltaic, couples an order of magnitude more power across the nano-scale vacuum gap than can be absorbed from the far-field spectrum and does so while maintaining the benefits of conventional TPV. MicroLink's ELO growth technology promises to further increase coupled power relative to the current germanium TPV cells while simultaneously reducing substrate costs. Thus, MicroLink ELO and MTPV technology can offer both high efficiency and reasonable cost TPV systems for the first time.