High Temperature Memory Electronics for Long-Lived Venus Missions

The Hot Operating Temperature Technology Program proposal call seeks to advance "high temperature electrical and electronic systems that could be needed for potentially extended in situ missions…". Electronic systems are a core component of any extended mission affecting, e.g., instruments, communications, and operations. In particular, high temperature electronics are needed in order to "mitigate the risks of mission concepts…and expand the range of science that might be achieved with future missions", esp. those in harsh environments. Decadal notes that technology development is critical "for surface access and survivability, particularly for challenging environments such as the surface of Venus". VEXAG similarly emphasizes "Development of high-temperature electronics, sensors…designed for operating in the Venus ambient would be enabling for future missions". Long-lived high temperature electronics have an identified pathway for potential infusion in a future long-lived Venus mission. A Science Mission Directorate project begun in FY17, Long-Life In-situ Solar System Explorer (LLISSE), is developing a functioning prototype of a low-cost scientific probe capable of providing basic but high-value science measurements from the surface of Venus continuously for months or longer. Activities in this project include demonstration of prototype probes designed to withstand the surface conditions of Venus and communicate periodic measurements of temperature, pressure, wind velocity and direction, and chemical composition to an orbiter. These periodic (every 8 hours or better) measurements are over a long duration: a Venus daylight period and the transitions at either end, or approximately 60 Earth days, and provide unique and significant science impact. NASA Glenn Research Center (GRC) has unique capabilities to enable such a mission, and is presently being funded to provide the electronics for LLISSE. This is based on recent breakthroughs in notably expanding electronics capabilities with the world's first microcircuits of moderate complexity that have the potential for sustained operation at 500˚C. Further, operation of these electronics operating for extended periods in-situ in Venus surface atmospheric conditions has also been demonstrated. The electronics for LLISSE includes sensor control and signal processing, power supply management, and communications. The LLISSE approach uses electronics without memory relying on periodic communication of the real-time measured environmental data. This present proposal leverages the electronics development ongoing in LLISSE to address a core capability of broad use, but not part of the LLISSE approach: high temperature memory electronics. The objective is to develop a fully functional 500°C memory packaged circuit operating in-situ for use in long duration Venus missions. The memory is composed of both RAM (Random Access Memory) and ROM (Read Only Memory) chips capable of interfacing with mission control logic and sensors. Both memory types have significant, but different, impact on potential Venus missions. RAM can be written or read as needed for storing and recalling mission data or operations software, while ROM would provide the logic instructions needed for initial power-on or recovery of the mission control logic from serious fault conditions. In particular, this proposed work will develop RAM and ROM technology with supporting electronics with 128 bit and 512 bit capability respectively operable above Venus temperatures (500°C) for at least 3 months, and in Venus surface conditions for 60 days. This work will verify basic compatibility of this memory technology with the system being developed in LLISSE. This work demonstrates for the first time memory electronics operable in Venus surface conditions for extended periods and demonstrates the feasibility of an initial memory "toolbox" for broadening the architecture choices for future missions and decreasing mission risk.