Discovery of FUV and EUV airglow signatures from the thermosphere and ionosphere has been followed by decades of instrumental refinement coupled with pursuit of improved retrieval methods for extracting quantities such as TEC and HmF2. Low-Earth Orbit (LEO) spectrometers and spectral imagers providing regional observations at widely-spaced time intervals can now be supplemented by sensitive instruments in high orbits (GEO). These new imaging systems will generate greatly improved measurements, presenting them in 2-dimensional formats at regular time intervals (~100s) and covering large regions with high spatial resolution. This prospect continues to inspire new work on algorithmic retrievals. The inversion of the 83.4 nm O+ feature on the day side is a longstanding challenge that is now being overcome using new algorithms. Concepts under development use assimilative or empirical models to constrain the solution to a physically realizable subspace; independent data sources can also play a similar role. In addition, targeting of particular parameters for retrieval can optimize the derived information. In combination with retrieval methods developed to maturity in the past, this leads to a concept for a next-generation instrument that will image/monitor the ionosphere from GEO via four spectral signatures, 83.4 nm, 130.4 nm, and 135.6 nm plus an LBH band (155 nm), all with better than 10 km resolution. From this orbit it will deliver high-quality coverage of mid-latitudes. This instrument is under development at NRL, with plans to use the Air Force Space Test Program for mission integration. Innovations in retrieval methods and the status of instrumental will be described, along with how the calculated performance would contribute to the scientific study of mid-latitude phenomena. This work is supported by the Office of Naval Research.