Global Reference Atmospheric Model (GRAM) Series for Aeroassist Applications

Aeroassist is a broad category of advanced transportation technology encompassing aerocapture, aerobraking, aeroentry, precision landing, hazard detection and avoidance, and aerogravity assist. The eight destinations in the Solar System with sufficient atmosphere to enable aeroassist technology are Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Saturn's moon Titan. Engineering-level atmospheric models for five of these targets Earth, Mars, Titan, Neptune, and Venus have been developed at NASA's Marshall Space Flight Center (MSFC). These models are useful as tools in mission planning and systems analysis studies associated with aeroassist applications. This series of models is collectively identified as the Global Reference Atmospheric Model or GRAM series. An important capability of all the models in the GRAM series is their ability to simulate quasi-random perturbations for Monte Carlo analysis in developing guidance, navigation and control algorithms, for aerothermal design, and for other applications sensitive to atmospheric variability. The flexibility of the GRAM series of models is illustrated through recent example applications in aerocapture systems studies and aeroentry studies. These applications, and their role in the development cycle for the various models in the GRAM series, are discussed.