Hardware in the loop blended and GPS navigation, acquisition and tracking performance for lunar transfer and return missions

The Space Exploration Initiative (SEI) is driving America's space industry to expand on existing guidance and navigation (G&N) technologies and explore alternative G&N methods. Since the last Apollo mission in 1972, America's space industry has evolved away from manned space missions beyond Earth's orbit. The SEI has altered this trend by. being a catalyst for evaluating, designing, testing and eventually traveling to the Moon and Mars. In order to support this trend and the ever present desire for flight proven hardware that is cost effective and meets the SEI mission goals, this paper evaluates the lunar transfer and return performance of an existing military off the shelf (MOTS) Trimble Force 5 Global Position System (GPS) receiver integrated in a GPS/Inertial Navigation System (INS) navigation system, the Honeywell Space Integrated GPS/INS (SIGI), in a dynamic hardware-in-the-loop (HWIL) test environment. The intent of this paper is to further the research of navigating beyond the GPS satellite constellation's 20,200 km altitude for potentially aiding spacecraft navigation en route to the Moon and its return to Earth. The dynamic HWIL testing with the Force 5 will demonstrate the GPS receiver's navigation, acquisition and tracking performance during the lunar transfer and return phases by focusing on the impact of the satellite transmission patterns and the importance of inertial aiding to the GPS receiver for maintaining GPS observations above the constellation and the ability to acquire and track during reentry through the GPS constellation for the expected mission velocities. The test environment was created with emphasis on the realism of the GPS constellation, impact of dynamics and using real hardware in the loop for testing.