MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) is a NASA Discovery Program mission to the Sun's closest neighbor. Launched on August 3, 2004, the spacecraft must fly in a cruise trajectory for almost seven years, circling the Sun 15 times and traveling approximately five billion miles before finally achieving orbit around Mercury [3]. With six planetary gravitational assists, five large velocity adjustments with its bi-propellant engine, and potentially dozens of smaller maneuvers distributed in between, the cruise phase of the mission is a challenge to the program's scientists, engineers, and planners alike. Flying by Earth once, Venus twice, and Mercury itself three times prior to orbit insertion requires continual re-optimization. Each Mercury flyby is at 200 km from the surface, requiring traditional radiometric, Delta Differential One-Way Ranging, and optical techniques for precision navigation. In order for the spacecraft to operate safely while in orbit around Mercury, at 0.30 to 0.45 AU from the Sun, an innovative sunshade was developed and mounted on its sunward side. However, this constrains the spacecraft attitude to within a 20°×24° operating zone. Science observations, propulsive maneuvers, and all Earth communications must be accomplished in this small Sun Keep-In zone. Launched on a Delta II 7925-H, the spacecraft mass was 54% propellant at liftoff; and throughout the development phase, remaining within the mass budget was a challenge, demanding smart trades in order to meet the mission goals.
MESSENGER - A Highly Constrained Mission to the Innermost Planet
2008-03-01
2051127 byte
Conference paper
Electronic Resource
English
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