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Designed and built by the Johns Hopkins University Applied Physics Laboratory – with contributions from research institutions and companies around the world – the MESSENGER spacecraft tackles the challenges associated with orbiting Mercury. A ceramic-fabric sunshade, heat radiators, and a mission design that limits time over the planet’s hottest regions protect MESSENGER without expensive and impractical cooling systems. The spacecraft’s graphite composite structure – strong, lightweight, and heat tolerant – is integrated with a low-mass propulsion system that efficiently stores and distributes the approximately 600 kilograms (about 1,320 pounds) of propellant that accounts for 54 % of MESSENGER’s total launch weight.
To fit behind the 2.5-meter by 2-meter (roughly 8-foot by 6-foot) sunshade, MESSENGER’s wiring, electronics, systems, and instruments are packed into a small frame that could fit inside a large sport utility vehicle. And the entire spacecraft is light enough for launch on a Delta II 7925-H (“heavy”) rocket, the largest launch vehicle allowed under NASA’s Discovery Program of lower-cost space science missions.
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